Julie Hunter

Márta Abrusán

Rhetorical Structure and QUDs

We consider two hypotheses about how rhetorical structure and QUD structure might come together to provide a more general pragmatic theory. Taking SDRT ([2]) and some basic principles from [18]'s QUD framework as starting points, we first consider the possibility that rhetorical relations can be modelled as QUDs, and vice versa. We ultimately reject this hypothesis in favor of the possibility that QUDs correspond to topics that bind together the members of complex discourse units.

Theories of rhetorical structure [START_REF] Asher | Logics of Conversation[END_REF][START_REF] Mann | Rhetorical structure theory: Towards a functional theory of text organization[END_REF] and theories of discourse structure centered around a Question Under Discussion or QUD [START_REF] Ginzburg | The interactive stance[END_REF][START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] share many of the same principles. 3 Both approaches hold that the interpretation of a given sentence or elementary discourse unit (EDU) depends in part on that EDU's relation to other moves that have been made in the same discourse. 4 Both also hold that a discourse context must therefore keep track of not only (some subset of the) prior discourse moves but also certain structural relations between these moves. These structural relations are believed to play an integral role in discourse coherence and the relevance of individual discourse moves, and as such, to influence various semantic and pragmatic phenomena, including ellipsis of various sorts, anaphora (rhetorical theories), and prosody (QUD theories).

To clarify their potential contribution to analyses of semantic and pragmatic phenomena, we need a better understanding of how rhetorical and QUD frameworks are related: are they fundamentally distinct, but complementary theories, or do they aim to model the same phenomena? If the latter, do they end up describing two sides of the same coin or are they in conflict? The goal of this paper is to propose and evaluate two hypotheses about how the two frameworks might correspond, so that we can eventually come to a better understanding of the respective roles that these frameworks play with regard to phenomena from the semantics-pragmatics interface. The first hypothesis, which we develop and ultimately reject in §2.1, is that there is a direct correspondence between instances of discourse relations and QUDs in a discourse. The second hypothesis, which we present in §2.2, is that QUDs correspond to complex discourse units in a discourse graph. We judge this hypothesis to be more promising.

Our discussion focusses on two particular theories. On the side of rhetorical structure, we adopt Segmented Discourse Representation Theory [START_REF] Asher | Logics of Conversation[END_REF], which we briefly introduce in §1.1. Of all of the rhetorical theories, SDRT is the most developed from a semantic point of view; it assigns semantics to each of its discourse relations and posits semantic constraints on how its hierarchical discourse representations, which capture the contents of full discourses, can be constructed. These choices are fuelled by concerns about anaphora resolution, presupposition, temporal interpretation and other phenomena relevant to the semantics-pragmatics interface, putting SDRT in an ideal position to be compared to alternative semantic/pragmatic theories of discourse structure. On the side of QUDs, we take inspiration from [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] whose proposal, we think, is closest in spirit to SDRT. Like SDRT it aims to capture relations between discourse moves and provide hierarchical discourse structures that model global features of the discourse context. However, because the account outlined in [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] less thoroughly developed than SDRT, the possible formulations of QUD frameworks that we consider in §1.2 sometimes move beyond basic principles laid out in [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] in directions that we think deserve consideration, but which may not be endorsed by Roberts.

1 Background on SDRT and QUD

A very brief introduction to SDRT

A fundamental principle of rhetorical theories, including SDRT, is that the relations that utterances stand in to one another affect on the one hand the interpretation of the discourse in which the utterances figure and on the other, the interpretation of the utterance contents themselves. Consider (1): [START_REF] Asher | Reference to Abstract Objects in Discourse[END_REF] I missed my meeting this morning. My car broke down.

Seeking a connection between the two parts of (1), an addressee will naturally understand the content of the second sentence as providing an explanation for the content of the first. This interpretation of the discourse comes with its own truth conditions: it is true just in case the speaker was late for her meeting, her car broke down, and the latter event was the cause of the former. At the same time, the inferred causal connection affects the interpretation of the two sentences in [START_REF] Asher | Reference to Abstract Objects in Discourse[END_REF]. Both sentences are in the past tense, which indicates that the events that they describe occurred before the speech time.

The inferred causal relation between the two events entails that in addition, the second event must have occurred before the first-a cause must occur before its effect. This sequence of events does not follow from the tense of the verbs and the order in which the events are described in the discourse, but only from understanding how the two sentences are coherently or rhetorically related. Of course, in the absence of an explicit marker for causality (e.g. because), this causal connection is at best an implicature; nevertheless, speakers regularly accept and act on such implicatures. SDRT aims to model such connections by developing rules for constructing logical forms for discourses and by providing models to interpret these logical forms.

To capture the rhetorical connections in a discourse, rhetorical theories must accomplish three tasks. First, the discourse must be segmented into EDUs according to rules set by the theory. In SDRT, the aim is to have each EDU denote a single eventuality. The next task is to attach each EDU to some other part of the discourse. SDRT maintains that a new move can only be a coherent extension of a given discourse if it is relevant to some other move that has been made previously; thus, each EDU will be attached to at least one other EDU that was discourse prior to it, with the exception of the initial EDU, which will only have attachments to later moves. In this way, a rhetorical relation is a kind of anaphoric relation, but one that holds between discourse units rather than referring expressions and discourse referents. The final task to be accomplished, which is in practice accomplished in tandem with labelling and even segmentation at times, is the labelling of each discourse attachment with a rhetorical relation (Explanation, Elaboration, Contrast, Narration, etc.).

Attachment and labelling involve default reasoning about the contents of the EDUs involved and world knowledge. Importantly, however, they also take into account global features from the discourse. For example, because discourse relations are often implicatures, the inference of an attachment/label that might otherwise be justified can be blocked by information carried by other EDUs in the discourse. For this reason, SDRT provides defeasible rules for inferring discourse relations and stresses the need for global constraints on the development of a discourse structure.

One such global constraint, which affects EDU attachment, is the Right Frontier Constraint (RFC). SDRT, along with other discourse theories [START_REF] Polanyi | A syntactic approach to discourse semantics[END_REF][START_REF] Polanyi | A theory of discourse structure and discourse coherence[END_REF], posits that even if the content of a new EDU satisfies the semantic conditions for being attached to some other EDU in a discourse, this connection is only coherent if the prior EDU is accessible SDRT defines the RF so as to reflect facts about accessibility like those illustrated in (2-a)-(2-c). We start by introducing SDRT's discourse structures, which are connected graphs rather than trees. Graphs are needed to model certain facts about discourse, two of which are relevant for this paper: (i) some units can have incoming links from two different EDUs, and (ii) multiple DUs can work together to form a complex discourse unit (CDU), which serves as a single argument to a discourse relation.

(3) a. Sam is being punished. π1 She took her parents' car without permission, π2 so they've grounded her for 2 weeks. π3 b.

Explanation (π 1 , π 2 ), Result (π 2 , π 3 ), Elaboration (π 1 , π 3 ) (4)
a. π 1 + π 2 , but their parents don't speak any foreign languages.

π 3 b. Continuation(π 1 , π 2 ), Contrast ([π 1 , π 2 ], π 3 )
In (3), π 3 is the second argument for an instance of Result and an instance of Elaboration, whose first arguments are distinct. In (4), which builds on π 1 and π 2 from (2-b), not only are both π 1 and π 2 needed to provide the necessary antecedent for their in π 3 , but these units are attached to each other and both satisfy the conditions needed to support the Contrast with π 3 . SDRT would therefore group them into a single, though internally complex, argument for Contrast. SDRT's graphs thus contain two types of edges: (i) edges that are labelled with discourse relations, and (ii) edges that relate each CDU to each DU that it contains. Edges of type (i) can be further subdivided into subordinating and coordinating edges, governed by the semantics of the relations that label these edges. When a DU is attached to another DU via a subordinating relation, both arguments remain accessible for further attachments. In (2-c), for example, the role of π 2 is to provide background information that explains how John came to speak German (π 1 ) or to simply back up that claim. π 1 therefore remains central to the discussion and salient enough to be accessible to π 3 despite the intervening π 2 . Subordinating relations include Explanation, Elaboration, Background, and Question-Answer Pair, among others. When a DU is attached to another DU via a coordinating relation, the RF is pushed dynamically forward so that the second DU is on the RF, but the first is knocked off. In (2-b), for instance, π 2 goes on to tell us that John's sister speaks French, so the discourse is no longer centered on John's German speaking abilities when it comes time to add π 3 . An attachment from π 3 to π 1 is thus difficult to achieve. Coordinating relations include Contrast, Continuation, Narration (Sequence), Result, and Conditional, among others.

We conclude with a description of SDRT's RF. A node π x is on the RF of a graph G, i.e. RF G (π x ), just in case (a) π x is Last, i.e. π x is the EDU introduced most recently into G following the textual order of the EDUs in G, or (b) ∃π y (RF G (π y )) such that (i) e s (π x , π y ) for a subordinating edge e s or (ii) π y ∈ π x (i.e., π x is a CDU). The Right Frontier Constraint (RFC) simply states that an incoming EDU that needs to be attached to a graph G should be attached to a node along the RF.

QUD

The concept of a QUD is not a homogenous one; we will aim in this section to clarify two ways of understanding this concept from the literature. Perhaps the widest application of QUD has been in the context of focus phenomena ( [START_REF] Beaver | Sense and Sensitivity[END_REF][START_REF] Büring | On d-trees, beans, and b-accents[END_REF][START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF]). Consider ( 5) and ( 6) (where the capital letters indicate the desired intonational emphasis):

(5) a. John gave the cake to TOM. b. John gave the CAKE to Tom.

(5-a) and (5-b) have the same syntactic structure and the same truth conditions: each is true just in case John gave the cake in question to Tom. Yet utterances of (5-a) and (5-b) are not appropriate in the same contexts. (5-a), for example, would be an appropriate answer to the question (Q1) To whom did John give the cake? but not to (Q2) What did John give to Tom?;

(5-b) would be an appropriate answer to (Q2) but not to (Q1). [START_REF] Rooth | A theory of focus interpretation[END_REF] proposed that focus is licensed if there is a suitable set of anaphorically available alternative propositions in the context. Since questions are standardly analysed as introducing a set of alternative questions (Alt-Q) (cf. [START_REF] Hamblin | Questions in Montague English[END_REF]), the anaphoric requirement of focus can be satisfied by a congruent question, a question whose alternative set Alt-Q is a subset of Alt-F. The Alt-F sets for (5-a) and (5-b) are as follows: [START_REF] Büring | On d-trees, beans, and b-accents[END_REF] a. Alt-F of (5-a)={x ∈ D e : John gave the cake to x} b. Alt-F of (5-b)={x ∈ D e : John gave x to Tom} (Q1) is a suitable antecedent for the alternatives introduced by (5-a) but not by (5-b) because Alt-(Q1)={x ∈ D e : John gave the cake to x} is a subset of Alt-F of (5-a) but not Alt-F of (5-b). Conversely, (Q2) is a suitable antecedent for (5-b) but not (5-a).

Sometimes the QUD for a discourse can be a sub-question of a larger question that needs to be addressed, as illustrated in [START_REF] Carlson | Dialogue games: an approach to discourse analysis[END_REF]. Such hierarchical structures or stacks of questions have been proposed by [21, ?,?,?], among others. [START_REF] Carlson | Dialogue games: an approach to discourse analysis[END_REF] John gave the CAKE to [Tom] CT and the ICE cream to [Linda] CT .

[6] would analyze [START_REF] Carlson | Dialogue games: an approach to discourse analysis[END_REF] as follows. The first unit can be taken to answer the question (Q3) What did John give to Tom?, and the second, the question (Q4) What did John give to Linda?. The presence of contrastive topic marking on Tom and Linda indicates that the two questions should be understood as addressing the super-question (Q5), John gave what to whom?. In this case, (Q3) and (Q4) form a strategy for answering (Q5). The QUD for an utterance u is always the open question that is the most salient at the time u is made. Thus (Q3) is the QUD for John gave the CAKE to Tom, but once this question has been answered, the next subquestion of (Q5), namely (Q4), is addressed.

While the above notion notion of QUD is helpful for the analysis of focus, contrastive topic and other focus-related phenomena, it is a very local notion in the sense that it cannot tell us what accounts for the incoherence of the following mini-discourse: [START_REF] Ginzburg | The interactive stance[END_REF] JOHN ate the beans. My sister is a NURSE. Rose was gone for 10 MINutes!

We can retrieve a QUD for each sentence in (8) based on its focus structure: Who ate the beans?, What does your sister do?, and How long was Rose gone?, respectively. Moreover, each sentence provides a complete answer to its QUD, so moving from one sentence to the next should be a perfectly fine strategy. Yet ( 8) is not a good discourse.

[18] aims to push the notion of QUD further in order to account for the felicity of the focus of utterances in the contexts in which they are actually used. In a nutshell: the sentences in [START_REF] Ginzburg | The interactive stance[END_REF] do not hang together well because we do not understand them as participating in a strategy to answer the same, larger question. In more detail, [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] posits that the structure of open questions in a discourse can be represented with a stack. In [START_REF] Carlson | Dialogue games: an approach to discourse analysis[END_REF], for example, when (Q3) is the QUD, it is on the top of the stack, just above (Q5). Once (Q3) is answered, it is popped from the stack and (Q4) is pushed on to the top. Once all sub-questions of (Q5) have been addressed, and (Q5) has therefore been answered, (Q5) is also pushed from the stack. The heart of Roberts's idea is to push the stack paradigm further: don't assume in a discourse like ( 7) that (Q5) is the question on the bottom. In a real discourse, (Q5) would in turn figure in a strategy to answer a yet larger question, and so on, all leading up (or down) to the Big Question: What is the way things are?. Of course, the Big Question is far too large to answer in one discourse, so interlocutors adopt the strategy of breaking it down into smaller questions. Exactly which sub-questions are relevant in a given discourse are determined by the conversational goals of the interlocutors; the sub-questions chosen signify a strategy for achieving this goal. 6 What is wrong with (8), then, is that it's not clear what subquestion of the Big Question is at issue; the individual segments do not form a clear strategy for answering an obvious question.

The rules of the language game constrain how different types of linguistic structures update the discourse context, with the following principal effects: (a) If an assertion is accepted by the interlocutors in a discourse, it is added to the common ground. (b) If a question is accepted by the interlocutors in a discourse, then it is added to the set of questions under discussion, and it becomes the immediate topic of the discussion. This in turn commits the interlocutors to a common goal, namely, finding the answer. By the principle of Relevance (described in (9) below), the interlocutors should attempt to answer the question as soon as it is asked. A member of the set of questions under discussion in a discourse is removed from that set iff its answer is entailed by the common ground or it is determined to be unanswerable. [START_REF] Grice | Studies in the way of words[END_REF] A move m is Relevant to the question under discussion q, i.e., to last(QUD(m)), iff m either introduces a partial answer to q (m is an assertion) or is part of a strategy to answer q (m is a question). ( [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF], p. 21)

As a result of the above rules, all discourse moves must be relevant to the QUD, though they need not all answer (completely or partially) the QUD: it is enough if they are part of the strategy for answering the QUD.

2 Locating the correspondence [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] has hypothesized that rhetorical theories and QUD-based theories are compatible and that understanding how they work together might give us a more complete pragmatic theory. The goal of this paper is to determine, on the assumption that both theories are correct, how the theories might be related. We assume that they cannot be independent: if a discourse move m n , say, explains the content of a prior discourse move m k , and both m n and m k are relevant to the QUD, then the fact that m n explains m k should also be relevant to the QUD-relating relevant discourse moves in irrelevant or off-topic ways would presumably lead to a very odd discourse. In other words, we assume that if the two are compatible, the discourse structures predicted by QUD-theories should correspond in some way to the structures posited by SDRT, such that the discourse graph for a whole discourse should shed light on the question structure for that discourse.

In what follows we explore two hypotheses about how the theories might be related: the first, which we will reject, assumes that rhetorical relations correspond to QUDs; the second, which will be shown to be more promising, assumes that QUDs can be associated with complex discourse units in SDRT graphs.

Rhetorical relations as QUDs

An intuitive starting point for the comparison of SDRT and QUD is the hypothesis that rhetorical relations can be analyzed as QUDs, and vice versa. For example, when two discourse units, π i and π j , are related by Narration, the QUD associated with π i , to which π j would provide an answer, would be What happened next?. Similarly, if π i and π j are related by Explanation, the QUD associated with π i , to which π j would provide an answer, would be Why?. This hypothesis, which casts SDRT and QUD as two sides of the same coin, is frequently raised in our discussions with colleagues on this topic, and it appears to inform the work of [START_REF] Van Kuppevelt | Directionality in discourse: Prominence differences in subordination relations1[END_REF] and [START_REF] Onea | Potential Questions in Discourse and Grammar[END_REF].

We call the hypothesis that there is a one-to-one correspondence between discourse relation tokens and QUDs (or, more precisely, that each relation instance can be analyzed as a QUD at the point that the relation is added to the graph) R-QUD:

(10)
R-QUD: For discourse units π i and π j and rhetorical relation R in an SDRT graph, if R(π i ,π j ), then there is some question QUD(π i ) that π i gives rise to and that π j answers fully or partially.

Structural correspondence. R-QUD also suggests a structural correspondence between the hierarchical structures of SDRT and those of QUD. The hierarchical structures in SDRT, for example, are fully determined by the instances of rhetorical relations in the discourse, so if each rhetorical relation in an SDRT graph corresponds to a question in the QUD structure for the same discourse, then we might expect the set of questions to display a hierarchical structure that echoes that of the SDRT graph. This expectation is reinforced by the fact that SDRT's Right Frontier (RF) and Roberts's QUD stacks reflect (a part of) the hierarchical structure of a discourse and are designed to perform the same task, namely that of tracking live and salient issues in a discourse. Indeed, the two structures are similar, at least at first glance. The RF of a graph G consists of the last EDU introduced in G as well as any DU that is super-ordinate to a node on the RF via a chain of subordinating relations. Likewise, a QUD stack will include the most recent open question introduced in the discourse as well as any question that is a super-question of a question on the stack via a chain ordered by the sub-question relation. 7 In SDRT, a new DU in a graph G that attaches to a node m along the RF of G will knock any other node that is subordinate to m off of the RF. Similarly, a new question Q in a QUD stack S that is a sub-question of another question Q m on the stack, entails that any question Q n , such that Q n is higher on S than Q m be popped from the stack (unless Q is a sub-question of Q n as well). Finally, both SDRT and QUD posit constraints that require new moves to attach to/address a move on the RF/stack. Despite these apparent similarities, there are also some obvious, and deep, dissimilarities between the RF and stacks. Most notably, the RF orders DUs, not relations, while a QUD stack orders questions, not answers. Given that R-QUD associates relations and questions (and the arguments to relations with answers), R-QUD will inevitably limit the role that either QUD stack or the the RF can play in determining the coherence and relevance of discourse moves. From the point of view of QUD, a new move, m, in a discourse d must be relevant to one of the open questions on the QUD-stack for d at the time that m is made. Yet if we assume R-QUD and SDRT's RF, then the nature and order of the open questions on a QUD stack for a discourse d would themselves be derived through rhetorical reasoning-there are no independent principles that would lead to exactly this set of questions for d in exactly the desired order. From the perspective of SDRT, a new EDU e in a discourse d must be attachable to some node along the RF of the graph for d at the time that the utterance that introduces e into the discourse is made. Yet if we assume R-QUD and QUD stacks, then coherence and relevance cannot be driven by the arguments to the rhetorical relations, for these correspond to answers not questions on the QUD stack. Given R-QUD, then, QUD and SDRT must be understood as giving two very different and incompatible models of what drives coherence and relevance in discourse.

Another structural consequence of assuming SDRT and R-QUD would be that the stack derived from the RF of a given discourse graph would not necessarily be ordered by the sub-question relation. (And conversely, a consequence of assuming QUD and R-QUD would be that the relations connecting nodes along the RF would be severely limited by the sub-question ordering on the QUD stacks.) Again, it is in part the QUD and the need to answer that QUD that is supposed to determine whether a given discourse move is coherent or not in a QUD framework; the sub-question relation is important because it keeps conversation on topic by simply breaking down the QUD into smaller QUDs. Examples like [START_REF] Hamblin | Questions in Montague English[END_REF] show, however, that a combination of R-QUD and SDRT exclude the possibility of a QUD stack ordered by the sub-question relation. [START_REF] Hamblin | Questions in Montague English[END_REF] We had so much fun in London! π1 We got to see the Lion King! π2 I've been wanting to go for a really long time π3 and my mom finally gave me tickets for my birthday! π4 We also got to ride on the big Ferris wheel π5 ... SDRT would predict the following structure for (11):

(11)' Elaboration(π 1 , π 2 ), Background(π 2 , [π 3 , π 4 ]), Continuation(π 3 , π 4 ), Elaboration(π 1 , π 5 ), Continuation(π 2 , π 5 ).

From the first two relation instances, R-QUD would yield questions: (q1) What did you do? and (q2) What makes that so exciting? (or something like that). Suppose we stack these questions so that (q2), the more discourse-recent question, is on top of (q1). The fact that we (eventually) have Elaboration(π 1 , π 5 ) and Continuation(π 2 , π 5 ) shows that (q1), What did you do?, has not yet been fully answered when π 3 and π 4 are uttered, so it must still be on the stack of open questions. (q2), however, is not a subquestion of (q1). Still, the utterances of π 3 and π 4 are coherent and relevant in the discourse.

A third consequence of R-QUD is that it would result in a loss of information for SDRT. A node in an SDRT graph, as noted in section 1.1, can have incoming links from two different nodes, though it is unclear how such dependencies could be modelled using stacks. In (3), repeated here, π 2 appears to explain π 1 , and so could be taken to answer the question (q1) Why? (or Why is Sam being punished?), while π 3 appears to elaborate on π 1 , and so could be taken to answer the question (q2) How is Sam being punished?. At the same time, π 3 also describes a result of π 2 and so could be taken to answer the question (q3) what happened as a result? or something like that.

(3)

Sam is being punished. π1 She took her parents' car without permission, π2 so they've grounded her for 2 weeks. π3

The stack architecture does not tell us where (q3) fits in to the stack; stacks are more naturally compatible with a tree-based structure, not the graph-based structure of SDRT.

Nor does the stack architecture predict that reversing the order of (q1) and (q2) (and so that of π 2 and π 3 ) would make a difference to the discourse content, though clearly such a reversal would make a significant impact. Another source of information loss for SDRT, given R-QUD, relates to CDUs. The need for CDUs is illustrated in ( 12): [START_REF] Lewis | Scorekeeping in a language game[END_REF] I finally figured out the right baking process for cannelés. π1 I left them at 210 for 20 minutes, π2 then I turned them down to 190 for 30 minutes, π3 and then I finished at 180 for the last 15 minutes. π4

In ( 12), π 2 -π 4 together describe the correct baking process introduced in π 1 ; no single unit alone provides this information. In terms of questions, no single unit answers the question: What is the right baking process?. In other words, π 2 -π 4 form a CDU that serves as the second argument to the Elaboration relation that intuitively holds between π 1 and π 2 -π 4 . At the same time, the CDU composed of π 2 -π 4 has its own internal structure. Its component EDUs are related by Narration or Sequence, which imposes temporal constraints on the EDUs-the cooking steps cannot be followed in just any order. QUD stacks derived through R-QUD (or otherwise) do not provide the structure needed to capture the layers of discourse graphs that result from CDUs.

Relation instances. Even if we abandon a correspondence between the RF and stacks (which would render R-QUD far less interesting), the correspondence posited in R-QUD breaks down for several reasons. First, for certain rhetorical relations at least, we run into a problem of circularity in which the intuitive question has to mention the associated discourse relation or marker directly. For example, SDRT would posit the relation Contrast(π 1 , π 2 ) for ( 13), but it's unclear what question could replace the Contrast relation that wouldn't itself presuppose the same rhetorical relation. [START_REF] Mann | Rhetorical structure theory: Towards a functional theory of text organization[END_REF] [Pat] F came to the party π1 but [Mel] F didn't. π2

The most suitable implicit question to posit in this case would be What does π 1 contrast with?. Similar remarks can be made for instances of Parallel, Result (What happened as a result?/And so?), and Narration (What happened then/next/after that?). This calls into question the possibility of truly translating relations into independent questions. An alternative question for [START_REF] Mann | Rhetorical structure theory: Towards a functional theory of text organization[END_REF], which would be more in line with the ideas presented in [START_REF] Roberts | Context in dynamic interpretation[END_REF] and [START_REF] Büring | On d-trees, beans, and b-accents[END_REF], is that π 1 and π 2 in (13) could be taken as addressing the same question Who came to the party?. Yet the fact that π 1 and π 2 both answer the same question doesn't justify the use of the contrastive marker but. In fact, a variant of [START_REF] Mann | Rhetorical structure theory: Towards a functional theory of text organization[END_REF] in which but is replaced by and, and π 1 and π 2 are related with Parallel, is acceptable as well, though the intuitive background question for such a variant would be the same: Who came to the party?. Similar remarks can be made for certain examples of Contrast that have possible Continuation-based variants. For instance, (14-a) and (14-b) could both be understood as answering the question: What's going on with John?, but this doesn't capture the intuitive difference between the examples, brought about by the presence of the contrastive marker in (14-a). [START_REF] Onea | Potential Questions in Discourse and Grammar[END_REF] a. John called but he said he's running late.

b. John called and he said he's running late.

In sum, if we assume R-QUD, the QUD framework runs into a problem because it does not easily extend to handle most co-ordinating relations.

Summary. The forgoing discussion reveals that a correspondence like that assumed by R-QUD would lead to a loss of information and an abandonment of basic principles from both SDRT and QUD. From the point of view of SDRT, if we assume R-QUD and QUD, then we must abandon the role that rhetorical reasoning plays in determining the coherence and relevance of individual discourse moves. We also lose information because QUD is not designed to handle triangular discourse structures (like that underlying (3)), CDUs, or coordinating relations. Nor is the correspondence posited by R-QUD favorable for QUD. If we assume SDRT + R-QUD, we must abandon the hypothesis that QUD-stacks of the sort posited in [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] guide the coherence and relevance of individual discourse moves. Moreover, the QUDs predicted from R-QUD would not look like the QUDs that a QUD-framework would predict otherwise. In [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] and elsewhere, it is suggested that focus marking indicates the QUD. In the case of ( 15), the second sentence has focus marking, but the question that can be derived from this marking (What did John buy?) is much more fine-grained than the question type that seems to correspond to the rhetorical relation Elaboration (e.g., Can you tell me more?). In fact, the question generated from focus is compatible with many rhetorical relations. [START_REF] Polanyi | A theory of discourse structure and discourse coherence[END_REF] John went to the store (π 1 ). He bought [apples] F (π 2 ).

Mary is mad at John (π 1 ). He bought [apples] F (π 2 ). (instead of pears.)

SDRT would posit Elaboration(π 1 , π 2 ) for ( 15), but Explanation(π 1 , π 2 ) in ( 16). Yet in both cases, the question generated from the focus structure of π 2 is: What did John buy? Thus, in adopting R-QUD, we lose information from QUD as well.

Complex discourse units as QUDs

In this section, we take a step back and consider another hypothesis about how SDRT and QUD might interact. One of the intuitions behind [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF]'s QUD account is that QUD stacks model the plan structure of a discourse. The rough idea is that given a specific discourse goal, which either triggers a QUD or is itself modelled as a QUD, a speaker or set of interlocutors will aim to answer this QUD by breaking it down in smaller and smaller QUDs until the QUDs become more manageable. As these smaller QUDs are answered, their collective answers work together to provide answers to larger QUDs and so on until the QUD triggered by the original discourse goal is answered. The question that we pose in this section is whether there are features of an SDRT graph that might reveal the planning structure of a discourse, yielding a correspondence more in touch with the planning aspect of [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF]'s QUD stacks. The hypothesis that we consider is that CDUs and the relations between them yield the desired planning structure. In short, the idea is that CDUs manifest a certain topical cohesion that allows us to treat their contents as complex answers to implicit questions.

CDUs. A CDU, as briefly described in §1.1, is a collection of discourse units (EDUs, CDUs or a mixture of both) that work together to function as an individual argument to a discourse relation. (4) provides an example of a CDU in a Contrast relation; [START_REF] Lewis | Scorekeeping in a language game[END_REF] provides an example in an Elaboration relation. Further empirical motivation for CDUs comes from the behavior of anaphora: [START_REF] Roberts | Context in dynamic interpretation[END_REF] One plaintiff was passed over for promotion three times (π 1 ). Another didn't get a raise for five years (π 2 ). A third plaintiff was given a lower wage compared to males who were doing the same work (π 3 ). But the jury did not believe this (π 4 ). ( [START_REF] Asher | Logics of Conversation[END_REF], p. 15)

As noted in [START_REF] Asher | Logics of Conversation[END_REF], the anaphor this in π 4 can be resolved to π 3 or to the set {π 1 , π 2 , π 3 }, but not to, say, π 2 alone. The second interpretation of [START_REF] Roberts | Context in dynamic interpretation[END_REF], represented in Figure 1, requires the construction of a CDU π t(1-3) formed from {π 1 , π 2 , π 3 }. Thus CDUs are constructed when called for by the demands of rhetorical relations or anaphora, but we can also think of CDUs in a more general way as collections of DUs that share a thematic or rhetorical coherence. Suppose that two people are discussing a recent democratic presidential debate in the U.S. and one speaker is arguing that Bernie Sanders won the debate. She might provide a multi-step argument for her position, providing numerous justifications for it and elaborating on each justification in turn. We can think of her whole argument as yielding one large CDU whose members work together to provide support for the claim that Bernie Sanders won. Within this larger CDU, each justification for her main position will also yield a CDU whose members are the set of DUs that participate in the argument for this justification. For example, the speaker might offer as justification of her main claim the argument that Sanders provided a superior plan for attacking Wall Street. The members of the CDU associated with this justification would be the set of DUs that work together to support the claim that Sanders provided a superior plan for Wall Street. Within this CDU, the speaker might go on to provide multiple reasons for why Sanders' plan was superior, thereby giving rise to smaller CDUs and so on.

In this way, we can think of each CDU in a discourse as having a topic that glues its members together, 8 although the topic of a given CDU is not (necessarily) derivable from the content of any explicit move in the discourse; it is rather a topic that emerges from considering what the discourse moves work together to accomplish. In addition, because CDUs are collections of connected DUs-i.e. not just arbitrary sets of DUs from the discourse-the set of CDUs in a discourse will naturally give rise to a partial order based on the subset relation: if a CDU π i includes a CDU π j , the set of members of π j will be a strict subset of the set of members of π i . A CDU cannot merely overlap another CDU without one being entirely included in the other. CDU-QUD. We summarize the hypothesis that the content of a CDU fully answers an implicit QUD as follows: [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] CDU-QUD a : For every CDU π i in an SDRT graph there is some question QUD(π i ) that the the discourse units in π i answer fully. 9To illustrate the correspondence, consider the textbook example [START_REF] Rooth | A theory of focus interpretation[END_REF] and the associated SDRT graph in Figure 2.

(

) 19
John had a great evening (π 1 ). He had a great meal (π 2 ). He ate salmon (π 3 ). He devoured lots of cheese (π 4 ). Then he won a dancing competition (π 5 ). Putting aside deeper questions about how exactly to predict the construction of CDUs and their associated implicit topics, which would be an interesting topic for future research, let us assume that there are three CDUs in this structure: π t(1-5)10 , i.e., the discourse as a whole, π t(2-5) , and π t [START_REF] Asher | Discourse topic[END_REF][START_REF] Asher | Subordinating and coordinating discourse relations[END_REF] . We derive π t(2-5) from the fact that if π 2 participates in the second argument of an Elaboration relation off of π 1 , then π t(3-4) does as well because π t(3-4) is simply an Elaboration of π 2 . These three CDUs can each be associated with a question as follows:

1. π t(1-5) is associated with a Q 1 , e.g.: What was John's evening like? 2. π t(2-5) is associated with a Q 2 , e.g.: What did he do in the evening? 3. π t(3-4) is associated with a Q 3 , e.g.: What did he eat? Note that the CDUs posited for [START_REF] Rooth | A theory of focus interpretation[END_REF] are ordered by the subset relation (if π i ∈ π t(3-4) , then π i ∈ π t(2-5) , etc.). This relation is moreover reflected in what appears to be a sub-question relation that holds between Q 1 , Q 2 , and Q 3 (if an assertion answers Q 3 , it partially answers Q 2 , etc.).

Given the correspondence between the CDU structure of ( 19) and the proposed associated QUD structure, a reasonable hypothesis is that we can extend the correspondence posited by CDU-QUD a with CDU-QUD b . ( 20 There are two CDUs in the above structure: π t(1-3) and π t(2-3) . Because π t(1-3) is simply the graph as a whole, π t(2-3) is a subset of π t(1-3) . CDU-QUD b therefore predicts that the question associated with π t(2-3) will be a sub-question of the question associated with π t(1-3) . This is incorrect: π t(1-3) would intuitively be associated with a question such as What did John do yesterday?, while π t(2-3) would likely be associated with a question such as Why did he do this?. Yet the latter question is not a sub-question of the former. Because the structure of the attachment between π t(1-5) and π t(2-5) in ( 19) is identical to the structure of the attachments in ( 21) and ( 22), the sub-question relation posited by CDU-QUD b to hold between QUDs is not entailed by the structural relations in the discourse graph. The nature of the rhetorical relations, which are represented by the labels of the structural relations, must also be taken into account. As a result, CDU-QUD b is probably only applicable when the CDU π 2 (from the definition of CDU-QUD b ) attaches to the top node of the CDU π 1 with a relation that implies subeventhood. The semantics of the Elaboration relation, for example, entails that the eventuality described by the second argument of an Elaboration is a sub-eventuality of the eventuality described by the first.

Future directions. If the applicability of CDU-QUD b is indeed as restricted as the preceding discussion suggests, then this hypothesis entails that many QUDs derived from CDU-QUD a will not be linked to other QUDs semantically, though QUDs might still be ordered by a precedence relation. This is an unsatisfying result because it potentially prevents many QUDs in a discourse from working with other QUDs to form a plan or strategy for achieving a discourse goal.

One way to save the idea of a CDU-QUD correspondence, which we ultimately find promising for at least certain kinds of discourse, is to loosen the requirement on the QUD side that QUDs be ordered by the sub-question relation and allow strategies for achieving discourse goals to be more complex than sequences of sub-questions. That is, we should abandon CDU-QUD b and replace is with a more general hypothesis. One idea, given the proposed correspondence in CDU-QUD a , is that a QUD might be retrieved from the rhetorical structure of a discourse much like a question can be retrieved from focus structure in frameworks like [START_REF] Beaver | Sense and Sensitivity[END_REF][START_REF] Büring | On d-trees, beans, and b-accents[END_REF] and [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF]. After all, CDUs are sets of connected nodes from a discourse graph, so the possible CDUs for a given disourse must be determined by the rhetorical connections at work in the discourse.

Associating QUDs with CDUs could have a value for SDRT as well. In particular, QUDs could be used to capture the topical cohesion of CDUs. This would give us a means for abstracting over the details of an SDRT graph to look at the higher-level strategy that a speaker, or group of interlocutors, has adopted to achieve her/their discourse goal. We assume that this strategy will be apparent at least in cooperative, informationseeking discourses.

This high-level approach to thinking about the relation between QUDs, strategies for achieving discourse goals, and rhetorical structure reflects, we think, the spirit of [START_REF] Roberts | Context in dynamic interpretation[END_REF] (last paragraph before the conclusion) and [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] (pp. 62-63) where the idea that each explicit move in a discourse should address a QUD, as suggested by R-QUD, is de-emphasized or outright rejected, and it is suggested that the connection between the rhetorical structure of larger chunks of discourse and strategies for achieving discourse goals should should be further explored. Future work on the connection between CDUs and QUDs will depend, however, on these notions being more clearly defined in their respective frameworks than they currently are. What we suggest is that these aspects of QUD and SDRT might most beneficially be developed in tandem.

Conclusion

Adopting SDRT and some basic notions from [START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF]'s QUD framework as starting points, we have explored two hypotheses about how rhetorical structure and QUD structure might come together to provide a more general pragmatic theory. The first hypothesis, which posits a correspondence between rhetorical relations and QUDs, was rejected. The second hypothesis posits a correspondence between QUDs and more global features of an SDRT graph, namely how discourse units are thematically grouped together into larger, complex chunks of discourse. This hypothesis is, we have argued, more promising.

Fig. 1 .

 1 Fig.1. SDRT graph for[START_REF] Roberts | Context in dynamic interpretation[END_REF]

Fig. 2 .

 2 Fig.2. SDRT graph for[START_REF] Rooth | A theory of focus interpretation[END_REF]

  He can translate for you while you're in Berlin.] π 3 c. [John speaks German.] π 1 [(because) He lived in Stuttgart for 10 years.] π 2 [He can translate for you while you're in Berlin.] π 3

	While π 1 and π 2 in (2-a) are related by Result-a connection supported by the con-
	tents of the EDUs and world knowledge about what being able to translate in Berlin
	would normally require-the same connection is blocked for π 1 and π 3 in (2-b). (2-c),
	however, shows that it is not blocked by just any intervening EDUs.

5

, that is, if it is on the Right Frontier (RF). Compare (2-a)-(2-c):

(2) a. [John speaks German.] π1 [He can translate for you while you're in Berlin.] π2 b. [John speaks German] π 1 [and his sister speaks French.] π 2 ?? [

)

  CDU-QUD b : If a CDU π 2 is a member of another CDU π 1 then QUD(π 2 ) is a subquestion of QUD(π i ) CDU-QUD b runs into problems when we consider a wider range of rhetorical relations than the ones in the above example, however. As mentioned above, π t(3-4) figures in π t(2-5) because π t(3-4) is related to π 2 via an Elaboration relation. This Elaboration relation in turn naturally gives rise to a set of questions ordered by the sub-question relation: even once we get down to π t(3-4) , we're still talking about John's evening. The situation is less clear for CDUs figuring in other subordinating relations, e.g. Explanation, Consequence, Commentary, and so on.Consider[START_REF] Van Kuppevelt | Directionality in discourse: Prominence differences in subordination relations1[END_REF] and its discourse graph in Figure3, in which the topic of the CDU provides an Explanation for π 1 :[START_REF] Van Kuppevelt | Directionality in discourse: Prominence differences in subordination relations1[END_REF] Yesterday John and his wife went to the fanciest restaurant in Paris (π 1 ). It was John's birthday (π 2 ) and his wife wanted to spoil him (π 3 ).

		π1(restaurant)
		Explanation
		π t(2-3)
	π2(birthday)	Result	π3(spoil)
		Fig. 3. SDRT graph for (21)

  Structurally (22) is like[START_REF] Van Kuppevelt | Directionality in discourse: Prominence differences in subordination relations1[END_REF]; only the rhetorical relations are different. Again, the question intuitively associated with π t(2-3) (e.g. What was the economists reaction to this?) does not seem to be a sub-question of the question associated with the whole graph (e.g. What did the FED do today?).

			π1(F ED)
		Commentary
			π t(2-3)
	π2(skepticism)	Contrast	π3(f ear)
			Fig. 4. SDRT graph for (22)
		22) illustrates the same point but with a different discourse relation:
	(22)	The Fed lowered the prime interest again today for the third time in a month
		(π 1 ). Most economists greeted the move with skepticism (π 2 ) but were afraid
		to express this publicly (π 3 ). (Modified version of example (5) from [4])

SDRT does allow for violations of the RFC in cases that[START_REF] Asher | Reference to Abstract Objects in Discourse[END_REF] calls discourse subordination, but such violations need to be explicitly signalled, e.g. Let's go back to your first point.

That the conversational goals and intentions of speakers are relevant for computing the pragmatic meaning of an utterance goes back at least to[START_REF] Grice | Studies in the way of words[END_REF]. See also[START_REF] Grosz | Attention, intentions, and the structure of discourse[END_REF][START_REF] Thomason | Accommodation, meaning, and implicature: interdisciplinary foundations for pragmatics[END_REF]

, 7], and[START_REF] Lewis | Scorekeeping in a language game[END_REF]. See[START_REF] Ginzburg | The interactive stance[END_REF] for a QUD-based theory that shares many features with[START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF], but is importantly different in ways we cannot consider in this paper.

This is the ordering adopted by[START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF] on page 15, clause (g.iii).

Though see[START_REF] Asher | Discourse topic[END_REF] for a discussion of the difficulties of defining discourse topic in SDRT.

Although what counts as a 'full' answer can depend on the context and interlocutors' interests as in[START_REF] Roberts | Information structure in discourse: Towards an integrated formal theory of pragmatics[END_REF].

The CDU that represents the discourse as a whole is identical to the discourse graph as a whole, so we do not use special notation to label it.

We gratefully acknowledge support from the ERC grant 269427 and Marie Curie FP7 Grant, PCIG13-GA-2013-618550.


Nicole Abdou

Bruno Alonso

Nicolas Brun

Sabine Devautour Vinot

Matthieu Paillet

Perine Landois

Ahmad Mehdi

Peter Hesemann
email: peter.hesemann@umontpellier.fr

Confinement Effects on the Ionic Liquid Dynamics in Ionosilica Ionogels: Impact of the Ionosilica Nature and the Host/Guest Ratio

Keywords: Ionosilica, ionogels, sol-gel process, confinement, solid-state NMR spectroscopy, Raman spectroscopy, ionic conductivity

ABSTRACT

Ionosilica ionogels have been lately introduced as emerging all-ionic designer materials. They consist of an ionic liquid (IL) guest trapped within a solid ionosilica support host. In this work, we investigate the influence of the (i) ionosilica nature and (ii) the ionosilica/IL ratio on the mobility of the confined IL. We report the elaboration of various ionosilica ionogels via a nonhydrolytic sol-gel process, using namely tris (3-(trimethoxysilyl)propyl)amine (TTA), Methyl-tris (3-(trimethoxysilyl)propyl)ammonium iodide (MTTA) and tetrakis (3-(trimethoxysilyl)-propyl)ammonium iodide (TKTA) as ionosilica precursors, with the IL butylmethyl imidazolium bis-triflimide ([BMIM] TFSI). Various ionogels were prepared from different ratios between the ionosilica host and the IL guest. The host/guest interactions i.e. the change in the conformational contribution of the IL counter-anion were explored by means of Raman spectroscopy. In addition, the transport properties of the confined species were probed via spin echo solid-state NMR experiments and Complex Impedance Spectroscopy (CIS) measurements. Raman experiments revealed different conformational equilibrium for the TFSI anion in the various ionosilica ionogels, with an increase in the cisoid form compared to the bulk IL due to confinement effects. The TFSI anion seems to experience different degree of confinement and thus different interactions with the ionosilica scaffold as a function of the investigated parameters. Concomitantly, the 1 H spin echo NMR and CIS measurements revealed a significantly higher ionic mobility in the materials synthesized in the presence of the tristrialkoxysilylated ammonium precursor compared to the one synthesized in the presence of tetratrialkoxysilylated ammonium precursor. These results may reflect stronger host-guest interactions in the latter case related to the higher degree of reticulation of the network. All these techniques give concordant results and highlight an effect of the chemical constitution of the ionosilica scaffold and the amount of confined IL on its dynamics within the network.

Introduction

Ionic liquids (ILs) are salts displaying melting temperatures lower than 100 °C. Due to their purely ionic constitution, ILs display unique physical and physico-chemical properties such as high ion conductivities over large temperature ranges (including very low temperatures), large liquidus ranges, low flammability, and high electrochemical stability. ILs have been subject of intense research and found applications in various areas, e.g. energy storage, 1 catalysis, [START_REF] Pârvulescu | Catalysis in Ionic Liquids[END_REF][START_REF] Hallett | Room-Temperature Ionic Liquids: Solvents for Synthesis and Catalysis. 2[END_REF] gas adsorption [START_REF] Hasib-Ur-Rahman | Ionic liquids for CO2 capture-Development and progress[END_REF] and so on. The advantageous properties of ILs have recently opened the route toward commercial applications in various technologies. [START_REF] Shiflett | Commercial Applications of Ionic Liquids[END_REF] One of the key characteristics of ILs is their liquid state at room temperature or slightly above.

This feature makes the integration of ILs in devices like batteries or membranes challenging.

One solution to solve this problem is the use of ionogels (IGs) rather than pure ILs. [START_REF] Bideau | Ionogels, ionic liquid based hybrid materials[END_REF] Ionogels consist of ionic liquids that are confined in a solid host matrix, with the principal aim to confer to the material the physico-chemical properties of the pure IL while modulating favorably its mechanical properties. [START_REF] Susan | Ion gels prepared by in situ radical polymerization of vinyl monomers in an ionic liquid and their characterization as polymer electrolytes[END_REF] Ionogels are currently considered as a particularly innovative class of functional composite materials, [START_REF] Tome | Emerging iongel materials towards applications in energy and bioelectronics[END_REF] with high flexibility to tune their mechanical, morphological, textural, electrical, … properties.

The characteristics of ionogels are principally governed by two parameters: (i) the nature of the IL guest and (ii) the characteristics of the host matrix. Whereas a large diversity of ILs exist and can directly be implemented in ionogels' formation, the design of a suitable scaffold also affects strongly the properties of the entire system. It appears crucial to design scaffold materials that interact favorably with the IL guest in order to improve the overall properties of the resulting composites, for example in view of an enhancement of their ionic conductivity in the area of energy storage materials. [START_REF] Taylor | Fully-Zwitterionic Polymer-Supported lonogel Electrolytes Featuring a Hydrophobic Ionic Liquid[END_REF] In this context, ionosilicas, i.e., silica hybrid materials constituted of ionic building blocks, appeared as a particularly promising class of host materials for IL confinement. Ionosilicas combine the morphological and textural polyvalence of silica with the chemical versatility of ionic liquids. They can be obtained in a large variety of morphologies such as powders, monoliths and nanoparticles, [START_REF] Nguyen | Nanostructured polysilsesquioxanes bearing amine and ammonium groups by micelle templating using anionic surfactants[END_REF][START_REF] Rodrigues | Controlled synthesis and osmotic properties of ionosilica nanoparticles[END_REF][START_REF] Sauvanier | Simple and Straightforward Synthesis of Porous Ionosilica for Efficient Chromate Adsorption[END_REF] and additionally display a high chemical polyvalence due to the presence of covalently immobilized ionic groups. So far, we particularly focused on applications of ionosilicas in separation and extraction, as for example in anion exchange, [START_REF] Thach | Ionosilicas as efficient sorbents for anionic contaminants: Radiolytic stability and ion capacity[END_REF][START_REF] Bouchal | Ionosilicas as efficient adsorbents for the separation of diclofenac and sulindac from aqueous media[END_REF][START_REF] Thach | Surface Properties and Chemical Constitution as Crucial Parameters for the Sorption Properties of Ionosilicas: The Case of Chromate Adsorption[END_REF] where ionosilicas display high affinities toward various types of anionic species such as oxo-anions, drugs and dyes, but also towards biopolymers such as siRNA. [START_REF] Bouchal | Biocompatible Periodic Mesoporous lonosilica Nanoparticles with Ammonium Walls: Application to Drug Delivery[END_REF][START_REF] Daurat | Organosilica Nanoparticles for Gemcitabine Monophosphate Delivery in Cancer Cells[END_REF][START_REF] Mezghrani | Periodic Mesoporous Ionosilica Nanoparticles for Green Light Photodynamic Therapy and Photochemical Internalization of siRNA[END_REF] Furthermore, ionosilicas are a highly polyvalent class of materials that can be obtained from various ionosilica precursors, [START_REF] Hesemann | Precursor Mediated Synthesis of Nanostructured Silicas: From Precursor-Surfactant Ion Pairs to Structured Materials[END_REF] and the interface properties of ionosilicas can efficiently be tuned both via the anion and the cation, resulting in a remarkable diversity of materials with tunable interface properties. [START_REF] Thach | Tuning the Interfacial Properties of Mesoporous lonosilicas: Effect of Cationic Precursor and Counter Anion[END_REF] More recently, we used ionosilicas as host matrix to immobilize ILs. [START_REF] Abdou | Ionic Guest in Ionic Host: Ionosilica Ionogel Composites via Ionic Liquid Confinement in Ionosilica Supports[END_REF] Silica based ionogels could be obtained in highly straightforward one step procedures via non-hydrolytic synthesis strategies starting from ionosilica precursors in IL media, in the presence of formic acid. [START_REF] Sharp | A Two-Component, Non-Aqueous Route to Silica Gel[END_REF][START_REF] Dai | Preparation of silica aerogel using ionic liquids as solvents[END_REF][START_REF] Martinelli | An investigation of the sol-gel process in ionic liquidsilica gels by time resolved Raman and H-1 NMR spectroscopy[END_REF][START_REF] Viau | Ionic Liquid Mediated Sol-Gel Synthesis in the Presence of Water or Formic Acid: Which Synthesis for Which Material?[END_REF] We applied this synthesis strategy for the formation of all-ionic composites starting from silylated ionic precursors. In these ionosilica ionogels, particular confinement effects could be observed between the ionic host matrix and IL host, highlighting the outstanding appeal of ionosilicas for the design of IL-containing composites. As an example, ionosilica ionogels can contain up to 80

wt.-% of IL while maintaining a mechanically robust and self-standing morphology. Besides this purely quantitative aspect, we could hereby show that the chemical nature of the support is of considerable significance for the elaboration of composite materials with tailored properties. We therefore took benefit of the high versatility of ionosilicas, allowing an efficient control of texture, architecture and chemical constitution of the host material, in order to optimize the properties of the resulting ionosilica ionogel.

In this work, we explore the influence of the constitution of the ionosilica precursor and thus the nature of the ionosilica matrix on the dynamics of the confined IL [BMIM]TFSI. Therefore, three different ionosilica precursors were used for the elaboration of ionosilica ionogels using different ionosilica/IL ratios. We investigate host-guest interactions via the determination of the conformational change of the TFSI anion in the various ionosilica ionogels via Raman spectroscopy experiments. crucial dependence between the nature of the ionosilica scaffold, the ionosilica/IL ratio and the IL dynamics. The obtained results highlight an efficient control and tuning of the ionic transport properties of ionosilica ionogel materials that can be of high interest in energy storage domains.

Experimental section

The ionosilica precursors tris (3-(trimethoxysilyl)propyl)amine (TTA), Methyl-tris (3-(trimethoxysilyl)propyl)ammonium iodide (MTTA) and Tetrakis (3-(trimethoxysilyl)propyl)ammonium iodide (TKTA) (figure 1) were synthesized following previously described protocols. [START_REF] Nguyen | Nanostructured polysilsesquioxanes bearing amine and ammonium groups by micelle templating using anionic surfactants[END_REF] 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]TFSI) was purchased from IoLiTec. Formic acid (p.a.) was purchased from VWR. All chemicals were used as received. The synthesis of various ionosilica ionogels was performed in one-pot synthesis involving ionosilica precursor, formic acid and the IL. The ionosilica matrices were formed via nonhydrolytic sol-gel procedure from the trialcoxysilylated amine precursors in the presence of IL.

First, the ionosilica precursor was mixed and vigorously stirred for three minutes with

[BMIM]TFSI in a Pyrex glass tube using a vortex apparatus. Then, the polycondensation reaction was initiated by adding formic acid to the mixture. After complete addition, the mixture was stirred two minutes until the formation of a homogeneous solution. Monoliths were obtained after 24 hours at room temperature. The exact quantities of the reactants used for the synthesis of the ionosilica ionogels are given in table kHz. The chemical shift was referenced using Adamantane as a secondary reference (peak at 1.8 ppm). The acquisition window is 100 kHz and no line broadening has been applied. [START_REF] Watanabe | Application of Ionic Liquids to Energy Storage and Conversion Materials and Devices[END_REF] H transverse relaxation times T 2 ' were estimated using Hahn echoes with incremented inter-pulse delays.

Raman spectroscopy: Raman measurements were performed on a Fourier transform Raman spectrometer (Bruker RFS100) in the macro configuration with an excitation wavelength of 1064 nm and an impinging power of about 150 mW.

Complex Impedance Spectroscopy (CIS):

Impedance measurements were carried out using a Solartron analytical Modulab XM MTS. An ac voltage of 20 mV was applied over a frequency domain from f = 1 Hz to f = 1 MHz, at fixed temperature in 273 K -393 K range. Measurements were carried out with anhydrous solids, after heating the materials at 373 K overnight, followed by several helium purges in order to eliminate residual solvent within the composites. Under these conditions and according to TGA results (figure S7), the solid is fully dehydrated without any traces of formic acid while preventing the IL release. About 75 mg of the powder sample was introduced in a home-made sample holder, i.e. between two gold electrodes, in a parallel plate capacitor configuration, with an annular Teflon spacer to avoid short circuits and insure insulation. This configuration corresponds to the basic "two-probe" method for the electrical measurements. The sample surface was deduced from the surface of the smallest electrode, while the sample thickness was evaluated by subtracting the length of the empty sample holder and that of the filled one using a Vernier caliper.

The conductivity was determined considering the value collected at the dc plateau in the Bode representation of the real part of the conductivity. Typically, the real part of the ac conductivity results from the combination of three contributions:

(1)

The polarization component σ'(ω,T), corresponding to the increasing part of the signal at high frequency, arises from the local rearrangement of charges or dipoles causing dipolar reorientation. The dc conductivity plateau σ dc (T), resulting from the long-range redistribution of charges dominates the intermediate frequency region. In case of highly ionic conductive materials, the Maxwell Wagner Sillars contribution σ MWS (ω,T) due to the ionic charge accumulation to the sample/electrode interface is observed at low frequency. In insulators, σ MWS (ω,T) ≈ 0 and σ dc (T) ≈ 0 and only the polarization conductivity is detectable.

Results and Discussion

Our special concern is the design of novel ionogel materials with optimized properties using tailor-made scaffold hosts and IL guests. In this context, we recently reported novel ionosilica ionogels and demonstrated particular confinement effects between an ionosilica host formed from the tris-trialkoxysilylated ammonium precursor TTA and the ionic liquid [BMIM]TFSI guest in these phases. The material was formed in a straightforward synthesis process only involving the TTA precursor, the [BMIM]TFSI IL and formic acid. Under these conditions, the tertiary amine group of the TTA precursor is protonated to H-TTA and forms ionic ammonium formate entities, simultaneously to the sol-gel process. This feature has been experimentally demonstrated in a previous study. [START_REF] Abdou | Ionic Guest in Ionic Host: Ionosilica Ionogel Composites via Ionic Liquid Confinement in Ionosilica Supports[END_REF] The final material is therefore an ionosilica constituted of ammonium formate groups. As reported before, the confined IL within this ionic host matrix forms two distinct populations: (i) the first one interacting with the pore walls via electrostatic interactions and (ii) the second one, forming bulk-like IL domains. [START_REF] Abdou | Ionic Guest in Ionic Host: Ionosilica Ionogel Composites via Ionic Liquid Confinement in Ionosilica Supports[END_REF] In this work, we focus on the variation of the host matrix in order to monitor the impact of the constitution of the scaffold on the physico-chemical properties of the ionosilica ionogels materials and in particular on the ion mobility of the confined IL. For this purpose, various ionosilica ionogels were synthesized via non-hydrolytic sol-gel procedure from the ionosilica precursors TTA, MTTA and TKTA (Fig. 1) in the presence of variable quantities of the IL

[BMIM]TFSI. The conformational change of the ionic species upon confinement is assessed via Raman spectroscopy, and the ionic mobilities of the IL are evaluated via 1 H solid state NMR spectroscopy and Complex Impedance Spectroscopy (CIS) measurements. We determined particularly the mobility of the IL guest as function of (i) the molecular structure of the ionosilica host matrix and (ii) the amount of the confined IL.

The TFSI anion of the confined IL ([BMIM]TFSI) used in this study is one of the most commonly used anions in ILs. Its flexibility on a molecular scale is reflected by its easy conversion between the cisoid and transoid conformers displaying C 1 and C 2 symmetry, respectively (Fig. 2). The two conformers present distinct signatures in the Raman spectra in the 250-380 cm -1 range. [START_REF] Martinelli | Conformational evolution of TFSI-in protic and aprotic ionic liquids[END_REF] The ratio between the two conformers depends on the local environment and may reflect its direct surroundings on a molecular level, e.g. with the ionosilica matrix.

Whereas a nearly 1 : 1 ratio between the conformers can be found in the IL bulk, [START_REF] Herstedt | Spectroscopic characterization of the conformational states of the bis (trifluoromethanesulfonyl)imide anion (TFSI -)[END_REF] higher C 1 /C 2 ratios indicate stronger host-guest interactions. The cis-trans ratio of the TFSI anion therefore give an indication between confined and bulk populations of the TFSI anion (Fig. 2). The vibrational bands found in the analyzed region can be attributed to the twisting (τ) and rocking (ρ) modes of the SO 2 and CF 3 groups of the TFSI anion. [START_REF] Rey | Spectroscopic and theoretical study of (CF 3 SO 2 )(2)N -(TFSI -) and (CF 3 SO 2 )(2)NH (HTFSI)[END_REF] According to Herstedt et al.,

the bands at about 306, 326 and 333 cm -1 can be used as C 1 indicators, whereas the bands at about 298, 314 and 339 cm -1 are characteristic for the C 2 conformer. [START_REF] Herstedt | Spectroscopic characterization of the conformational states of the bis (trifluoromethanesulfonyl)imide anion (TFSI -)[END_REF][START_REF] Martinelli | Conformational Changes and Phase Behaviour in the Protic Ionic Liquid 1-Ethylimidazolium Bis(trifluoromethylsulfonyl)imide in the Bulk and Nano-Confined State[END_REF] Although not being a

C 2 conformer (trans) C 1 conformer (cis)
quantitative method, the deconvolution of the spectra allows the determination of the ratio between the two conformers. [START_REF] Martinelli | Conformational evolution of TFSI-in protic and aprotic ionic liquids[END_REF] The results of the Raman spectra fitting for the materials (x= 1, 3, 6 and 12) are shown in figure 3b. The contribution of C 1 and C 2 conformers were estimated following the equations 2 and 3:

[C 1 ]= (2) [C 2 ]= (3)
Where I x designates the integrated Raman intensity of a band centered at about wavenumber x and designates the sum of the integrated intensities of all bands at about 298, 306, 314, 326, 333 and 339 cm -1 . The relative contributions of the C 1 and C 2 conformers obtained from this procedure for the different ionosilica ionogels are summarized in table 2. For the series of ionosilica ionogels , synthesized in the presence of variable amounts of

[BMIM]TFSI (x = 1, 3, 6, 12), the C 1 contribution remains always higher than the reference value Th 1 , that is the C 1 contribution in the bulk IL (49%), whereas the C 2 remains always lower than Th 2 (C 2 contribution in the bulk = 51.0%). When the amount of confined IL increases within the material, the C 1 contribution progressively decreases from 59.0% for to 50.5% for . This general increase in the C 1 contribution of the confined TFSI anion with respect to the bulk IL can clearly be associated to the confinement of the IL within the composite, i.e. to host guest interactions with the ionosilica matrix. For this reason, the highest contribution of the Furthermore, a clear impact of the nature of the ionosilica matrix on the C 1 /C 2 ratio could also be observed. For a similar amount of incorporated IL (e.g. 1 mL), the material synthesized using the TKTA precursor shows the highest contribution of the C 1 conformer (68.5 %) compared to the one obtained from the MTTA and the TTA precursors (59.0 and 55.0 %, respectively). This trend that was also observed in the series of materials synthesized in the presence of 3 and 6 mL of IL, points more pronounced host-guest interactions in the materials obtained from the TKTA and MTTA precursors. The effect attenuates in the materials synthesized in the presence of 12 mL, where the C 1 /C 2 ratio almost reaches the value observed in the bulk IL whatever the ionosilica matrix (figure 4). The observed increase of the C 1 conformational contribution reflects increasing host-guest interactions in the series of the materials < < . The reduced IL-scaffold interactions in the case of may be attributed to a larger "accessible-IL" volume (i.e. less reticulated network) and thus to a lower surface-bounded/ bulk-like IL populations ratio, whereas the IL in the case of , the materials undergo stronger confinement effects due to the presence of a fourth crosslinking knot within the ionic building blocks.

Materials show intermediate behavior explained by the substitution of the proton ( ) by a more bulky methyl group (figure 1).

To confirm these results, we have also carried out the analysis of the Raman spectra following the approach reported by Wu et al. . [START_REF] Wu | Combined Raman Scattering and X-ray Diffraction Study of Phase Transition of the Ionic Liquid BMIM TFSI Under High Pressure[END_REF] These authors used the bands at about 312, 326 and 405 cm -1 and about 295, 339 and 396 cm -1 to reveal the ratios between the C 1 and the C 2 conformer (figures S4-S5 and table S1). The trends observed regarding the evolution of the C 1 /C 2 ratio as a function of the ionosilica scaffold and the IL content of the materials are coherent with the analysis discussed before (vide supra). Raman spectroscopy therefore gives a clear indication for the evolution of the C 1 /C 2 conformer ratio, and also reveals significant differences between the three investigated host matrices, thus highlighting modulable host-guest interactions in these systems.

To further investigate the IL confinement effect within the ionosilica host matrix, 1 H solidstate NMR spectroscopy experiments were performed. The 1 H MAS NMR spectra of the ground monoliths are represented in figure 5a. All spectra show the characteristic signals of the imidazolium cation with highly variable peak widths and overlapping the broader peaks of the MT matrix. The full width at half maximum (FWHM) value of all peaks decreases gradually when the concentration of the IL increases. [START_REF] Echelmeyer | Novel Ternary Composite Electrolytes: Li Ion Conducting Ionic Liquids in Silica Glass[END_REF][START_REF] Noda | Pulsed-gradient spin-echo H-1 and F-19 NMR ionic diffusion coefficient, viscosity, and ionic conductivity of non-chloroaluminate roomtemperature ionic liquids[END_REF] Similar results were observed for all ionosilica ionogel materials and (figure S6).

The observed decrease in the FWHM of the peaks is a direct response to the dynamics of the mobile liquid phase within the solid matrix. [START_REF] Nayeri | Surface effects on the structure and mobility of the ionic liquid C(6)C(1)ImTFSI in silica gels[END_REF] Therefore, in order to obtain further insight in the mobility of the confined IL, we determined the average transverse relaxation times T 2 ' of Our results show that the T 2 ' values gradually increases with the increase in the amount of confined IL for all ionosilica ionogels, as for example from 3.6 ms for to 19.0 ms for a b

for the materials obtained from the MTTA precursor. The obtained results are in accordance with the decrease in the FWHM observed in 1 H solid-state MAS spectra. Higher T 2 ' values therefore suggest increasing mobilities of the confined IL (vide infra). On the other side, the T 2 ' values also depend on the ionosilica matrix. Generally speaking, the T 2 ' values are the highest in the materials constituted of a TS matrix and the lowest in the materials based on a TK matrix.

For example, for the materials synthesized in the presence of 6 mL of IL using the different ionosilica precursors, the T 2 ' value decreases from 13.7 ms for the material to 9.7 ms for material to reach a minimum value of 6.9 ms for material. This trend can be observed for all other series of ionosilica ionogel materials synthesized with different amounts of IL.

The large variations in T 2 ' observed as function of the amount of confined IL or the nature of the scaffold can be related to variations in effective homonuclear 1 H-1 H dipolar couplings D HH , here the main contributions to transverse relaxation mechanism. Therefore, the increase in T 2 ' is related to a decrease in D HH that can be explained by increased degrees of motion for the IL.

These findings elucidate the imidazolium cation dynamics relatively to the amount of the confined IL and the nature of the ionosilica scaffold and are in line with the results obtained in Raman experiments. Furthermore, the observed results suggest the presence of a labile proton, enhancing the mobility of the confined IL in the case of . The protonation of the ionosilica matrix in the case of or an interaction between the IL and the (N-H) group might yield additional H + ions that contribute to the increased IL dynamics. Whereas being constituted of tetraalkylammonium building blocks undergo a decrease in the IL mobility due the increased crosslinking within the network.

The electrical properties of the pure ionosilica matrices and the corresponding composites were evaluated by CIS. As illustrated in figure S8, the Bode representation of the conductivity for the pure TS ionosilica matrix is dominated by the polarization conductivity, resulting from the dipolar relaxation of polar components of the polymer. The very low conductivity values coupled with the absence of the dc conductivity contribution indicates that TS matrix is an insulator, suggesting that the formate species cannot diffuse over long distances without the assistance of guest charge carriers. For the MT and TK ionosilica matrices, conductivity values are at least one order of magnitude higher compared to that recorded on TS, while remaining very low.

Accordingly, the dc conductivity response is only observable at temperature higher than 343 K and 363 K for MT (figure S8) and TK (figure S9) matrices respectively. This trend evidences that iodide ions are slightly more mobile than formate species, even though they still require guest species to be efficiently transported within the MT and TK matrices.

On the opposite, the The dc conductivity values were then evaluated in the frequency independent domain of ) (  ac at each temperature and further discussed according to the IL content and the ionosilica nature.

For the series of ionosilica ionogels synthesized in the presence of variable amounts of

[BMIM]TFSI (x = 1, 3, 6, 12) (figure 6a), the dc conductivity is boosted with increasing the IL content, i.e. with increasing the charge carriers concentration. Accordingly, displays the best performances: its  dc values are four orders of magnitude higher than those recorded for . The raise of the conductivity with IL increase is also observed for both other series of ionosilicas (see figures S14 and S15). It relies on the monotonous change of the ratio between the two guest populations while increasing the IL concentration. [START_REF] Abdou | Ionic Guest in Ionic Host: Ionosilica Ionogel Composites via Ionic Liquid Confinement in Ionosilica Supports[END_REF][START_REF] Iacob | Enhanced charge transport in nano-confined ionic liquids[END_REF][START_REF] Vioux | From Ionogels to Biredox Ionic Liquids: Some Emerging Opportunities for Electrochemical Energy Storage and Conversion Devices[END_REF] The first one refers to the interfacial layer composed of ILs interacting with the pore walls via electrostatic interactions, which prevails at low IL concentration. This host-guest interaction makes the dynamics of the a b system slowed down because of the dominating population of IL in cis conformation, as evidenced in Raman spectroscopy. [START_REF] Martinelli | Conformational evolution of TFSI-in protic and aprotic ionic liquids[END_REF][START_REF] Nayeri | Surface effects on the structure and mobility of the ionic liquid C(6)C(1)ImTFSI in silica gels[END_REF] The second population which becomes significant at high IL loading, is associated with the bulk-like IL population localized in the center of the porosity.

Compared to the IL population interacting with the pore walls, the viscosity of the system decreases and merge toward that of the bulk IL, improving the dynamics of the system, as reported for composites resulting from ILs supported in various porous solids. [START_REF] Macfarlane | Ionic liquids and their solid-state analogues as materials for energy generation and storage[END_REF][START_REF] Bideau | Effect of confinement on ionic liquids dynamics in monolithic silica ionogels: H-1 NMR study[END_REF][START_REF] Singh | Ionic liquids confined in porous matrices: Physicochemical properties and applications[END_REF][START_REF] Noor | Ionogels based on ionic liquids as potential highly conductive solid state electrolytes[END_REF][START_REF] Guyomard-Lack | Destructuring ionic liquids in ionogels: enhanced fragility for solid devices[END_REF][START_REF] Yoshida | Superionic Conduction over a Wide Temperature Range in a Metal-Organic Framework Impregnated with Ionic Liquids[END_REF] As a support, the conductivity of recorded at 333 K ( dc = 8.13 x 10 -3 S.cm -1 , see Table 3) is consistent with the value reported for the bulk BMim]TFSI ( dc = 8.00 x 10 -3 S.cm -1 ). [START_REF] Vranes | Physicochemical Characterization of 1-Butyl-3-methylimidazolium and 1-Butyl-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide[END_REF] In addition, the electrical properties of the ionosilica ionogels are equally impacted by the nature of the ionosilica precursor. At fixed IL content, the conductivity performance of the composites follows the > > sequence (see Figure 6b). This sequence remains valid whatever the IL concentration, x, and further agrees with the conclusions deduced from NMR and Raman analysis. It evidences specific (i) host/guest interactions and/or (ii) typical conduction pathways for the charge carriers diffusion within the host matrix according to the ionosilica precursor. Noteworthy, the series displays the lowest conductivity values, in relation with the four cross-linking knots involved in the TKTA precursor, which makes the polymer highly rigid and further impedes the movements of the guest species. On the opposite, the high conductivity values recorded on the composites reveals that the pathway for the ions transfer inside the polymeric host is favored by the less steric H-TTA precursor, creating free volume large enough to achieve less constrained dynamics of the IL than in . Based on this, composites show an intermediate behavior, in relation with the bulkier methyl group of MTTA replacing the hydrogen of (N-H) groups of the H-TTA precursor of the series.

In the case of , one also notes that the interaction between IL and the (N-H) group of the H-TTA precursor might also produce additional H + ions that could participate to the ion conduction process, [START_REF] Vavra | Transport Properties and Local Structure of an Imidazole/Protic Ionic Liquid Mixture Confined in the Mesopores of Hydrophobic Silica[END_REF] magnifying the conductivity performances recorded on this series of composites.

Conclusion

In this work, we investigated the influence of (i) the nature of the ionosilica scaffold and the (ii) ionosilica/IL ratio on the mobility of the confined IL. Therefore, various ionosilica ionogel composites were synthesized evolving three different ionosilica precursors with different amounts of confined IL. Three characterization techniques were used to elucidate the host-guest interactions and thus the IL dynamics within the systems: Raman spectroscopy, 1 H solid-state NMR and Complex Impedance Spectroscopies.

Raman experiments reveal stronger host/guest interactions in the materials compared to the ones due to a higher crosslinking degree in the latter. Furthermore, significant increase in the transoid form was noticed relative to the decrease in the host/guest ratio. This increase reflects a reduce host-guest interactions with the increase in bulk-like IL fraction within the ionosilica scaffold. Concomitantly, 1 H solid-state spin echo NMR and CIS measurements suggest that the IL dynamics within composites is strongly dependent of the scaffold nature and the host/guest ratio. At fixed IL content, the IL dynamics within the network follows the > > sequence. The observed result can be explained by (i) the existence of a labile (N-H) proton in the case of which may create additional charge carriers contributing to the increased conductivity of the system and (ii) the presence of a fourth crosslinking knot in the case of composites impeding the local movement of the mobile guest species. Additionally, the results show an increase in the IL dynamics with the decrease in the ionosilica content relative to the increase in the bulk-like IL population within the network. Accordingly, the dynamics of IL in reaches that of the bulk demonstrating the particular confinement of the IL within the ionosilica matrix which allows the preservation of the IL properties while trapped within a solid scaffold.

This possibility to significantly enhance the ionic mobility by tuning the nature of ionosilica scaffold and the amount confined IL highlights the unique and interesting properties of ionosilica ionogel composites. These designer solid materials may be of high interest for many applications in different fields, e.g. as solid electrolyte in the energy storage domain.

Figure 1

 1 Figure 1 Molecular structures of the three ionosilica precursors tris(3-(trimethoxysilyl)propyl)amine (TTA), methyl-tris(3-(trimethoxysilyl)propyl)ammonium iodide (MTTA) and tetrakis(3-(trimethoxysilyl)propyl)ammonium iodide (TKTA). Note that the protonation of the TTA precursor occurs during the synthesis of the ionosilica ionogels in the presence of formic acid, yielding H-TTA as represented above.

Figure 2

 2 Figure 2 Scheme of the two conformers of the TFSI anion (N: blue, S: orange, O: red, C: grey, F: yellow).

Figure 3

 3 Figure 3 (a) Raman spectra of the ground monoliths in the range of 225-425 cm -1 , (b) Fitted Raman spectra of the ground monoliths in the 250-380 cm -1 range showing the contribution of TFSI anion conformers in the obtained ionosilica ionogels as function of the amount of incorporated IL. Hollow black circles represent experimental data, solid gray line result of the global fit using nine Lorentzian components and red solid (resp. grey dashed) lines highlight the bands attributed to the C 1 (resp. C 2 ) components.

C 1

 1 conformer was observed with the material containing the lowest amount of IL , and b a almost reaches the value observed in the bulk for the material synthesized with the highest IL quantities ( ). The increase of the contribution of the C 2 conformer can therefore be attributed to an enhancement of the bulk fraction of the confined IL. Similar trends are observed for and materials.

Figure 4

 4 Figure 4 Relative contributions of TFSI C 1 and C 2 conformers estimated using the analysis of the Raman spectra (see main text) in the obtained ionosilica ionogels as function of the incorporated IL amount and the molecular structure of ionosilica matrix

imidazolium 1 H

 1 signals from spin echo decays. The spin echo NMR sequence measures an exponential decay known as the relaxation time T 2 ' by acquiring the NMR signals for different spacing of the two pulses (echo time). The 1 H T 2 ' values of the -C 1 H and -C 5 H located at 0.7 ppm and 7.3 ppm are summarized in table S2 (ESI). The evolution of the T 2 ' values as function of the volume of the IL and the nature of the ionosilica scaffold is represented in figure 5b.

Figure 5

 5 Figure 5 (a) 1 H solid-state MAS NMR spectra of ground monoliths ( MAS = 20 kHz) and (b) T 2 'values as function of the volume of the IL of the different ionosilica ionogels for the peak at 0.7 ppm.

  -Wagner Sillars, dc and polarization conductivity contributions for and , while the Maxwell-Wagner Sillars contribution is missing for , in agreement with the lower conductivity displayed by this composite. The diffusion conductivity plateau observed once the IL is incorporated inside the ionosilica matrix underlines that  dc is assigned to the IL dynamics. IL participates to the conductivity process as a charge carrier and by providing additional ions.[START_REF] Iacob | Enhanced charge transport in nano-confined ionic liquids[END_REF][START_REF] Neouze | A route to heat resistant solid membranes with performances of liquid electrolytes[END_REF]

Figure 6

 6 Figure 6 (a) Temperature dependence of the dc conductivity for the ionosilica ionogels synthesized using TTA precursor in the presence of variable amount of [BMIM]TFSI. (b) Temperature dependence of the dc conductivity for the ionosilica ionogels synthesized in the presence of variable amount of [BMIM]TFSI

  1 H solid-state NMR and Complex Impedance Spectroscopy experiments elucidate the IL dynamics upon confinement. Altogether, these analyses reveal a

Table 1

 1 1. The obtained monoliths were kept at 80°C overnight in order to eliminate residual volatiles (HCOOH, HCOOCH 3 , H 2 O, CH 3 OH, etc.). The ionosilica Used quantities for the synthesis of the ionosilica ionogel materials.

	monoliths	obtained	from	TTA,	MTTA	and	TKTA	are	labelled
	,	and	respectively, where x is initial volume of the IL in mL.
	TTA	IL	FA		MTT	IL	FA	TKTA	IL	FA
					A
	n(mmol)	n(mmol)	n(mmol)		n(mmol)	n(mmol)	n(mmol)		n(mmol)	n(mmol)	n(mmol)
	6	3	54		6	3	54		6	3	72
	6	10	54		6	10	54		6	10	72
	6	20	54		6	20	54		6	20	72
	6	41	54		6	41	54		6	41	72

Solid-state NMR spectroscopy:

[START_REF] Watanabe | Application of Ionic Liquids to Energy Storage and Conversion Materials and Devices[END_REF]

H solid-state Nuclear Magnetic Resonance NMR spectra were recorded at ν 0 ( 1 H) ≡ 600.1 MHz on a VARIAN VNMR 600 spectrometer fitted with a Varian HX MAS probe using 3.2 mm ZrO 2 rotors. 1D measurements were carried out at 20°C with a π/2 pulse of 4 µs and a recycling delay of 10 s. The samples were analyzed under MAS at ν MAS

= 20

Table 2 :

 2 Percentage contributions of the two conformers C 1 and C

2 estimated from Raman spectra fitting and equations (2) and (3).

Table 3 :

 3 Diffusion conductivity values recorded at 333 K for the series of ionosilica ionogels.

	σ dc	σ dc	σ dc
	(S.cm -1 )	(S.cm -1 )	(S.cm -1 )
	1.62x10 -7	5.08x10 -9	5.25x10 -10
	2.88x10 -5	2.23x10 -7	7.07x10 -8
	7.94x10 -4	5.25x10 -5	2.75x10 -5
	8.13x10 -3	5.01x10 -4	7.41x10 -4

Acknowledgements

This work was supported by a doctoral fellowship of the 'Ecole Doctorale 459 -Sciences Chimiques Balard' (N. A.). We thank for the excellent technical assistance of Luc Chavignon for the Raman experiments, Philippe Gaveau and Emmanuel Fernandez for solid state NMR measurements and Amine Geneste for CIS measurements.

Supporting Information

Electronic supplementary information (ESI) available. See DOI: XXX  Ionosilica precursors detailed synthesis.

 Liquid NMR spectra of the ionosilica precursors.

 Supplementary Raman spectra for and .

 C 1 /C 2 conformers contribution following the approach reported by Wu et al.. [START_REF] Wu | Combined Raman Scattering and X-ray Diffraction Study of Phase Transition of the Ionic Liquid BMIM TFSI Under High Pressure[END_REF]  1 H NMR MAS spectra of and monoliths.

 TGA curve of monolith after 12 hours at 100°C.

 Supplementary Bode representation of the conductivity in the 273 K-393 K temperature range.

 Supplementary temperature dependence of the dc conductivity for and monoliths.

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Notes

The authors declare no competing financial interest.


Descatha Alexis
email: <alexis.descatha@rpc.aphp.fr>

Roquelaure Yves

Jean-Fran Chastang

Evanoff Bradley

Diane Cyr

Annette Leclerc

Work, a prognosis factor for upper extremity musculoskeletal disorders?

Keywords: musculoskeletal diseases, upper extremity, work, prognosis factor

Upper extremity musculoskeletal (UEMS) disorders are an important problem in industrial countries

There is strong evidence for

 [START_REF] Buckle | Work-related neck and upper limb musculoskeletal disorders[END_REF]an association between biomechanical exposures and UEMS disorders.

However, little is known about the occupational factors [START_REF] Hagberg | Wells R Work related musculoskeletal disorders (WMSDs). A reference book for prevention[END_REF][START_REF] Roquelaure | Active epidemiological surveillance of musculoskeletal disorders in a shoe factory[END_REF][START_REF] Bernard | Musculoskeletal disorders and workplace factors: a critical review of epidemiologic evidence for work-related musculoskeletal disorders of the neck, the upper-limb, and low back[END_REF] associated with recovery of these disorders. [START_REF] Cole | Prognosis of nonspecific work-related musculoskeletal disorders of the neck and upper extremity[END_REF][START_REF] Hagberg | Clinical assessment, prognosis and return to work with reference to work related neck and upper limb disorders[END_REF][START_REF] Kuijpers | A prediction rule for shoulder pain related sick leave: a prospective cohort study[END_REF] To determine if occupational factors were associated with the outcome in workers with UEMS symptoms or disorders, we used data from the repetitive task survey performed in 1993 1994 and again in 1996 1997. The design has been described in earlier publications. ,

- - [8
Each worker had a standardized medical examination at baseline and again in 1996 1997. The self-administered questionnaire filled out 9] at baseline included personal variables, a psychological variable, postures and biomechanical constraints at work (self-assessed, but checked with the occupational physician), psychosocial work factors, and baseline severity of the disorders. Workers were also asked in 1996 1997 about changes in work tasks in the three year follow-up period.

-Only workers with symptoms or UEMS disorders in 1993 1994 are considered here. Three categories of outcome in 1996 1997 were -defined: no symptoms and no UEMS disorders, UEMS symptoms and no disorder, and one or more UEMS disorder diagnosed.

We analysed the 1993 1994 factors associated with outcomes (neither symptom nor disorder in 1996 1997 vs. symptoms only and vs.

-disorders), using multinomial non-ordinal logistic regression. Factors were included in the model if they reached a level of 0.20 in P bivariate analyses. If some prognosis factors were too strongly correlated, only the most appropriate one was included.

Of the initial 700 workers, 598 were followed completely during the 3-year period (85.4 ). At baseline, 464 of them had UEMS presence of UEMS disorder diagnosed in 1993 1994, ), with a stronger association for disorders than for symptoms only.

-Table 1 This study is one of the first to consider jointly occupational, personal, and pain factors associated with prognosis of UEMS symptoms or disorders, in a worker population performing highly repetitive tasks. Despite several limitations (no information on events during the years between examination, losses to follow-up, subjective self-assessment of risk factors, definition of UEMS disorders based on clinical examination), these results were consistent with the few existing studies on prognosis: older age is known to be related with a poor prognosis. So are pain intensity and duration at baseline, , , and presence of disorders at baseline. ,

The role of In conclusion, we found that work with force was associated with a poorer prognosis, as were age and pain intensity at baseline.

%

  symptoms or disorders and were included in this analysis (77.6 of the 598 workers). Most had a disorder (n 421, prevalence 70.4 ), had symptoms in isolation. No difference in outcome was found between those who reported their job as changed in the last three years (n 114) and those who declared that it had not (n 350, >0.05). Factors associated with the three-year outcome in multivariate = = P analyses were age, work with force, and pain intensity (adjusted for gender, presence of psychosomatic of depressive problem and " "

  Further studies, however, are needed to clarify the role of personal and work-related factors in determining the prognosis of UEMS disorders in working populations. occupational cohort study STUDY DESIGN:

Ackowledgements:

We are grateful to the members of the Study Group on Repetitive Work who were involved in this survey, as well as to the occupational physicians who collected the data and made the physical examinations.

We thank Lawrence J Fine for his contribution to the preparation of the questionnaire in 1992.

Footnotes:

 [START_REF] Roquelaure | Active epidemiological surveillance of musculoskeletal disorders in a shoe factory[END_REF]3

Table 1

Multivariate analysis based on multinomial logistic model between the three-year outcome and the baseline variables (reference workers with no symptom and no UEMS disorders in 1996 1997) The multiple UEMS disorders and duration of pain highly associated with pain intensity, were not included in the model. * difference between the outcomes and the reference group (Wald Chi test).