Rebecca A Musgrave

Paul Choi

Robert L Harniman

Robert M Richardson

Chengshuo Shen

George R Whittell

Jeanne Crassous

Huibin Qiu

Ian Manners

R O Ro

Chiral Transmission to Cationic Polycobaltocenes over Multiple Length Scales Using Anionic Surfactants

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INTRODUCTION

High molar mass metallopolymers are of growing interest as a result of the combination of their functionality, arising from the presence of metal centers, and the facile processing characteristics of macromolecular materials. [1][2][3][4][5][6][7][8] Examples of metallopolymers that display redox activity have attracted considerable attention and have recently found application in electrocatalysis [9][10][11] and sensing, [12][13][14] and as responsive surfaces [15][16][17][18][19] and capsules. [20][21] Their utility as precursors to catalytic and magnetic nanoparticles has also been wellinvestigated. [22][23][24][25][26][27][28][29] However, although chiral organic polymers are well-developed and are of considerable current interest as functional materials with potential applications in chiral recognition, asymmetric catalysis and enantioselective discrimination, [30][31] analogous metallopolymers, which may display additional advantageous properties, are virtually unexplored. Rare examples of metal-containing chiral macromolecular materials include helical cobaltocenium oligomers (e.g. 1, Fig 1, with 2-6 repeat units), [32][33] low molecular weight nickel-containing helical ladder polymers based on salophen units (e.g. 2, Fig 1, number average degree of polymerization DPn ≤ 10), [34][35] and coordination polymers incorporating chiral ligands (e.g. 3, Fig. 1). [36][37] Transfer of chirality from molecules to nano-and macroscopic structures can be achieved by self-assembly, where molecular chirality is amplified on a larger length scale by cooperative non-covalent interactions, such as hydrogen bonding, π-π aromatic stacking, [38][39][40] ion-dipolar interactions, and electrostatic interactions. [40][41] Of relevance to this work are a series of organic achiral polymers, which have been shown to exhibit optical activity upon complexation with chiral guests. 30 These 'dynamic helical polymers' rely on non-covalent interactions with the chiral guest in order to induce helicity within the polymer structure. 30 Another fascinating recent report on metal-containing chiral assemblies involves the synthesis of organogelator nanoribbons and their templating of Au-nanocrystals to form double-helical Au nanowires. 42 Recently, our group reported the thermal ring-opening polymerization (ROP) of the strained dicarba [2]cobaltocenophane monomer (4) to yield high molecular weight neutral poly(cobaltocenylethylene) (PCE) with degree of polymerization n, which features neutral cobaltocene units in the main chain of the polymer (Fig. 2). Upon one-electron oxidation of the cobaltocene units, poly(cobaltoceniumethylene), [PCE][X]n (X = Cl -, NO3 -, -OTf ( -OTf = trifluoromethanesulfonate)), is formed (Fig. 2). [43][44] Unlike related ferrocene-containing polymer analogues such as polyferrocenylsilane (PFS) (Fig. 2), 45 in which the repeating unit features a stable 18 valence electron (VE) metallocene, the cobaltocene units in neutral PCE possess 19 VEs. Upon oxidation to the polycationic form, [PCE] n+ , which features 18 VE cobaltocenium units, the resulting polyelectrolyte is air-and moisture-stable with a variety of counter-anions. 43 The solubility of [PCE] n+ depends on the nature of these anions; for example, [PCE] [Cl]n and [PCE][NO3]n are water soluble, 43 while [PCE][OTf]n exhibits higher solubility in organic solvents, such as THF and MeOH. 46 Using this cobalt-containing polyelectrolyte, we have also recently reported the first example of a high molar mass 'chiral polymetallocene', which was synthesized via templating of the [PCE] n+ polyelectrolyte with deoxyribonucleic acid (DNA) of ca. 2000 base pairs in water (Fig. 2). 47 The resulting [PCE][DNA] complex apparently exhibits strong electrostatic interactions between the anionic phosphodiester groups on the DNA backbone and the cationic cobaltocenium units in the main chain of [PCE] n+ , which was found to have taken on a chiral conformation as a result of embedding in the minor or major groove of the DNA double helix. Unfortunately, the poor solubility of the DNA complexes in common solvents substantially limited further investigation and the applicability of these chiral materials. 'Ionic self-assembly', described as the cooperative assembly of charged surfactants and oppositely charged building blocks, is a well-established method for the creation of functional materials. [48][49][50] Of particular interest is the cooperative electrostatic surfactant binding to oppositely charged polyelectrolytes. [51][52] N-acyl-amino acid chiral anionic surfactants (which feature a tetrahedral chiral carbon center at a position adjacent to the anionic carboxylate functional group, Fig. 3) 53 have been intensively studied as building blocks for chiral liquid crystals, [54][55] and recently as templates for chiral mesoporous materials. [56][57] Herein, we report the formation of readily soluble chiral complexes of [PCE] n+ using these amino acid-derived chiral anionic surfactants as counter anions. We also demonstrate the self-assembly of these chiral complexes into structures on the micron lengthscale which display morphologies reflecting the chirality of the surfactant.

RESULTS AND DISCUSSION

Complexation of PCE with Chiral Surfactants

Facile anion exchange in side-chain cobaltoceniumcontaining metallopolymers has been demonstrated by Tang et al., 58 and has recently been utilized to synthesize polymer/antibiotic bioconjugates via ion-pairing of the carboxylate functional group of β-lactam antibiotics and pendent polymer cobaltocenium units. 59 Upon coulombic association of N-acyl-amino acid derived chiral anionic surfactants with cationic repeating units of [PCE] n+ , the proximity of the cobaltocenium units within the polymer main chain to the asymmetric center is expected to favour chiral transcription from the surfactant to the polymer.

With this in mind, we employed both enantiomers of two chiral surfactants: N-palmitoyl-L-alanine (C16-L-Ala) and N-palmitoyl-D-alanine (C16-D-Ala), and N-palmitoyl-Lphenylalanine (C16-L-Phe) and N-palmitoyl-Dphenylalanine (C16-D-Phe) (Fig. 3) in the chiral complexation of [PCE] n+ . Neutral PCE was prepared via the thermal ring-opening polymerization of dicarba [2]cobaltocenophane 4 (Scheme 1). 43 The synthesis of monomer 4 has been subject to recent improvements, resulting in substantially higher yields (37% vs ca. 10%, see experimental section). The [PCE][A*]n (A* represents a chiral anionic surfactant) complexes were subsequently synthesized by oxidation of neutral PCE with atmospheric oxygen in solutions of the respective chiral anionic surfactant as the sodium salt (ca. 2.0 eq. in a mixture of water, ethanol and THF) (Scheme 1). After vigorous stirring for 48 h, the mixture was filtered to remove any remaining solid and gel-like products, which were ascribed to crosslinked PCE formed during the thermal ROP process. 43 Dialysis of the resulting yellow solution was performed against deionized water and ethanol alternately (Fig. S1) to remove the excess surfactant, small molecule residues and any oligomeric [PCE] n+ derivatives. [PCE][A*]n complexes were obtained in ca. 40% yield after drying under vacuum. The 1 H NMR spectrum of [PCE][C16-L-Ala]n (shown in Fig. S2) indicates the complexation of cobaltocenium units to surfactant anions in a 1:1 ratio. The [PCE][A*]n complexes were found to be readily soluble in common organic solvents such as methanol, ethanol and THF, but insoluble in water (Fig. S1). This is indicative of a strong coulombic association between cationic cobaltocenium units of [PCE] n+ and the carboxylate moiety of the chiral surfactant anions, with effective shielding of the ion pairs by the aliphatic tails of the surfactants. We propose that the resulting structure of these complexes is similar to that of brush-like amphiphilic polymers, [60][61] but with the brush component (surfactant) linked to the polymer main chain by coulombic rather than covalent interactions. It was found that without removing the base (OH -) generated during the oxidation process, cleavage of the cobaltocenium units occurred, as has previously been reported. 62 This decomposition was observed to be more significant upon increasing the reaction concentration, or by replacement of the chiral surfactants with simple carboxylates, such as sodium acetate and sodium dodecanoate (SDS, Fig. 3).

N H NaO O O Me H 7 N H NaO O O H 7 N H NaO O O Me H [Na][ N -acetyl-L -alanine] [Na][C16 -L -Phe] Ph [Na][C16 -L -Ala]

Origin of Chirality in PCE Complexes

The chirality of the [PCE][A*]n complexes in ethanolic solution was studied by circular dichroism (CD) (Fig. 4).

[PCE][C16-L-Ala]n (Fig. 4a, red line) showed an intense negative CD response below 240 nm, which was assigned to absorption of the chiral [C16-L-Ala] -anions (Fig. S3). 63 In the absorption region of 250-300 nm, corresponding to the charge transfer band of cobaltocenium units within [PCE] n+ , 43,64 the CD response of the [PCE][C16-L-Ala]n complex showed a negative maximum and then positive maximum (Cotton effect) as the absorption wavelength decreased. The CD spectrum of the [PCE][C16-D-Ala]n complex exhibited an exact mirror-image to that of its L- enantiomer (Fig. 4a, blue line). The observation of equal but opposite split Cotton effects around 270 nm for the C16-D-Ala and C16-L-Ala complexes of [PCE] n+ indicates that the alanine-based asymmetric center within these surfactants transcribes chirality to the entire length of the metallopolymer, by imposing an asymmetric conformation on the ethylenic linker (Pfeiffer effect). [65][66][67] This affords the chiral space for a unique example of Exciton Coupling (EC) between the chromophoric [CoCp2] + units, where the electronic transition moments of these chromophores interact spatially so that the energy level of the excited states split. [68][69] EC is usually observed in axially chiral biarylic systems (such as 1,1′-bi-2-naphthols), in chiral vicinal diols substituted with identical chromophores, and in macromolecular complexes such as DNA-porphyrin conjugates. [START_REF] Harada | In Electronic CD Exciton Chirality Method: Principles and Applications[END_REF][START_REF] Telfer | [END_REF] Interestingly, together with the previously reported [PCE][DNA] complex (Fig. 2), these can be considered as novel combinations of Pfeiffer effects 69 and EC chromophores where the chirality of the DNA or the alanine-based surfactant is transferred to the whole metallopolymer. Variable temperature CD experiments on [PCE][C16-L-Ala]n in ethanol revealed that the chiral transfer (i.e. the magnitude of the CD response) from the surfactant to the metallopolymer increases as the temperature is lowered (Figs. S4 andS5). To further elucidate the origin of induced chirality of the [PCE][A*]n complexes, a number of monomeric cobaltocene derivatives were also subjected to oxidation in the presence of [C16-L-Ala] -and [C16-D-Ala] -. The complexes formed with bis(ethylcyclopentadienyl)cobalt(II) (5, Fig. 5) exhibited no Cotton effect over the absorption region of 250-300 nm (the charge transfer band of cobaltocenium) (Fig. S6a). Similarly, the complexes formed by the hydrocarbon-bridged [n]cobaltocenophanes ( [4][C16-L/D-Ala] and [6][C16-L/D-Ala], Fig. 5), in which the conformation of the hydrocarbon bridge is fixed, showed no evidence of induced chirality (Figs. S6b,c). This provides crucial evidence that the monomeric analogues are not chiral in this regard, and that sufficient polymer backbone length is required for chirality to be expressed. It therefore seems most likely that the induced chirality originates from the polymeric chain adopting a structure which features axially chiral ethylenic CH2-CH2 bridges (where the dihedral angle replicates the asymmetry along the polymer chain -see Fig. 6). To test this hypothesis, oligo(cobaltocenylethylene) with 5 repeating units, OCE5 (Fig. S7), 43 was synthesized and subjected to oxidation and complexation with the chiral anionic surfactants (Fig. 5).

Co Co [ 4 ][C16 -L -Ala] Co [ 6 ][C16 -L -Ala] [ 5 ][C16 -L -Ala] H Me O O O R NH H Me O O O R NH H Me O O O R NH R = (CH2)14 CH 3 Co 3 Co Co H Me O O O R NH H Me O O O R NH H Me O O O R NH [ OCE 5][C16 -L -Ala]5

The resulting [OCE5][A*]5 complexes exhibited CD spectra analogous to the [PCE][

A*]n complexes; i.e. featuring two sets of Cotton effects with opposite signs in the absorption band of [PCE] n+ , and mirror-image signals for the enantiomers (Fig. S8). However, the Cotton effects are of dramatically lower intensity when compared to the corresponding polymeric [PCE][A*]n complexes, again indicating a strong effect of the length of the polymer backbone. In contrast, the complexes formed by the shorttail N-acyl-amino acids, i.e.

, [PCE][N-acetyl-L-alanine]n and [PCE][N-acetyl-D-alanine

]n, revealed much weaker Cotton effects (Fig. 4c), presumably because the absence of a long alkyl side chain leads to insufficient twisting of the ethylenic C-C bonds. This indicates at least that the long tail of the chiral counter anions is important for the transcription of chirality. When even smaller surfactants (L-alanine and D-alanine sodium salts) were employed, decomposition of the material was evident during the oxidation process, probably due to the increase in basicity on employing primary amines, to which cobaltocenium ions are sensitive. 62 In these cases (L-alanine and Dalanine), no chirality was observed by CD (Fig. 4d). In contrast to former observations on the structure of [PCE][DNA] (Fig. 2), where it was postulated that main chain of [PCE] n+ adopted a helical conformation due to tight complexation with the DNA strand, here we propose that the axial conformation of each repeat unit (CH2-Cp-Co + -Cp-CH2) in the polymer backbone of [PCE][A*] facilitates the emergence of axial chirality. As a consequence of this axial chirality, an EC signature appears in the CD spectra. Indeed, bisignate (i.e. change of sign within the band) CD signatures, such as those observed for the [PCE][C16-D/L-Ala]n complexes at λ > 250 nm, occur where two or more strongly absorbing chromophores are located nearby in space within a chiral system. 4b). However, the intensity of the signals was slightly decreased in the [PCE] n+ absorption band region (Fig. 4b). According to the exciton coupling model, the EC response is sensitive to both the chiral CH2-CH2 dihedral angle and the interchromophoric distance, which defines the degree of chirality of the polymer backbone. It is therefore likely in the case of the phenylalaninecontaining complexes that the optical purity is the same as that for the alanine analogs, but the CD signal is just weaker on account of a larger dihedral angle between the Cp rings of each cobaltocenium unit that arise from the greater side-chain bulk (-CH2C6H5 vs. -CH3) and the close columbic association.

Self-assembly of Chiral PCE Complexes

In collaboration with Faul and coworkers we have recently reported the preparation of polyferrocenylsilane (PFS, see Fig. 2) polyelectrolyte-surfactant complexes and their ionic self-assembly into a rich variety of morphologies in bulk and thin films. [72][73][74][75] In these systems, the PFS polymer backbone was functionalized with pendent ammonium groups, which subsequently interacted coulombically with anionic sulfonate surfactants. Compared to the PFS polyelectrolytesurfactant complexes, the [PCE][A*]n complexes exhibit a number of unique features: (i) the surfactant counter anions are chiral, (ii) the charges of the polyelectrolyte are located at the metallocene repeat unit and thus are embedded in the polymer backbone, and (iii) the coulombic pairing is in this case between metallocenium cations and carboxylate anions. With these distinct features, the [PCE][A*]n complexes were expected to exhibit interesting behaviour upon self-assembly. A variety of imaging techniques were employed to characterise the structure of the [PCE][C16-L-Ala]n in various solvents, including its self-assembly behaviour. Transmission electron microscopy (TEM) of drop-cast ethanolic solutions of [PCE][C16-L-Ala]n (ca. 12 mg mL -1 ) revealed the presence of both film and fibrous material (with average width of ca. 6 nm) with the latter protruding from the edges of the former (Figs. 7a and7b). The protrusion of these long fibrils from areas of the TEM grid that are covered by polymer film suggests that fiber formation might be the result of a drying effect. Energydispersive X-ray (EDX) spectroscopy was employed to confirm the presence of cobalt within the film, the fibrils, and even areas of the grid where no material could be visibly identified (see Fig. 7b and Fig. S9 for details). This suggests that the grid is covered in a thin film of [PCE][C16- L-Ala]n which is concentrated into thicker areas of film and fibers upon drying, and only the latter two are of sufficient contrast to be observed by TEM.

Dynamic light scattering (DLS) experiments were performed on an ethanolic solution of [PCE][C16-L-Ala]n (ca. 12 mg mL -1 ). The size distribution by volume as determined by DLS gives a population of hydrodynamic radius (Rh) 1.2 nm (Figs. S10 andS11), which is small relative to that expected for [PCE] n+ macromolecules. 43 The pseudo-brush polymers afforded by complexation, however, are expected to deviate in shape from the spherical particles for which the diffusion was modelled. The size distribution by intensity (Fig. S12) indicates the presence of a species of Rh = 12.2 nm, which would seem more consistent with the [PCE] n+ macromolecular species (see Figs. S13 andS14). [START_REF]PCE][Cl]n in water indicated Rh = ca. 18 nm (from the size distribution by volume), corresponding to a weight-average molecular weight of ca. 19,000 g mol -1 for sodium polystyrene sulfonate[END_REF][START_REF]DLS experiments were performed on both aqueous and ethanolic solutions of[END_REF] Regardless, this DLS data affords no evidence to support the existence of multimicron fibers in ethanol solution, which were observed in the dry-state by TEM (Figs. 7a,b).

The association of the polymer and surfactant in solution was analyzed by diffusion ordered spectroscopy (DOSY) NMR (Fig. S15). The [PCE][C16-L-Ala]n complex is fully soluble in d4-methanol, 58 and the diffusion coefficient of [PCE] n+ (1.2 × 10 -10 m 2 s -1 ) is significantly smaller than that of the [C16-L-Ala] -anions (3.4 × 10 -10 m 2 s -1 ) in this solvent. This indicates that although coulombic interactions between the polyelectrolyte and the surfactant anions are clearly present (resulting in the transfer of chirality as observed by CD spectroscopy), the anions are not tightly bound to [PCE] n+ when solvated in polar organic solvents. Such ion association has been previously described for cobaltocenium-containing polyelectrolytes, 58 and supports the DLS data, indicating that fibrous structures are not present in ethanol solution.

In order to probe the crystallinity of the ethanolsoluble complex, wide angle X-ray scattering (WAXS) analysis of [PCE][C16-L-Ala]n drop cast from ethanol solution was performed. The presence of sharp reflections at 2.8, 3.1, 3.4, 3.8, 4.0, 4.1, 10.2 and 15.2 Å, suggests that the material does indeed exhibit crystalline order (Fig. S16). The structure of the fibers is, at present, unclear, but it is possible that interdigitation of the hydrocarbon tails of the surfactant molecules occurs as the local concentration of the solution increases upon drying.

Small angle X-ray scattering (SAXS) was also performed on ethanolic solutions of [PCE][C16-L-Ala]n (four samples were prepared at 18, 22.5, 33 and 45 mg mL -1 -see Figs. S17-20), where the scattered intensity (I) observed for these samples in the range of 0.1<Q<0.6 reflects the simple change in solvent structure on changing the concentration of the suspended particles (Fig. S17). The slope of the loglog plot of intensity (I) vs. scattering vector (Q) in this range (-1) is indicative of thin rods (Fig. S18), although the samples were not sufficiently dilute to result in single particle scattering (Fig. S19).

Differential scanning calorimetry (DSC) was employed to further elucidate the crystalline nature of the [PCE][C16-L-Ala]n complex (again drop cast from ethanol solution). Cyclic temperature DSC experiments were performed between -30 °C and 60 °C, as thermal gravimetric analysis (TGA) revealed the onset of decomposition of the material above 60 °C (Fig. S21). These cyclic DSC scans consistently revealed two first-order endothermic processes during the heating phase at ca. 16 °C and 40 °C, followed by two exothermic processes during the cooling phase at ca. 20 °C and -4 °C (Fig. S22). The thermal behavior of the chiral surfactant-paired polymer is significantly different to that of the related chloride-paired [PCE] [Cl]n polymer and the Na[C16-L-Ala] salt. DSC experiments on [PCE] [Cl]n revealed only a very small second-order transition at ca. 97 °C (Fig. S23), which may be assignable to the Tg (glass transition) of the polymer. Despite the absence of a Tm (melt transition) in the thermogram, WAXS analysis of [PCE] [Cl]n showed some crystalline order, with one broad reflection corresponding to a d-spacing of 4.1 Å (Fig. S24). Unfortunately, attempts to anneal the sample in order to increase its crystallinity (by either thermal annealing at 120 °C, or solvent annealing with EtOH) were unsuccessful. Some structural similarity between the chloride-and surfactant-paired polymers can be drawn, as the broad reflection at 4.1 Å also appears to feature prominently in the WAXS pattern of the [PCE][C16-L-Ala]n complex (Fig. S16). The origin of this reflection, however, remains unclear.

Additional investigation into the thermal behavior of the Na[C16-L-Ala] salt was conducted by DSC measurements (Fig. S25), revealing a second-order transition at ca. 38 °C (perhaps assignable to a Tg associated with the C16 surfactant chains), and a first-order melt transition at ca. 57 °C (with the reverse processes present in the cooling scan). The WAXS data for this surfactant is displayed in Fig. S26.

After dialysis of a diluted ethanolic solution of [PCE][C16-L-Ala]n (four times diluted; ca. 3 mg mL -1 ) against THF, and subsequently deionized water, for 16 h, the complex precipitated from solution, forming a fine pale yellow suspension. [START_REF]although it was found that dialysis first from ethanol into THF and then into water produced more well-defined consistent helices[END_REF] TEM imaging of dried samples of this suspended material showed the presence of twisted helical structures. The material appears to be composed of a mixture of tightly twisted helices (Fig. 7c,d) and in some cases, larger twisted coils of various sizes (Fig. S27), which assemble into even larger aggregates which are difficult to image via TEM, as a result of their large size and high electron density. The presence of cobalt within these helical structures was confirmed by EDX spectroscopy (see experimental section, Fig. S28). Furthermore, control experiments showed that these regular helical self-assembled structures were inaccessible when using the analogous achiral PCE/surfactant complex formed by [PCE] n+ and sodium dodecylsulfate (SDS) (Fig. S30) or an achiral long alkyl-grafted neutral PFS species (Fig. S31). This indicates that the presence of asymmetric centres within the surfactant anions is essential for defined chiral self-assembly. Solid-state CD measurements were performed on a dry sample of the [PCE][C16-L-Ala]n helical self-assembly product (see Fig. S32). The UV response of the material again features an absorption band at 250-300 nm, in the region consistent with cobaltocenium charge transfer in [PCE] n+ (Fig. 8b). 43 The CD spectrum of the assembled product exhibits a broad Cotton effect with a negative maximum (multiple features from ca. 400 nm) and subsequently a positive maximum as the absorption wavelength decreased to ca. 250 nm (Fig. 8b). This new CD signature may correspond to another expression of chirality; i.e. the supramolecular organization between each helical polymeric strand (tertiary structure), while the former EC signature of [PCE][C16-L-Ala]n in ethanolic solution (Fig. 8a) described the secondary structure of the brush-like polymer complex. Another feasible explanation for this change in CD response involves the difference in folding of the polymer chains in ethanol vs. water. It should be noted that the sign of the Cotton effect is the same (i.e. a negative CD maximum followed by positive CD maximum upon decreasing wavelength) for both the ethanolic solubilized [PCE][C16-L-Ala]n complex (Fig. 8a) and its aqueous self-assembly product (Fig. 8b), indicating that the handedness of these helical assemblies is inherited from the substituent polymer complex. WAXS analysis of a dry sample of the aqueous [PCE][C16-L-Ala]n assemblies was performed, indicating a largely amorphous material with weak reflections identified at 4.1 and 3.9 Å (Fig. S33). Again, the first reflection (4.1 Å) also features prominently in the WAXS pattern of the [PCE] [Cl]n complex (Fig. S24).

Although the structures formed by self-assembly in water can be clearly identified as helical, it is difficult to determine the "handedness" (direction of twist) of the helices solely by analysis of the TEM images, which only provide a two-dimensional perspective. Scanning electron microscopy (SEM) and field emission SEM (FE-SEM) was employed after sputter coating of the TEM grids with Pt/Pd alloy, to visualize the superhelices in three dimensions. It is evident from SEM images of individual helices which are many microns in length (e.g. Fig. 9a) that a left-handed twist is present within the helices formed by the [PCE][C16-L-Ala]n complex. In addition, all other helices which were identifiable by SEM could also be assigned as left-handed, indicating that enantiomeric purity of the molecular surfactant anion was being transferred not only to the macromolecular complexes, but also to structures on a much larger length scale. Fig. 9b shows a collection of these helices at the edge of a large section of aggregated material, as well as a larger coil (exhibiting both increased pitch length and diameter). Additional representative SEM and FE-SEM images (see Supporting Information, Figs. S34 andS35) show areas of aggregation in which twisted material has assembled en masse to form much larger structures. The precipitation of material from solution upon dialysis with water is thought to be driven by association of the hydrophobic hydrocarbon surfactant tail ends which surround the metallopolymer chain. Although the organization of [PCE][C16-L-Ala]n chains within these helical structures is not yet fully understood, it is likely that the polymer chains align side by side, and the axial chirality of each chain translates to a further axial chirality, or helicity, of the resulting assembly (Fig. 9c). The left-handed twist of the [PCE][C16-L-Ala]n helices was also confirmed by Atomic Force Microscopy (AFM). Imaging was performed on samples drop cast onto both mica (Figs. 9d,e) and carboncoated copper grids (Figs. 9f,g). The three-dimensional height profile shown in Fig. 9e

SUMMARY

We have demonstrated the formation of soluble chiral [PCE] n+ complexes through the ion-pairing of a polyelectrolytic metallopolymer with chiral surfactant counter anions during oxidation, and the solution selfassembly of [PCE][C16-L-Ala]n into helical structures which reflect the molecular chirality of the complex. The novel transcription of chirality, where the surfactant chirality induces an exciton coupling response which is dependent on the ethylenic dihedral angle and the intercobaltocenium distance in the [PCE] n+ backbone, inspires a new strategy to prepare chiral macromolecular systems. The versatile self-assembly in different solvents to form hierarchical superhelical structures also implies a wide range of potential applications of these complexes as chiral materials. Future work will focus on theoretical calculations to verify the exciton coupling model of chirality with these complexes, the development of controlled self-assembly methods to reduce aggregation in aqueous solution, and the synthesis and hierarchical selfassembly of chiral complexes derived from PCE block copolymers. 46

EXPERIMENTAL SECTION

L-alanine, D-alanine, N-acetyl-L-alanine, N-acetyl-Dalanine, sodium acetate, sodium decanoate, bis(ethylcyclopentadienyl)cobalt(II), and sodium dodecylsulfate (SDS) (all purchased from Sigma-Aldrich) and CoCl2 (purchased from Strem Chemicals) were used without further purification. The fly trap ligand Li2[(C5H4)2(CH2)2], [START_REF] Collins | [END_REF] tricarba [3]cobaltocenophane, 44 (PCE) 43 , [PCE][Cl]n 43 and [PCE][NO3]n 43 were prepared according to literature procedures. CoCl2•dme was prepared by refluxing CoCl2 in neat dimethoxyethane. Dicarba [2]cobaltocenophane was prepared according to a modified synthesis (see below). C16-L-Ala, C16-D-Ala, C16-L-Phe and C16-D-Phe were synthesized according to a literature procedure. 53 L-alanine, D-alanine, N-acetyl-Lalanine, N-acetyl-D-alanine, C16-L-Ala, C16-D-Ala, C16-L-Phe and C16-D-Phe were transformed to their sodium salts by reaction with one equivalent of sodium hydroxide in aqueous solution (0.1 mol L -1 ). Dodecyl-grafted PFS (PFS-C12) was prepared according to a literature procedure. 80 Dialysis was performed using Spectra/Por ® molecularporous membrane tubing (MWCO 8000 g mol -1 ), into which solutions were transferred and sealed with dialysis clips. Dialysis against any particular solvent was performed for >6 hours.

All syntheses and manipulations of neutral cobaltocene-containing compounds were carried out under an inert atmosphere of dinitrogen or argon using standard Schlenk line of glovebox techniques (MBraun glovebox MB150G-B maintained at < 0.1 ppm H2O and < 0.1 ppm O2. Dry THF was distilled under dinitrogen from Na/benzophenone immediately prior to use. Dry hexanes was obtained from a Grubbs-type solvent system employing alumina and supported copper columns. 81 1,2-Dimethoxyethane was dried over CaH2 and distilled before use.

Photoirradiation experiments were carried out using Pyrex-glass-filtered emission (λ > 310 nm) from a 125 W high pressure Hg vapour lamp (Photochemical Reactors Ltd.).

1 H NMR spectra were recorded at ambient temperature on a JEOL ECS NMR 300 MHz spectrometer or Varian NMR 500 MHz spectrometer, reported relative to external tetramethylsilane, and referenced to the most downfield residual solvent resonance (CD3OD: δH 3.31 ppm). Diffusion ordered spectroscopy (DOSY) NMR experiments were carried out on a Varian NMR 500 MHz spectrometer. The diffusion delay set to 80 ms, and DOSY NMR spectra were processed with DOSYToolbox. 82 Circular dichroism (CD) spectra were obtained using a JASCO J-815 spectrophotometer. Solution samples were prepared in 1 mm path-length quartz cuvettes, and solid samples (ca. 5 mg) were placed between two quartz plates. Measurements were performed at room temperature (ca. 25 °C) under constant nitrogen flow, which was used to purge the ozone generated by the light source of the instrument. Three scans were averaged per spectrum to improve the signal-to-noise ratio, operating from 200 to 500 nm at a scan rate of 100 nm min -1 and a bandwidth of 1 nm.

UV-vis spectra were obtained on a Thermo Scientific NanoDrop 2000c UV-vis spectrophotometer, operating from 200 to 500 nm at a scan rate of 100 nm min -1 . Differential scanning calorimetry (DSC) was performed on a TA Instruments Q100 calorimeter at a scan rate of 10 °C min -1 under a 50 mL min -1 flow of prepurified nitrogen. Samples were placed in hermetic aluminium pans and weighed using a XT220A Precisa microbalance. TGA was measured on a Thermal Advantage TGAQ500 at 10 °C min -1 under N2. DSC and TGA scans were analysed using the TA Instruments software Universal Analysis 2000 version 4.5a build 4.5.0.5.

Transmission electron microscopy (TEM) images were obtained on a JEOL1200EX II microscope operating at 120 kV and equipped with an SIS MegaViewIII digital camera. Samples were prepared by placing one drop (ca. 10 µL) of solution on a carbon-coated copper grid (Agar Scientific, square 600 mesh), which was placed on a piece of filter paper to remove excess solvent. No staining of the samples was necessary. Energy dispersive X-ray (EDX) spectroscopy was performed using an Aztec X-Max 80 mm 2 silicon drift detector (Oxford Instruments) attached to a JEOL2100F field emission scanning transmission electron microscope (Chemistry Imaging Facility at University of Bristol).

Atomic force microscopy analyses were performed under ambient conditions using a Bruker Multimode VIII atomic force microscope equipped with a ScanAsyst-HR fast scanning module and a ScanAsyst-Air-HR probe (tip radius, 2 nm), utilizing peak force feedback control. Samples were drop-cast onto either carbon-coated copper TEM grids or freshly cleaved mica surfaces (Ruby muscovite sheets, 100 mm x 20 mm x 0.15 mm, Agar Scientific). Images were recorded after drying the sample under ambient conditions and processed using Bruker Nanoscope Analysis software.

Scanning Electron Microscopy was performed using a JEOL JSM 6330F Field Emission Scanning Electron Microscope or a JEOL JSM 5600LV Scanning Electron Microscope. Samples were drop cast onto carbon-coated copper grids and subsequently sputter-coated with platinum/palladium alloy.

Dynamic Light Scattering (DLS) experiments were performed to determine hydrodynamic radii of polymeric species. Samples (2 mL) of different polymer solutions ([PCE][C16-L-Ala]n: 12 mg mL -1 , EtOH; [PCE] [Cl]n: 2 mg mL - 1 , H2O) were placed into optical glass cuvettes (10.0 mm path length). The measurements were performed on a Malvern Instruments Zetasizer Nano S using a 5 mW He-Ne laser (633 nm) at 25 °C. The correlation function was acquired in real time and analyzed with a function capable of modelling multiple exponentials. This process enabled the diffusion coefficients for the component particles to be extracted, and these were subsequently expressed as effective hydrodynamic radius, by volume and intensity, using the Stokes-Einstein relationship.

Wide angle X-ray scattering (WAXS) experiments were carried out on a D8 Advance diffractometer fitted with an 0.6 mm fixed divergence slit, knife-edge collimator and a LynxEye area detector using Cu Kα radiation (λ = 1.5418 Å). Data was collected between 5 and 50 degrees 2θ in θ/2θ mode with a step width of 0.5°. Samples were prepared by the loading of solid samples (or by dropcasting of samples in solution) onto a silicon wafer prior to analysis.

The solution X-ray diffraction data was taken using a Ganesha small angle X-ray scattering apparatus (SAXSLAB, Denmark). The instrument uses copper Kα radiation (1.5 Å) and the scattering pattern is detected on a 2-dimensional Pilatus 300K X-Ray Detector (Dectris, Switzerland). Prior to measurement, the absolute intensity scale was calibrated using a sample of ethanol. Samples were prepared at known concentrations in ethanol and sealed into 1.5 mm diameter quartz capillary tubes (Capillary Tube Supplies, Cornwall, UK) with epoxy resin. The thickness of each capillary was measured exactly by scanning the X-ray beam across the sample and observing the full-width at half-maximum of the transmitted intensity using a pin diode. All samples were then measured at two sample to detector distances (1400 mm and 350 mm) and measurements of the corresponding empty capillary and solvent background were subtracted prior to fitting. The instrument was evacuated during measurements to reduce air scattering.

Modified synthesis of dicarba[2]cobaltocenophane (4): CoCl2•dme (1.42 g, 6.47 mmol) and the "fly-trap" ligand Li2[(C5H4)2(CH2)2] (1.0 g, 5.88 mmol) were separately dissolved in dry THF (2 x 125 mL), and both suspensions were cooled to -78 °C with constant stirring. The ligand/THF suspension was added rapidly via cannula to the CoCl2•dme suspension, and the reaction mixture was stirred and allowed to warm to room temperature over a period of 16 h. The solvent was removed under reduced pressure and the residue was extracted with n-hexanes to give a dark red/purple solution, which was filtered through Celite (1" × 4") to remove LiCl. All volatiles were removed under reduced pressure and the resulting dark purple solid was purified by sublimation (40 °C/-78 °C, 5.0 × 10 -2 mbar) to afford the product (4) in 37% yield. This compares to a yield of ca. 10% via the previously reported procedure. 44

Synthesis of [PCE][A*]n:

In a 30 mL glass vial, PCE (14 mg, 0.093 mmol of cobaltocene units) was combined with an aqueous solution of Na[A*] (1.4 mL, 0.1 mol L -1 , ca. 2 eq.) (A* = C16-L-Ala, C16-D-Ala, C16-L-Phe, C16-D-Phe, N-acetyl-Lalanine, N-acetyl-D-alanine, L-alanine, D-alanine, sodium acetate, sodium decanoate or SDS). To aid the dissolution of PCE and the resulting products, ethanol (10 mL) and THF (5 mL) were also added. The mixtures were stirred in the presence of atmospheric oxygen for 48 h, during which time the black PCE was gradually consumed, yielding a yellow suspension. Ethanol (10 mL) was subsequently added and the suspension was filtered to remove the remaining solid material and gel-like products (likely to be crosslinked PCE formed during thermal ROP). The clear yellow filtrates were transferred into a dialysis bag (MWCO 8000 g mol -1 ) and subjected to dialysis against alternating deionized water and ethanol to remove excess surfactant, NaOH generated during oxidation, and [PCE] n+ oligomer derivatives. Without prompt dialysis against water and ethanol after the initial complexation/oxidation, the yellow filtrates were unstable and decomposed resulting in dark brown solutions. Decomposition is attributable to reaction of the cobaltocenium units with NaOH generated during the oxidation process (2H2O + O2 + 4e - 4OH -), as has been previously described. 62 The resulting yellow solutions were concentrated by evaporation of solvents under a flow of N2 gas and subsequently dried under vacuum at room temperature (ca. 40% yield). Oxidation of monomeric cobaltocene derivatives: In a typical procedure, to a vial containing monomeric cobaltocene derivative (ca. 0.1 mml): bis(ethylcyclopentadienyl)cobalt(II) or the respective carba[n]cobaltocenophane (n = 2, 3), was added an aqueous solution of respective chiral anionic surfactant Na[C16-L-Ala] or Na[C16-D-Ala] (2 mL, 0.1 mol L -1 , ca. 2 eq. excess). To increase the solubility of the monomeric cobaltocene derivative and the resultant products, ethanol (5 mL) and THF (5 mL) were also added to each vial. The mixtures were stirred vigorously in the presence of atmospheric oxygen for 24 h, and the solutions were then directly subject to CD spectroscopy (see Fig. S6).

Synthesis of [OCE5][A*]5:

According to a reported procedure, 43 to a solution of dicarba [2]cobaltocenophane (100 mg, 0.464 mmol) in THF (dried and distilled, 2.0 mL) was added 12 mg of Li( t BuC5H4) (0.093 mmol, 0.2 eq.). The deep red solution was stirred at room temperature and irradiated with Pyrex-filtered UV light for 16 h, during which time a purple-brown suspension formed. The reaction was then quenched with degassed methanol (1.0 mL).

To determine the degree of polymerization (DPn) of the neutral OCE, a 0.60 mL aliquot of the above suspension was added to a solution of ammonium triflate (NH4OTf in 1:1 ethanol/water: 1 mL, 0.1 mol L -1 , ca. 1 eq.) and ethanol (5 mL) was added. The mixture was stirred vigorously in the presence of atmospheric oxygen for 24 h. After filtration, the solution was concentrated and dried under vacuum at room temperature. Integration of the corresponding peaks in the 1 H NMR spectrum (see Fig. S7) indicated that the resultant OCE had an average DPn of 5.

To prepare the oligomeric chiral surfactant/PCE complexes, similarly a 0.60 mL aliquot of the OCE5 suspension was added to an aqueous solution of Na[C16-L-Ala], Na[C16-D-Ala], Na[C16-L-Phe] or Na[C16-D-Phe] (1 mL of 0.1 mol L -1 , ca. 1 eq.). Ethanol (5 mL) was then added to aid the dissolution of the resulting products and the mixture was stirred in the presence of atmospheric oxygen for 24 h. After filtration, the solution was concentrated and then added drop-wise to 5 mL of rapidly stirred deionized water. The yellowish precipitate was isolated by centrifugation and dried under vacuum at room temperature. The products were redissolved in ethanol for further characterization by CD spectroscopy.

Self-assembly of [PCE][C16-L-Ala]n:

An ethanolic solution of [PCE][C16-L-Ala]n (1 mL, ca. 3 mg mL -1 ) was transferred into a dialysis bag (MWCO 8000 g mol -1 ) and subjected to dialysis twice against THF (30 mL x 2), after which the material remained in solution, and twice against deionized water (30 mL x 2), after which a fine pale yellow precipitate was observed.

EDX analysis of aqueous [PCE][C16-L-Ala]n assemblies: Cobalt was detectable by spot EDX analysis on a carbon-coated copper TEM grid at positions A and B (Fig. 7d), corresponding to tightly-wound helices of high contrast to the grid (see Fig. S28). Spot C overlays an area of the TEM grid at the edge of another helical structure, although in this case the helix is more "relaxed" (the pitch length is greater than for those investigated by spots A and B), which may be an inherent property of this particular helix, or a result of adhesion to the surface of the carboncoated grid upon drying (Fig. 7d). The presence of cobalt at this point could not be confirmed by EDX analysis (the net count was below the detection limit of the instrument), which may be a result of Spot C not entirely overlaying the helix, and also the relaxed nature of the helix, where the concentration of cobalt is expected to be lower than that covered by spots A and B (also evident from the lower contrast relative to the grid). Cobalt was also undetectable in spot D, which represents an area of the grid not populated by any helices. Here, the precipitation of [PCE][C16-L-Ala]n from aqueous solution upon selfassembly results in an absence of the film which was detected via drop casting of an ethanolic solution of the product.

Figure 1 .

 1 Figure 1. Metal-containing chiral oligomers and coordination polymers 1-3.

Figure 2 .

 2 Figure 2. Structures of dicarba[2]cobaltocenophane 4, poly(cobaltocenylethylene) (PCE), poly(cobaltoceniumethylene) ([PCE][X]n), polyferrocenylsilane (PFS) and [PCE][DNA] bioconjugate.

5 Figure 3 .

 53 Figure 3. Sodium salts of anionic N-acyl-amino acid chiral surfactants, N-acetyl-alanine and alanine (L-enantiomers), and sodium dodecyl sulphate.

Figure 4 .

 4 Figure 4. CD and UV-vis spectra of complexes formed by [PCE] n+ with (a) [C16-L-Ala] -and [C16-D-Ala] -, (b) [C16-L-Phe] - and [C16-D-Phe] -, (c) [N-acetyl-L-alanine] -and [N-acetyl-Dalanine] -, and (d) [L-alanine] -and [D-alanine] -, all at 0.5 mg mL -1 in EtOH.

Figure 5 .

 5 Figure 5. Complexes of monomeric cobaltocene derivatives 4, 5 and 6 with [C16-L-Ala] -, and molecular structure of oligomeric [OCE5][C16-L-Ala]5.

Figure 6 .

 6 Figure 6. Structure of [PCE][C16-L-Ala]n with example Newman projection along the CH2-CH2 axis to demonstrate chirality of the polymer backbone. Finally, the [PCE][C16-L-Phe]n and [PCE][C16-D-Phe]n complexes revealed similar CD spectra as the C16-L/D-Ala analogues (Fig.4b). However, the intensity of the signals was slightly decreased in the [PCE] n+ absorption band region (Fig.4b). According to the exciton coupling model, the EC response is sensitive to both the chiral CH2-CH2 dihedral angle and the interchromophoric distance, which defines the degree of chirality of the polymer backbone. It is therefore likely in the case of the phenylalaninecontaining complexes that the optical purity is the same as that for the alanine analogs, but the CD signal is just weaker on account of a larger dihedral angle between the Cp rings of each cobaltocenium unit that arise from the greater side-chain bulk (-CH2C6H5 vs. -CH3) and the close columbic association.Self-assembly of Chiral PCE ComplexesIn collaboration with Faul and coworkers we have recently reported the preparation of polyferrocenylsilane (PFS, see Fig.2) polyelectrolyte-surfactant complexes and

Figure 7 .

 7 Figure 7. TEM images obtained after drop-casting an aliquot of solutions of [PCE][C16-L-Ala]n complex in a) ethanol (ca. 12 mg mL -1 ) and b) spot EDX analyses of film and fibrous material (drop cast from 12 mg mL -1 ethanolic solution), or c) by drop-casting suspensions of [PCE][C16-L-Ala]n assemblies in water, and d) spot EDX analyses of helices. For detailed EDX analysis of spots see Supporting Information (Figs. S9 and S28).

Figure 8 .

 8 Figure 8. a) Solution state CD and UV-vis spectra of [PCE][C16-L-Ala]n at 0.5 mg mL -1 in EtOH, and b) solid state CD and UVvis spectra of the [PCE][C16-L-Ala]n self-assembly product formed in water. It should be noted that these helical morphologies are distinctly different to those formed by the achiral complex [PCE][NO3]n or the Na[C16-L-Ala] surfactant salt alone (Fig. S29a,b respectively), and thus indicate a key influence of chiral complexation on the self-assembly behavior.Furthermore, control experiments showed that these regular helical self-assembled structures were inaccessible when using the analogous achiral PCE/surfactant complex formed by [PCE] n+ and sodium dodecylsulfate (SDS) (Fig.S30) or an achiral long alkyl-grafted neutral PFS species (Fig.S31). This indicates that the presence of asymmetric centres within the surfactant anions is essential for defined chiral self-assembly. Solid-state CD measurements were performed on a dry sample of the [PCE][C16-L-Ala]n helical self-assembly product (see Fig.S32). The UV response of the material again features an absorption band at 250-300 nm, in the region consistent with cobaltocenium charge transfer in [PCE] n+ (Fig.8b).43 The CD spectrum of the assembled product exhibits a broad Cotton effect with a

Figure 9 .

 9 Figure 9. a-b) SEM images obtained after drop-casting an aliquot of suspensions of [PCE][C16-L-Ala]n in water on a carbon-coated copper grid and subsequent sputter-coating with Pt/Pd alloy: a) SEM image of an individual helix exhibiting a left-handed twist, b) FE-SEM image of helices and larger coil (lighter sections in image are associated with copper areas of the TEM grid). c) Postulated interdigitation of fatty acid brushes of individual polymer helices to form larger helical assemblies. d-g) AFM height images obtained by drop-casting an aliquot of suspensions of [PCE][C16-L-Ala]n in water onto: d) freshly cleaved mica (3D view of AFM image shown in e) with 5x exaggeration of Z-ratio for clarity) showing individual helices with some aggregation, and f), a carboncoated copper grid (3D view of AFM height images shown in g), with 5x exaggeration of Z-ratio for clarity) showing aggregation of helical material.

  clearly shows the lefthanded twist of each helix. Figs. 9f and 9g again demonstrate the aggregation of individual helices to form larger networks (additional representative AFM height images of helices and their aggregates are shown in Figs. S36 and S37).

  [PCE][C16-L-Ala]n 1 H NMR (CD3OD, 500 MHz): δ (ppm) 0.90 (t, 3H, [C16-L-Ala], -(CH2)14CH3), 1.29 (br m, 24 H, [C16-L-Ala], (CH2)12CH3), 1.60 (br m, 2 H, [C16-L-Ala], CH2(CH2)12CH3), 2.22 (br m, 2 H, [C16-L-Ala], CH2CH2(CH2)12CH3), 2.75 (br s, 4H, [PCE], (C5H4)(CH2)2), 5.65 (br s, 8H, [PCE], Co(C5H4)2).

PCE][A*] [PCE][A*]n n n n Co Co PCE PCE

	Scheme	1.	Synthesis	and	thermal		ring-opening
	polymerization of dicarba[2]cobaltocenophane 4, followed by
	oxidation in the presence of chiral anionic surfactants to yield
	[PCE][A*]n complexes.
			CoCl CoCl2 2 . .dme dme (1.1 (1.1 eq.) eq.)	Li Li	Li Li
	Co Co		THF THF -� 78 78 °C °C
			--2 2 LiCl LiCl
	4 4 (37% (37% yield) yield)
	140 140 °C °C		dme dme = = dimethoxyethane dimethoxyethane	R R = = Me, Me, CH CH2 2 Ph Ph R R ′ � = = (CH (CH2 2) )14 14 CH CH3 3
	1 1 h h
			Chiral anionic anionic surfactant surfactant salt salt ([Na][A*]) ([Na][A*]) H H2 2 O/EtOH/THF, O/EtOH/THF, O O2 2 , , 24 24 h h [Chiral	Co Co	O O O O	n n R R HN HN	H H R R ′ ′ O O

2 + +

ACKNOWLEDGMENT

The authors wish to thank Dr. Sladjana Baljak for preliminary experiments, Prof. Charl Faul for helpful discussions, and Dr. Sean Davis and Jonathan Jones in the Chemistry Imaging Facility at the University of Bristol (UoB) with equipment funded by UoB and EPSRC (EP/K035746/1 and EP/M028216/1). R.A.M. and I.M. thank the EPSRC for funding (EP/N030702/1). H.Q. thanks the National Natural Science Foundation of China (21674062, U1632117, 21704063), the Science and Technology Commission of Shanghai Municipality (16ZR1422600, 16PJ1406600, 17JC1400700), Shanghai Education Development Foundation and Shanghai Municipal Education Commission (16SG54) for financial support.

ASSOCIATED CONTENT

Supporting Information. CD and NMR spectra, WAXS and DLS data, DSC and TGA scans, TEM, SEM and AFM images, and EDX analysis. This material is available free of charge on the ACS Publications website at DOI: xxxxxxxxxx.

AUTHOR INFORMATION Corresponding Authors

1, *ian.manners@bristol.ac.uk 3, *hbqiu@sjtu.edu.cn

Author Contributions

All authors have given approval to the final version of the manuscript.

Notes

The authors declare no competing financial interest.


Lucas Freton
email: lucas.freton@gmail.com

Lauranne Tondut

Isabelle Enderle

Juliette Hascoet

Andrea Manunta

Benoit Peyronnet

PEYRONNET ; Benoit

Comparison of adjustable continence therapy periurethral balloons and artificial urinary sphincter in female patients with stress urinary incontinence due to intrinsic sphincter deficiency

Keywords: artificial urinary sphincter, urinary incontinence, sphincter deficiency, surgery Brief

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Stress urinary incontinence due to intrinsic sphincter deficiency is usually defined as the combination of a low urethral closure pressure, loss of urethral mobility, and a negative Marshall/Bonney test (urine leakage on straining or coughing not corrected by urethral support) [1; 2]. In daily practice, this condition is usually seen in two different populations: female patients who failed previous anti-incontinence surgical procedures (recurrent or persistent urinary incontinence after midurethral sling, Burch colposuspension,….) [START_REF] Lo | Risk Factors for Failure of Repeat Midurethral Sling Surgery for Recurrent or Persistent Stress Urinary Incontinence[END_REF] or patients with neurogenic stress urinary incontinence (usually due to spinal cord injury or spina bifida) [START_REF] Chartier-Kastler | Artificial Urinary Sphincter (AMS 800) Implantation for Women with Intrinsic Sphincter Deficiency: A Technique for Insiders?[END_REF]. The management of these women remains highly controversial, fascial slings and bulking agents being the most commonly used treatment option in North America [START_REF] Nadeau | Management of Recurrent Stress Incontinence Following a Sling[END_REF], while in several European countries, notably in France, external compression device, such as the Adjustable Continence Therapy (ACT®, Uromedia Inc., MN, USA) or the artificial urinary sphincter (AUS) AMS 800 (American Medical Systems, Minnetonka, MN, USA), are usually favoured. While several series have assessed the outcomes of various surgical treatment of intrinsic sphincter deficiency [START_REF] Cour | Intrinsic sphincter deficiency and female urinary incontinence][END_REF], studies comparing two treatment options are lacking. The aim of this study was to compare the outcomes of the ACT device to the one of the artificial urinary sphincter AMS 800 in the treatment of stress urinary incontinence due to intrinsic sphincter deficiency in women.

Methods

Study design

All the 61 women who underwent a surgical treatment for stress urinary incontinence due to intrinsic sphincter deficiency from 2007 to 2017 were included in a singlecenter retrospective study. Intrinsic sphincter deficiency was defined as the combination of a low urethral closure pressure (<40 cm H2O), loss of urethral mobility, and a negative Marshall/Bonney test (urine leakage on straining or coughing not corrected by urethral support). The artificial urinary sphincter AMS 800 was considered as the standard treatment in these patients during the study period. The ACT periurethral balloons became available in our center in 2011 and was used only in the following cases: moderate incontinence (subjectively defined as pad test < 200 g/24h), patients aged over 80 years and/or morbidly obese and/or lacking manual dexterity limiting the abilty to operate the sphincter pump,….) and/or with history of previous pelvic radiation therapy and/or patients who refused the implantation of an artificial urinary sphincter. From 2007 to 2011, all patients were offered AUS with no alternatives and from 2011 to 2017 patients with the aforementioned comorbidites and those with moderate incontinence were offered peri-urethral balloons and the other patients were offered an AUS (but some refused and preferred to receive peri-urethral balloons). In accordance with national guidelines [START_REF] Cour | Intrinsic sphincter deficiency and female urinary incontinence][END_REF], no other surgical treatment (e.g. fascial sling, bulking agents,…) was used to treat intrinsic sphincter deficiency during the study period. Hence, the inclusion criterion was: all female patients who underwent a surgical treatment for stress urinary incontinence due to intrinsic sphincter deficiency from 2007 to 2017.

The study was approved by the local ethics committee and was conducted following the principles of the Helsinki declaration. Consent from all study participants was obtained. The study was not supported by the industry. The primary endpoint was the functional outcome categorized as: cured (complete continence, i.e. no pads used), improved (decrease in number of pads per day or in urine leakage assessed through pad test) or failure (no decrease in number of pads per day or urine leakage assessed through pad test).

Adjustable Continence Therapy: device and surgical technique

All patients had a negative preoperative urine culture and received 2 g of Cephalosporin group 2 at the beginning of the procedure as antibiotic prophylaxis.

Patients with a positive preoperative urine culture (≥10 3 CFU/mL) received antibiotic treatment according to the sensitivity of the bacteria isolated from their urine culture for a minimum period of two days before the implantation.

The ACT® kit contains two silicone elastomer balloons connected to a titanium port, a seringe and a ponction needle used to inflate the device through the titanium port.

Balloons are available in 4 lengths from 6 to 9 cm, which will be determined using the trocar. This last tool is a part of dedicated tools with tipped stylet and a blunt-tipped stylet,.

The surgical procedure was performed as previously described by others [START_REF] Cour | Intrinsic sphincter deficiency and female urinary incontinence][END_REF][START_REF] Vayleux | Adjustable Continence Therapy in women, middle term follow-up and a new technique for balloon positioning[END_REF][START_REF] Phé | A Systematic Review of the Treatment for Female Stress Urinary Incontinence by ACT® Balloon Placement (Uromedica, Irvine, CA, USA)[END_REF][START_REF] Kocjancic | Adjustable Continence Therapy for Severe Intrinsic Sphincter Deficiency and Recurrent Female Stress Urinary Incontinence: Long-Term Experience[END_REF].

The balloons were placed at each side of the bladder neck using the trocar, which was inserted using an incision in each labia majora, and the devices were pushed laterally to urethra to their correct position on each side of the bladder neck, slightly posterior (at 5 o'clock and 7 o'clock) which was controlled by fluoroscopy and flexible cystoscopy. The balloons were filled with 0.6 ml of an aqueous radiopaque solution through the titanium port, which was placed subcutaneously in the labia majora. The trocar was removed after inflation of the device, in order to avoid moving the device during the removal.

A urethral catheter was introduced for up to 12 hours and removed before the patient was discharged. The procedure was performed as outpatient surgery when deemed possible.

ACT implantations were performed by two surgeons with no previous experience of this surgery before the study period. Inflations of 0.6 ml were performed once a month from 1 month post-operatively in outpatient clinics without any anesthesia by injecting into the titanium ports, until a satisfactory improvement was observed and up to a maximum of 7 ml per balloon.

Artificial Urinary Sphincter: device and surgical technique

The antibiotic policy used was similar to the one of ACT implantations (see above).

The device used was the AMS 800 in all cases. The surgical techniques used were those previously described and followed the same principles regardless of the approach [START_REF] Peyronnet | Artificial Urinary Sphincter Implantation in Women with Stress Urinary Incontinence: Preliminary Comparison of Robot-Assisted and Open Approaches[END_REF]. Briefly, the Retzius space was dissected until the bladder neck and the endopelvic fascia was opened on both sides of the urethra. The bladder neck was then dissected from the vagina below the periurethral fascia just below the level of the catheter balloon. The surgeon introduced two fingers of his left hand into the vagina to help the dissection. At the end of the dissection the bladder was filled with saline stained with methylene blue to verify the integrity of the bladder neck. The bladder neck circumference was measured using a measuring tape. The cuff was then positioned around the bladder neck. The pump was implanted in one of the labia majora and the balloon in the prevesical space. An open approach was used from 2007 to 2012 with a few laparoscopic cases over this period. From 2012 to 2017, all implantations were performed through a robot-assisted approach. A single surgeon (AM) highly experienced in functional urology performed all open and laparoscopic cases. He was then involved as the assistant surgeon on the surgical field for the robotic implantations while two consecutive surgeons were performing the dissection at the console: a first surgeon highly-experienced in robotic surgery (SV; > 600 robotassisted radical prostatectomy at the beginning of the present study) performed the first ten cases and a second surgeon, (BP, a young fellow who had performed only 20 robotic procedures before his first robotic AUS implantation) performed the subsequent cases.

The AUS were deactivated at the time of implantation and the urethral catheter was removed 2 days after surgery, bladder ultrasound was carried out to confirm adequate bladder voiding after catheter removal. Patients returned 6 weeks later for activating and learning to use the sphincter.

Pre and post-operative assessments

All patients underwent a complete work-up before surgery including: urodynamics, urethrocystoscopy, 3 days bladder diary, and pad test. The preoperative assessment also comprised a clinical interview, an urogynaecological examination and the Urinary Symptoms Profile (USP) [START_REF] Haab | Comprehensive Evaluation of Bladder and Urethral Dysfunction Symptoms: Development and Psychometric Validation of the Urinary Symptom Profile (USP) Questionnaire[END_REF] and the Internation Consultation on Incontinence Questionnaire Short Form (ICIQ-SF) questionnaires [START_REF] Avery | ICIQ: A Brief and Robust Measure for Evaluating the Symptoms and Impact of Urinary Incontinence[END_REF] (from 2011 to 2017). Neurogenic stress urinary incontinence was defined as stress urinary incontinence in a patients with spinal cord injury or spina bifida.

Follow-up involved an outpatient visit at 3 months, 6 months and 1 year postoperatively and then annually with a clinical examination, a 3 days bladder diary and an uroflowmetry with ultrasound measurement of post-void residual urine volume. An urodynamic testing was performed 3 months after AUS implantation to measure postoperative urethral closure pressure but was not performed routinely after ACT® implantation (only in case of persistent urinary incontinence after inflation of up to 5 ml per balloon).

Postoperative complications were graded using the Clavien-Dindo classification [START_REF] Dindo | Classification of Surgical Complications[END_REF] and were reported according to the EAU guidelines [START_REF] Mitropoulos | Reporting and Grading of Complications after Urologic Surgical Procedures: An Ad Hoc EAU Guidelines Panel Assessment and Recommendations[END_REF]. Failure was defined as explantation of the AUS device and divided into two categories: mechanical failure (perforation of any parts of the AUS or pump malfunction) and nonmechanical failure (cuff erosion, infection, pain, insufficient pressure). Hence, failure and continence status were analyzed separately and failure defined only the impossibility of maintaining the device in situ. Acute urinary retention was defined as a post-void residual volume > 150 ml postoperatively spontaneously resolving within the first 3 months after surgery. Chronic urinary retention was defined as the persistence of a post-void residual volume > 150 ml greater than three months after the implantation. per day).

Statistical analysis

Perioperative and functional parameters were compared between the two groups.

Means and standard deviations were reported for continuous variables, and proportions for nominal variables. Comparisons between groups were performed using the χ 2 test or Fisher's exact test for discrete variables, and Mann-Whitney test for continuous variables. Change of continuous variables over time was assessed using the McNemar test. Time to failure were estimated using the Kaplan-Meier method and compared between both groups using the log-rank test. Statistical analyses were performed using JMP v.12.0 software (SAS Institute Inc., Cary, NC, USA). All tests were two-sided with a level of p <0.05 considered statistically significant.

Results

Patients' characteristics

Over the study period, 61 patients were screened and all met the inclusion criterion: 25 underwent an ACT® implantation and 36 an AUS implantation. The study flowchart is shown in figure 1. The patients' characteristics are summarized in table 1.

Patients in the AUS group were younger (62.9 vs. 70.4 years; p=0.03) with less comorbidity (ASA Score=3 in 12.1% vs. 33.3%; p=0.005) and none had a history of previous pelvic radiation therapy conversely to those in the ACT® group (0% vs. 20%; p=0.009). More patients undergoing an AUS implantation had failed previous midurethral sling (66.7% vs. 40%; p=0.04) but the rate of neurogenic stress urinary incontinence was comparable between both groups (13.9% vs. 4%; p= 0.39) and the maximum urethral closure pressure did not differ significantly between the AUS and ACT® groups (27.3 vs. 28.8 cmH2O; p=0.61). The proportion of patients who had undergone a second midurethral sling was also similar in both groups (27.8% vs. 13.6%; p=0.21). The reasons for ACT® implantations were as follows: moderate incontinence in five patients (20%), comorbidites in 10 patients (40%) and 10 patients were offered an AUS but refused and then underwent implantation of ACT® (40%).

Eight and five patients in the ACT and AUS group respectively had not undergone any anti-incontinence surgical procedure (32% vs. 13.9%; p=0.12).

Perioperative outcomes

Operative time was shorter in the ACT® group (45.7 vs. 206.1 min; p<0.001) and so was the length of hospital stay (1.7 vs. 7 days; p<0.001). There was a higher rate of intraoperative complications in the AUS group (47% vs. 8%; p<0.001). The two intraoperative complications in the ACT® group were 1 bladder neck injury and 1 vaginal injury. The 17 intraoperative complications in the AUS group were 10 bladder neck injuries and 7 vaginal injuries. The rates of post-operative complications (40% vs. 47.2%; p=0.57) and of major post-operative complications (8% vs. 19.4%; p=0.28) did not differ significantly between both groups. There were two Clavien 3a complications in the ACT® group which were early vaginal erosions associated with a device infection which required explantation under local anesthesia in both cases.

In the AUS group, seven clavien 3b complications occurred; 5 device infections and two large erosions which required all an explantation of the AUS under general anesthesia. The last major complication in the AUS group was a device infection, which occurred after a change of a first sphincter that got infected and treated conservatively. It was almost always associated with a bladder neck injury during the procedure. No Clavien 4 or 5 complications occurred in both groups. After a mean follow-up of 44.3 months in the AUS group (vs 22.3 months in the ACT® group; p=0.02) the explantation rate were similar in both groups (19.4% vs. 20%; p=0.99).

All five explantations in the ACT® group were due to non-mechanical failure: It was due to device infection two cases, to symptoms worsening in two cases and in one case, ACT® were explanted before implantation of an AUS. Explantations in the AUS group were due to non-mechanical failure: Five were due to device infections; one to large vaginal erosion and one was explanted because of a bladder neck erosion.

When a mechanical failure occurred, we managed the situation with a surgical revision and it has always been done successfully. Time-to-failure is shown in figure 2 (12-months cumulative failure rate: 14% in the AUS group vs 22% in the ACT® group; p=0.42).

Functional outcomes

The mean number of inflations in the ACT® group was 2.9 per balloon and the mean final volume of each balloon was 3.4 ml. In the AUS group a 61-70 cm H2O pressure balloon was used in all except one case (71-80 cm H2O) and the median cuff size was 70 mm. The decrease in USP stress incontinence subscore was significantly greater in the AUS group (-7.6 vs. -3.2; p<0.001; supplementary figure 1) and so was the decrease in mean number of pads per 24h (-4.6 vs. -2.3; p=0.002; see table 3).

The Patient-Global Impression of Improvement (PGII) [START_REF] Yalcin | Validation of Two Global Impression Questionnaires for Incontinence[END_REF] was better in the AUS group (PGII=1: 61.1% vs. 12%; p<0.001) as was the rate of patients cured (71.4% vs. 21.7%; p<0.001). Five patients in the ACT® group required the use of cleanintermittent self-catheterization postoperatively, at least for some time, compared to only one in the AUS group (20% vs. 2.8%; p=0.04). Two of the five patients who experienced urinary retention in the ACT® group complained from this condition so their balloons were partly deflated and they recovered spontaneous voiding in both case.

Subgroup of persistent/recurrent stress urinary incontinence after midurethral slings

In this subgroup, no patients in the ACT® group had undergone previous pelvic radiation therapy. Mean age was similar in both groups (71.7 vs. 66.4; p=0.23; see table 4) and the maximum urethral closure pressure of patients who underwent an AUS or an ACT® implantations were comparable (24.9 vs. 26.4 cm H2O; p=0.64).

The proportion of patients who had undergone a second midurethral sling did not differ significantly between both groups (37.5% vs. 10%; p=0.21). The rate of intraoperative complications remained higher in the AUS group (54.2% vs. 10%; p=0.02).

The rate of post-operative complications tended to be higher in the AUS group (54.2% vs. 20%; p=0.13). The explantation rate did not differ significantly between the two groups (30% vs. 25%; p=0.99). AUS outperformed ACT® in terms of functional outcomes with a higher cure rate (66.7% vs. 30%; p=0.04) and a greater decrease in USP stress incontinence subscore (-8 vs. -5.3; p=0.003).

Discussion

According to the International Consultation on Urological Diseases (ICUD), stress urinary incontinence would affect from 5 to 15% and up to 30% in women over 70year old [15].. Two decades ago, the works of Ulmsten and DeLancey has changed the understanding of stress urinary incontinence by outlining the distinct role of urethral support and function of urethral muscles [16; 17]. This gave birth to the concept of intrinsic sphincter deficiency meaning an impaired sphincter functioning due to loss of elasticity and coaptation [START_REF] Mcguire | Diagnosis and Treatment of Intrinsic Sphincter Deficiency[END_REF]. While most of stress urinary incontinence in female patients is mainly due to urethral hypermobility, the exact proportion of these women who suffer from some degree of intrinsic sphincter deficiency remain unknown [START_REF] Cour | Intrinsic sphincter deficiency and female urinary incontinence][END_REF]. The optimal management of women with stress urinary incontinence due to intrinsic sphincter deficiency is still a matter of debate. While the American Urological Association (AUA) 2017 guidelines [19] do not mention the role of AUS or ACT® in their treatment algorithm; the European Association of Urology (EAU) 2017 guidelines consider that they might have a role but that secondary synthetic sling, colposuspension or autologous sling are first options for women with complicated stress urinary incontinence [20]. The French Association of Urology (AFU) recommends AUS as the gold-standard treatment for severe SUI due to intrinsic sphincter deficiency and ACT® as a possible alternative in these patients [21]. These heterogeneous recommendations may be explained by the paucity of data in the literature. To date, no study has compared fascial slings to AUS or ACT®. To our knowledge, the present series is one of the first to compare two different techniques of intrinsic sphincter deficiency management in female patients and the first to compare these two specific devices. In the present study, AUS implantation was associated with better functional outcomes than ACT® implantation in female patients with stress urinary incontinence due to intrinsic sphincter deficiency but with higher intraoperative complications rate, longer operative time and prolonged length of stay.

The morbidity of AUS implantation was higher than the one of ACT®, despite comparable post-operative complications rate. The high morbidity of the AUS in female patients has often been assumed to be the key factor that has limited its widespread [START_REF] Chartier-Kastler | Artificial Urinary Sphincter (AMS 800) Implantation for Women with Intrinsic Sphincter Deficiency: A Technique for Insiders?[END_REF]. This high complication rate might be due to the technically challenging dissection of the bladder neck, located deep in the pelvis with an urethral-vaginal septum often difficult to open due to the amount of previous surgical procedures. In recent years, the use of a robotic approach has been proposed to facilitate AUS implantation in women [22]. In a preliminary report, robotic AUS implantation appeared to decrease post-operative complications rate, blood loss and length of stay with a trend towards lower intraoperative complications compared to the open approach. Hence, one may assume that the difference we observed in terms of morbidity between AUS and ACT® may be tempered with a purely robotic AUS cohort (our cohort included a mix of open, laparoscopic and robotic AUS implantation).

It is now widely accepted through the urogynecology community that rather than looking for an objective cure in every case, physicians should adapt their treatments to patient's expectation and profile [23]. Our results are of interest in that regard as AUS, by outperforming ACT® in terms of functional outcomes, might be an appropriate option for patients with intrinsic sphincter deficiency seeking for cure of their urinary incontinence. Conversely, with its fair safety profile despite older patients with more comorbidity and previous pelvic radiation therapy (20%), the ACT® could be a reliable option for patients looking for improvement of their urinary incontinence.

Another point of interest of this study is that the ACT® was associated with an increased risk of urinary retention postoperatively. This finding emphasizes an important point of strength of the AUS, as it is the only therapy of stress urinary incontinence due to intrinsic sphincter deficiency increasing urethral pressure during storage while maintaining a low urethral resistance during voiding by opening the device cuff. Indeed, the mechanism of action of ACT® is similar to the one of other treatment options such as fascial slings or bulking agents, by creating a permanent (ie that cannot be relieved) external compression over the urethra to preserve continence [START_REF] Nadeau | Management of Recurrent Stress Incontinence Following a Sling[END_REF]. Long-term data regarding the impact of this increase bladder outlet resistance on detrusor contractility are lacking [24] but by analogy to what is seen in men with long-lasting benign prostate obstruction, one could assume that this external compression treatment options (i.e. ACT®, bulking agent or fascial sling) may lead to detrusor underactivity in the long-term. The benefits of ACT over bulking agents or fascial slings in that regard is that the obstruction can be fully relieved, as outlined in our series, by deflating the balloons.

Our study had several limitations that should be emphasized. Firstly, its retrospective and nonrandomized design could have partly flawed our results, notably because of an obvious selection bias with patients' characteristics differing in both groups, which we aimed to balance by performing a subgroup analysis. Another limitation is the relatively small sample size of our series, which may lead to a lack of statistical power and which prevented to perform multivariate analyses. We reported the early experience of a medium volume center for the two techniques and our findings may have differed if coming from a tertiary volume center with a larger experience in AUS and ACT® implantations. There is still no consensus regarding the definition of intrinsic sphincter deficiency and the one we used in this study could therefore be a matter of debate. The various approaches used in the AUS group (i.e. open, laparoscopic, robot-assisted) might have been a confounder when analysing perioperative outcomes. Despite these drawbacks, we believe that the comparative data we provide are of value while the optimal management of SUI due to intrinsic sphincter deficiency remains to be determined.

Conclusion

In the present series, the patients in the two groups differed significantly in age, ASA score, history of pelvic radiation therapy and history of previous midurethral sling, which might have biased our findings. AUS implantation was associated with better functional outcomes than the ACT® in female patients with stress urinary incontinence due to intrinsic sphincter deficiency but with higher intraoperative complications rate, longer operative time and length of stay. Post-operative complications and explantation rates were similar between both groups. Future prospective randomized trials are needed to better define treatment algorithms of female patients with stress urinary incontinence due to intrinsic sphincter deficiency.

Initial

Table 1 : Patients' characteristics

 1 Paul, and Julia Kargl. "Quality of Life and Urinary Incontinence in Women."

	Results."	Urology	84,	no.	5	(November	2014):	1094-98.
	doi:10.1016/j.urology.2014.07.013.
	23. Riss, Maturitas 68, no. 2 (February 2011): 137-42. doi:10.1016/j.maturitas.2010.11.006.
	24. Siddiqui, Zain A., Hamid Abboudi, Ruairidh Crawford, and Shahzad Shah.
	"Intraurethral Bulking Agents for the Management of Female Stress Urinary
	Incontinence: A Systematic Review." International Urogynecology Journal, February
	21, 2017, 1-10. doi:10.1007/s00192-017-3278-7.

* :statistically significant

Table 2 :

 2 Perioperative outcomes

		ACT® N=25	Artificial urinary N=36 sphincter	p-value
	Operative time (min)	45.7 (± 7.7)	206.1 (± 7.7)	<0.001*
	Length of hospital stay (days)	1.7 (± 1)	7 (± 0.9)	<0.001*
	Intra-operative complications	2 (8%)	17 (47%)	<0.001*
	Post-operative complications	10 (40%)	17 (47.2%)	0.57
	Major post-
	operative complications	2 (8%)	7 (19.4%)	0.28
	(Clavien ≥ 3)
	Explantation	5 (20%)	7 (19.4%)	0.99
	* : statistically significant

Table 3 :

 3 Functional outcomes

	ACT® N=25	Artificial urinary N=36 sphincter	p-value

* :

statistically significant 1 : statistically significant change from baseline (p<0.05)Table 4 : Subgroup of recurrent/persistent incontinence after midurethral slings

 4

		ACT® N=10	Artificial urinary N=24 sphincter	p-value
	Mean age (years)	71.7 (± 3.3)	66.4 (± 2.1)	0.23
	Maximum urethral closure pressure (cmH2O)	24.9 (± 3.5)	26.4 (± 2.5)	0.64
	Intra-operative complications	1 (10%)	13 (54.2%)	0.02*
	PGII (6 months)
	1 : Very improved	1 (10%)	15 (62.5%)
	2 : Improved 3 : Slightly improved	3 (30%) 4 (40%)	5 (20.8%) 2 (8.3%)	0.02*
	4 : Unchanged	1 (10%)	4 (16.7%)
	5-7 : Woresened	1 (10%)	1 (4.2%)
	Complete continence at 6 months	3 (33.3%)	16 (66.7%)	0.04*
	USP stress incontinence
	sub-score (/9)
	Preoperatively	7.8 (± 0.5)	8.4 (± 0.5)	0.22
	At 6 months	3.5 (± 0.6) 1	0.4 (± 0.5) 1	0.003*
	Explantation	3 (30%)	6 (25%)	0.99

* :statistically significant 1 : statistically significant change from baseline (p<0.05)

Abbreviations