Le Roux Enora

Menesguen Florence

Popelier Marc

Halbron Marine

Pauline Faucher

Pinto Graziella

Hatem Stephane

Polak Michel

Poitou Christine

Touraine Philippe
email: philippe.touraine@aphp.fr

Philippe Pr

Touraine

Transition of young adults with endocrine and metabolic diseases: The "TRANSEND" cohort All authors names and full addresses

Keywords: Transition to adult care, Endocrinology, Case Management, Cohort, Care pathway

Objective. The transition from paediatric to adult medicine involves risks of poor patient outcomes and of significant losses of patients to follow up. The research aimed to analyse the implementation in an initial cohort of patients of a new program of transition to adult care based on a case management approach.

Design. A longitudinal study of the case management approach to transition, initiated in a university hospital in France in September 2016.

Methods. Patients with endocrine or metabolic disease diagnosed during childhood and transferred to adult care were included. The transition program includes 3 steps based on case management: liaising with paediatric services, personalising care pathways, and liaising with structures outside the hospital (general practitioners, agencies in the educational and social sector).

Results. The cohort included 500 patients, with malignant brain tumour (n=56 (11%)), obesity (n=55 (11%)), type 1 diabetes (n=54 (11%)), or other disease (n=335 (67%)). Their median age at transfer was 19, and the sex ratio was 0.5. At median 21 months of follow-up, 439 (88%) had regular followup in or outside the hospital, 47 (9%) had irregular follow-up (absence at the last appointment or no appointment scheduled within the time recommended), 4 had stopped care on doctor's advice, 4 had died, 3 had moved, and 3 had refused care. The program involved 9,615 case management actions; 7% of patients required more than 50 actions. Patients requiring most support were usually those affected by a rare genetic form of obesity.

Conclusions. Case managers successfully addressed the complex needs of patients. Over time, the cohort will provide unprecedented long-term outcome results for patients with various conditions who experienced this form of transition.

INTRODUCTION

Metabolic and endocrine diseases in children and adolescents include more than 500 different diseases with an overall incidence of between 1: 2000 and 1: 4000 [START_REF] Saudubray | Les maladies héréditaires du métabolisme à l'âge adulte[END_REF]. The most common condition is type 1 diabetes, which has an incidence of about 15 cases per 100,000 children under the age of 15 [START_REF] Patterson | Incidence trends for childhood type 1 diabetes in Europe during 1989-2003 and predicted new cases 2005-20: a multicentre prospective registration study[END_REF], while the rarest have reporting incidences of less than one in every 1,000,000 children. These diseases differ according to the type of involvement (isolated or multisystemic), the organs affected, the age of disclosure and the need for paramedical or social care and support.

In recent decades, the survival rate of these paediatric patients has improved, and their care pathway now involves a transition to adult care around their age of majority. In the literature, this period is associated with poor outcomes that have various consequences for the health of young people: poor clinical results, disruptions of care, visits to emergency departments, hospitalisations and intensive care admissions, especially in endocrine diseases [START_REF] Lotstein | Transition From Pediatric to Adult Care for Youth Diagnosed With Type 1 Diabetes in Adolescence[END_REF][START_REF] Cadario | Transition process of patients with type 1 diabetes (T1DM) from paediatric to the adult health care service: a hospital-based approach[END_REF]. In addition, patients and families report low satisfaction with care and increased psychological distress during the transition [START_REF] Hepburn | Health system strategies supporting transition to adult care[END_REF].

For patients, in particular young people with various endocrine and metabolic diseases [START_REF] Polak | Transition of Care: From Childhood to Adulthood in Endocrinology, Gynecology, and Diabetes[END_REF], the transfer to adult care represents a major challenge. In paediatric care, young people generally have a longstanding relationship and are comfortable with a team familiar with their illness and with their personal and social history; however, consultations do not always adapt to meet the needs of adolescents and to encourage their empowerment [START_REF] Van Staa | Crossing the transition chasm: experiences and recommendations for improving transitional care of young adults, parents and providers: Crossing the transition chasm[END_REF]. Patients in adult care, who are considered autonomous, may consult a different caregiver at each visit, while consultations focus mainly on clinical outcomes and do not always address the psychosocial or developmental concerns of young people. Poorly prepared for the management of these paediatric patients, adult specialists may neglect the pathological past of the child and its consequences, both physical and psycho-social [START_REF] Monaghan | Transition Readiness in Adolescents and Emerging Adults with Diabetes: The Role of Patient-Provider Communication[END_REF].

To deal with this situation, recommendations have been developed internationally to support successful transition from paediatric to adult care [START_REF]A consensus statement on health care transitions for young adults with special health care needs[END_REF][START_REF]Transition to adult care for youth with special health care needs[END_REF][START_REF] Singh | Supporting young people in their transition to adults' services: summary of NICE guidance[END_REF]. However, most of the content of these recommendations focuses on paediatric preparation. They advocate ongoing information about transition throughout the care pathway, inclusion of the family, consideration of developmental aspects, patient education and specific resources, coordination with primary care, and flexible adaptation of the moment of transfer to the individual case. Several programs have been developed and published, showing that a prepared and coordinated transition can have a positive impact on patients' health, their experiences of care and the use of care. In a systematic review published in 2017, only 6 of the 39 [START_REF] Gabriel | Outcome Evidence for Structured Pediatric to Adult Health Care Transition Interventions: A Systematic Review[END_REF] identified transition programs were delivered in adult services [START_REF] Roux | Methodology used in comparative studies assessing programmes of transition from paediatrics to adult care programmes: a systematic review[END_REF], and 5 were dedicated exclusively to young people with type 1 diabetes. The same review showed that programs developed for a specific pathology may be appropriate for young people with various diseases. The published programs are generally accessible only to some individuals on the active patient list: 20% of programs exclude young people with an intellectual disability [START_REF] Roux | Methodology used in comparative studies assessing programmes of transition from paediatrics to adult care programmes: a systematic review[END_REF]. Finally, the timing of data collection after patient transfer enables assessment of the short-and medium-term outcomes of the interventions, but rarely of longer-term ones [START_REF] Roux | Methodology used in comparative studies assessing programmes of transition from paediatrics to adult care programmes: a systematic review[END_REF].

It is in this context that a new program of transition based on case management has been developed in a French adult hospital for young people with various endocrine and metabolic diseases. The development project was based on a survey, conducted by the team involved, of the difficulties faced during transition by young adults with congenital adrenal hyperplasia, hypogonadotropic hypogonadism and growth hormone deficiency [START_REF] Godbout | Transition from Pediatric to Adult Healthcare: Assessment of Specific Needs of Patients with Chronic Endocrine Conditions[END_REF]. The need for development of such a program was reinforced by a second survey showing an association between successful transition to specialist adult care and better health-related quality of life and regular medical follow-up in adulthood [START_REF] Bachelot | Impact of transition on quality of life in patients with congenital adrenal hyperplasia diagnosed during childhood[END_REF]. The very large number of patients shown to be lost to follow up in this study motivated the development of the TRANSEND project to reconsider the organisation of transition to adult care. Although these surveys focused on specific pathologies, the conclusions and implications that could be drawn concerned a larger group of patients; the TRANSEND project was therefore developed to meet the needs of all chronically ill patients during the transition rather than the specific requirements of a particular disease.

In the light of these observations, the objective was twofold: firstly to implement a transition program in an adult care department that meets the needs of patients and fulfils the recommendations, and secondly to collect data on a large number of patients in transition to study their long-term outcomes.

The TRANSEND program takes place in an adult hospital (hospital de la Pitié-Salpêtrière, Paris, France) in the endocrinology, nutrition and diabetology departments. The steering committee (made up of doctors from the three departments involved) defined the TRANSEND program as a dedicated care pathway for patients in transition, where a case manager has a central role in adapting and coordinating for each patient, from their discharge from paediatric services to their strong attachment in adult services.

The specific objective of the present study was to describe the initial cohort of patients and analyse their experience of a transition managed under the new program based on a case management approach.

MATERIALS AND METHODS

Patients

All the patients cared for by hospital-based paediatricians in transition to adult care, aged less than 25 at transfer and referred to services of nutrition, diabetology or endocrinology (metabolism, reproduction, thyroid and endocrine tumours) were included in the transition program and constitute the study cohort. The study is reported according to the STROBE Statement (16) (Supplementary material 1).

Description of the transition program

A medical steering committee for the TRANSEND program development was created comprising the doctors from the nutrition, diabetology, and endocrinology services t. Meetings and informal interviews were carried out with all the professionals of these services involved in the transition (nurses, social workers, psychologists, dieticians, medical secretaries). The information and opinions collected have been combined with the findings of surveys carried out in the department, to define a care pathway for patients in transition. This development phase was done in parallel with the recruitment of the case manager. The developed program involved three steps based on case management (Figure 1).

Step 1 is dedicated to liaising with paediatric services and patients to facilitate the patient's first visit to adult care (transfer of the file, call-up of the patient, file presentation by transition staff).

Step 2 defines the care pathway in adult service. Upon arrival in the adult service, patients coming from paediatrics systematically meet the case manager and their new doctors. The meeting takes place in a dedicated TRANSEND room, youth-friendly and adapted to all types of mobility and bodily need.

The case manager assesses the needs of each patient using interview and questionnaires (on social needs, patients' expectations and patients' autonomy) to offer them a personalised pathway in the hospital involving the different available resources and professionals (medical, paramedical, social).

Throughout the follow-up, care pathways are supervised by the case manager, who is identified as the key contact by the patients, and who is reachable by text, phone or mail.

Step 3 focuses on liaising with structures outside the hospital (general practitioner, agencies in the educational and social sectors), to improve the long-term follow-up of patients, and to enhance widescale coordination of the life project (ensuring that the patient has appropriate training and employment, a suitable place to live, social activities). (See all the details of the care approach in TidiER checklist [START_REF] Hoffmann | Better reporting of interventions: template for intervention description and replication (TIDieR) checklist and guide[END_REF] -Supplementary material 2)

The program was launched in September 2016, with a full time case manager and a dedicated place in the adult hospital concerned. The program is dynamic and has evolved each year since its launch, the evolutions are discussed and decided with the steering committee. Additional elements based on the observation of patients' needs have been added over time: additional time dedicated to coordination, creation of explanatory leaflets about patients' diseases intended for professionals outside the hospital, dedicated therapeutic education sessions, questionnaires that allow to complete the tools available for the patients' needs' assessment (questionnaire to define patient expectations developed specifically for the program, questionnaire to assess patients' autonomy using the Good2Go ( 18)).

Data collection and statistical analysis

The data used were collected as part of the case manager's routine activity of monitoring and filing activity reports. The sources of data are the patient's medical file and the case report form used by the case manager in routine collection of all the individual data of the patients related to their arrival and follow-up in the TRANSEND program prospectively. These data are summarised and not identifiable, and their collation does not require Institutional Review Board approval according to European or A descriptive analysis was conducted on the data collected between the launch of the program in September 2016 and the first interim analysis realised in March 2020. Results were reported as median (Q1, Q3) for continuous variables and as frequency counts and percentages (%) for categorical variables.

RESULTS

Since its launch, 500 patients have experienced the TRANSEND program (patients with at least one visit). The distribution of the first visits in the program per year has been consistent in time: 144 took place in the first year of the launch, 134 in the second year, 140 in third year, and 82 during the first half of the fourth year. The mean follow up time in the program is 21 months (min : 0 ; max : 42). The majority of patients make their transition from a hospital at a regional level (471/500, 94%), 14 from a hospital outside the regional level, 11 from a private practitioner, and 4 from the social or voluntary sector. Patients included in the program had more than 15 different medical conditions; the main diagnoses and patients' health characteristics are presented in Table 1. Patients had diverse sociodemographic profiles (Table 2) resulting in complex and diverse needs for support.Over the period, the case manager performed 9615 coordination actions, from 1 to 461 per patient. These involved meetings, telephone conversations and emails, with the patient, the family, and intra-and extrahospital partners. Actions relating to the TRANSEND program (call before first visit, plan and deliver the first meeting between patient and case manager) and to the link with paediatrics (request for medical records), represent 2734 (28%) of coordination actions. Management of hospital appointments (consultations with a doctor or other professional, hospitalisations, delay or postponement of appointments, reminders in case of appointments not scheduled or not attended, requests for transportation vouchers, admission procedures, information on hospital and services, etc.) represent 3389 (35%) of coordination actions. Follow-up of patients (medical issues, social issues, links with community / private practice, other hospitals, medical-social establishments, paramedical, organisation of neuropsychological assessments) represent 3492 (36%) of coordination actions.

For the 33 (7%) patients whose transition required more than 50 actions, a median of 82 actions were performed. Of these patients, 20 (61%) have obesity (the majority having a rare genetic form of obesity).

The case manager planned care with a dietician for 148 (30%) patients, with a psychologist for 95 (20%) patients, and with a social worker for 44 (9%) patients. Patient education, in groups, was delivered to 34 (8%) patients. A third of patients (n=156) had a second individual facilitation meeting with the case manager, at the request of the doctor, especially during hospitalisation. Of the 500 patients in the cohort, 416 (83%) have regular follow-up in the hospital (next consultation already scheduled and / or within the recommended time limit for the next consultation), 23 (5%) are being followed in another hospital or in a private practice, 47 (9%) have irregular follow-up (absence at the last appointment or no appointment scheduled within the time recommended by the doctor), 4 have stopped care in a hospital setting on the doctor's advice, 4 have died (3 fatal outcomes of a brain tumour, 1 accident related to an epilepsy seizure), 3 have moved, and 3 have refused care. Among those with regular or irregular follow-up, 149 (30%) were called once or several times to unattended and / or unplanned appointments. Among these patients, 86 (58%) scheduled a new appointment. The reasons given for the irregularity of the follow-up were resistance to medical follow-up (asymptomatic or sceptical patients), concerns linked to life projects (studies, work, their sociology-medical support agency) or to other medical care (oncology, psychiatry, neurology, etc.) and social and family difficulties (no parental support, lack of autonomy). No diagnosis is clearly overrepresented in these patients.

DISCUSSION

In 3 years of activity, the TRANSEND program has demonstrated the possibility of sharing of resources between different services and the acceptance by all professionals in an adult care department of a new organisation and a new worker (the case manager) to improve transition care by providing coordination of care and adapting support to the needs of the patients. The program acceptance is supported by the fact that all patients arriving in this department have been referred to the case manager since the launch of the program, regardless of the doctor in charge. This acceptance is probably enhance by the fact that the TRANSEND program has developed in response to a locally identified need: that of young patients lost to follow-up during transition [START_REF] Godbout | Transition from Pediatric to Adult Healthcare: Assessment of Specific Needs of Patients with Chronic Endocrine Conditions[END_REF][START_REF] Bachelot | Impact of transition on quality of life in patients with congenital adrenal hyperplasia diagnosed during childhood[END_REF]. The acceptability has also been probably strengthened by the involvement of the professionals of the department since the beginning in the steering committee, which developed and made the TRANSEND program evolve.. The TRANSEND program was developed based on the needs of young patients identified in the international literature,which found a lack of awareness of psychosocial and developmental aspects and coordination in adult care [START_REF] Peters | Diabetes Care for Emerging Adults: Recommendations for Transition From Pediatric to Adult Diabetes Care Systems: A position statement of the American Diabetes Association, with representation by the American College of Osteopathic Family Physicians, the American Academy of Pediatrics, the American Association of Clinical Endocrinologists, the American Osteopathic Association, the Centers for Disease Control and Prevention, Children with Diabetes, The Endocrine Society, the International Society for Pediatric and Adolescent Diabetes, Juvenile Diabetes Research Foundation International, the National Diabetes Education Program, and the Pediatric Endocrine Society[END_REF] but also based on the local needs of young people, relying on local surveys. The program is based on a patient-centred care approach. The case manager and overall organisation enable provision of care that is respectful of, and responsive to, individual patient preferences, needs and values [START_REF]Crossing the Quality Chasm: A New Health System for the 21st Century[END_REF]. It follows international recommendations on transition by providing information about transition, including to patients' families, considering the developmental aspects, allowing access to patient education and specific resources, and coordinating with primary care; these are particularly valuable and rare in routine adult medical care.

To our knowledge, the TRANSEND cohort is the largest and the most diversified in terms of patient profile in the field of transition. This cohort, whose data are collected routinely, reflects the real life of the program outside any interventional framework. The cohort study will be enriched over the years with other data (care use, self-management, and satisfaction) and new patients. It will result in longerterm study of young people with multiple diseases in post-transition, and identification of factors linked to long term outcomes and unmet needs to inform the evolution of TRANSEND. This continuous improvement of the program is already in progress, based on questionnaire completion by patients who report their needs to the case manager. lastly it also enables the identification of the young patients' need for more exchange between them.

The TRANSEND program includes patients with various diseases, with or without intellectual disability or in socially complex situations, which will ensure a high external validity for its results.

The choice to build a cohort allows for equity in access to quality care. In clinical trials one of the constraints is to select a homogeneous population to gain in precision (often at the expense of patients with complex profiles); this cohort study makes it possible to systematically include the patients followed in the department and subsequently to study all patient profiles, their different needs in terms of accompaniment during transition, and their long term outcomes. Although the transition program offered to patients in this cohort is intended to be universal, a limit is observed. A subgroup of patients in the cohort requires a large number of time consuming actions from the case manager, which was not planned at the outset: a variation of the program to better adapt to the different patient profiles could be considered.

According to a systematic review published in 2016, there is a lack of data from prospective studies on adult care attendance by patients in transition, and few studies have reported attendance in adult care at more than one year after transfer [START_REF] Rachas | Evaluating Continuity During Transfer to Adult Care: A Systematic Review[END_REF]. In a retrospective study of congenital adrenal hyperplasia patients, 50% were lost to follow-up after transfer to adult care, with no difference between those who transitioned through a young person clinic and those who did not [START_REF] Gleeson | The challenge of delivering endocrine care and successful transition to adult services in adolescents with congenital adrenal hyperplasia: experience in a single centre over 18 years[END_REF]. The same rate was reported in our department before the implementation of the TRANSEND program in patients with this same disease [START_REF] Bachelot | Impact of transition on quality of life in patients with congenital adrenal hyperplasia diagnosed during childhood[END_REF]. In another study evaluating the effect of an endocrinology transition clinic for patients with diverse diseases, adherence to adult care was 83% [START_REF] Twito | The "combined team" transition clinic model in endocrinology results in high adherence rates and patient satisfaction[END_REF]. In diabetes care, a recent literature review reported that in the absence of a formal transition process for patients with type 1 diabetes, the proportion of patients lost to follow up is reported as between 11% and 62% [START_REF] White | Transition to adult endocrine services: What is achievable? The diabetes perspective[END_REF]. Although data collection methods, post-transfer evaluation times, and definitions of "patient lost to follow up" are heterogeneous and make comparison difficult, the continued attendance rate reported in the TRANSEND cohort is much higher than those reported in the literature on young adults with endocrine and metabolic diseases.

A key issue in transition programs is their financial sustainability [START_REF] Hobart | Pediatric-to-adult healthcare transitions: Current challenges and recommended practices[END_REF]. With 500 active patients the case manager works full-time. The timing of patient exit from the program, initially planned when the patient is 25 years old, seems to have to adapt to the patient's needs. Prioritisation of actions and tasks delivered by the case manager becomes needed with the growth in numbers of patients in the cohort.

For example, the necessary coordination with professionals outside TRANSEND remains a challenge: the involvement of private practice medicine, the handover in hospital services and links with paramedics remain fragile after several years of existence of the program. The upcoming evaluation of the costs associated with the program and also of savings (including savings of costs of avoidable care) will help to better inform the relevance and cost-benefit analysis of the program.

The principle of equivalence would not have been respected if the impact of TRANSEND was evaluated in a randomised trial against usual forms of care. Previous usual care practice did not adapt to the situation of transition or to young adults' specific needs. Given the reported data on morbidity and mortality associated with interruptions of care during transition [START_REF] Sheehan | The experiences and impact of transition from child to adult healthcare services for young people with Type 1 diabetes: a systematic review[END_REF], it did not seem ethical to expose the patients of a control group to additional risks of serious or irreversible damage from not receiving an intervention based on recommendations.

However, a comparative non-randomised evaluation of TRANSEND is currently underway. It compares the post-transition outcomes in patients who transferred to adult care before TRANSEND to those who transferred after its implementation and benefited from it. The evaluation is based on the set of successful transition consensual indicators [START_REF] Suris | Key Elements for, and Indicators of, a Successful Transition: An International Delphi Study[END_REF] as well as a medico-economic assessment.

To conclude, the TRANSEND cohort shows that case-management upon arrival in adult care enhances satisfactory results with regard to follow-up after transfer from paediatrics: 88 % have regular followup and only 4 patients in 500 are confirmed as lost to follow-up (0.6%). Achieving these results involved significant deployment of resources: nearly 10,000 actions of case-management have been performed for the entire cohort.

DECLARATION OF INTEREST

There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

FUNDING

The transition program (dedicated room and case-manager funding) was supported by the "Hôpitaux de Paris -Hôpitaux de France" Foundation ("Transition program" Grant, 2015). The realisation and analysis of the cohort did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.

Scholarship or professional status (MD=13)

Post graduate studies 199 (40)

High school or vocational school 117 [START_REF] Twito | The "combined team" transition clinic model in endocrinology results in high adherence rates and patient satisfaction[END_REF] Medico-pedagogic institute 91 [START_REF] Mellerio | Validation of the "Good2Go": the first French-language transition readiness questionnaire[END_REF] No activity 39 [START_REF] Monaghan | Transition Readiness in Adolescents and Emerging Adults with Diabetes: The Role of Patient-Provider Communication[END_REF] Ordinary work 33 [START_REF] Van Staa | Crossing the transition chasm: experiences and recommendations for improving transitional care of young adults, parents and providers: Crossing the transition chasm[END_REF] Adapted to disability work

  French regulations (Regulation (Eu) 2016/679 Of the European Parliament and of the Council of 27 April 2016 and repealing Directive 95/46 / EC (General Data Protection Regulation)).

Figure 1 :

 1 Figure 1 : Schematic representation of the TRANSEND care pathways

Figure 1 :

 1 Figure 1: Schematic representation of the TRANSEND pathway.

6 2 A 9 .

 629 criteria, and the sources and methods of selection of participants. Describe methods of follow-up 5 Participants Page 21 of 31 Accepted Manuscript published as EC-20-0520. Accepted for publication: 24-Nov-2020 Copyright © 2019 the authors Downloaded from Bioscientifica.com at 01/08/2021 02:19:23PM via Bib Interuniversitaire Scien Jussieu Biologie Rech and Bupmc -Bibliotheque Numerique of interest, give sources of data and details of methods of assessment (measurement). Describe comparability of assessment methods if there is more than one ) Report numbers of individuals at each stage 7 of study-eg numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed (b) Give reasons for non-participation at each stage N/A (c) Consider use of a flow diagram N/A (a) Give characteristics of study participants (eg demographic, clinical, social) and information on exposures and potential Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (eg, 95% confidence interval). Make clear which confounders were adjusted for and why they were included If relevant, consider translating estimates of N/A relative risk into absolute risk for a the study, taking into account sources of potential bias or imprecision. Discuss both direction and magnitude of any potential bias of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article for patients in transition to adult endocrinology services after discharge from the paediatric services. to facilitate the healthcare pathway of young adults in transition from paediatric to adult care in the objective to avoid rupture in care during this pivotal period. in a dedicated room designed for young adults, in which flyers and information brochures are arranged (social initiatives, associations, etc.). Specific materials were developed for the program and are used during patient interviews with the case manager: interview a list of actions to be carried out and free notes), social questionnaire (designed by social workers) and corresponding doctor's cards. "Rare diseases" practical sheets (produced by doctors) inform on the specific surveillance measures of these diseases. They are distributed to the patient and/or sent to their general practitioner. A numeric version of these files is available on the hospital's intranet. Transition patient education tools and projection equipment and tablets (intended for meetings between professionals and patient groups) are stored in the TRANSEND room and offices. The steering committee (made up of doctors from the three departments involved) defined a care pathway for patients in transition, divided into three steps. Step 1 is dedicated in liaising with paediatric services and patient to facilitate its first visit in adult care (transfer of the file, call of the patient, file presentation in transition staff). The inclusion of patients in transition in TRANSEND is systematic for adolescents and young adults having a chronic endocrine pathology, referred by paediatrics, and having a consultation in one of the adult departments of endocrinology-reproductive medicine, nutrition, diabetology, endocrinologymetabolic diseases. Step 2 defines the care pathway in adult service. Upon arrival in adult service, the patients coming from paediatrics systematically meet the coordinator and their new doctors. The coordinator assesses the needs of each patient to offer them a personalised pathway in the hospital involving the different available resources and professionals (medical, paramedical, social). Thorough the follow-up, care pathways are supervised by the coordinator, who is identified as the key contact by the patients, who is reachable by text, phone or mail. Step 3 focuses in liaising with structures outside hospital (GP, educational and social sector), to improve the long-term follow-up of patients, and to enhance large scale coordination of the project of life. , a medical steering committee was built with the doctors from the services of Nutrition, Diabetology, and Endocrinology for the TRANSEND program development. For the regular monitoring of the program since its launch, a TRANSEND project committee was created and is composed of the medical project manager (head of the endocrinology department), the psychologist coordinating the transition patient education program, the responsible of the transition database and the case manager. The case manager is full-time on the TRANSEND program. She holds a state diploma in psychomotricity and a master's degree in rehabilitation and medical engineering, and a specialty in neurological disability in adults. This position requires clinical and professional network knowledge. telephone interview with the patient takes place before his first meeting with the coordinator in the TRANSEND dedicated room. A second meeting with case manager may be organised during an hospitalisation. These are individual interviews, but the patient may be accompanied by his parents. Patient education sessions are provided to few patients, in individual meeting or in little groups. individually or in a group. The patient care pathway and hospital appointments are monitored by the case manager thanks to the hospital intranet and result (if necessary) in calls of patients (consultation reminder or reschedule) takes place in an adult hospital (hospital de la Pitié-Salpêtrière, Paris, France) in the endocrinology, nutrition and diabetology departments. The TRANSEND room is equipped for individual interviews and for groups. It is accessible to people with reduced mobility. The furniture is youth-friendly and suitable for all body types. Patient monitoring takes place in the case manager office with computer and phone. started in September 2016. Two and a half years later, the cohort of patients in transition is 500. Details are in the results part of the article. TAILORING If the intervention was planned to be personalised, titrated P8 The first meetings with the case manager are carried out systematically at the start of care in the adult department. or adapted, then describe what, why, when, and how. On the other hand, consultations with the doctors of the service, planning of social worker appointment or proposition of patient education are determined individually according to the needs of the patient, by the case manager in consultation with the healthcare team. the subject of activity reports every six months since September 2016, written by the case manager.The project committee meets every month to review program data and discuss optimisation and / or evaluation.

Table 1 :

 1 Cohort medical characteristics

	Diseases

Table 2 :

 2 Cohort socio-demographic characteristics

	Med (Q1-Q3)

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ACKNOWLEDGEMENTS

We would like to thank all the nurses, social workers, dieticians, psychologists, and medical secretaries from the departments involved in the TransEND cohort for participating in the elaboration of the program. We would also like to thank Mrs E Benmansour, Mr S Morel, previous directors of Pitié Salpêtrière Hospital for their support for our proposal to set up such a program. Finally, we would like to thank Pr A Basdevant, Mr F Le Magny and Referis consultants for their advice in building up this program.

The Transend group includes all those doctors who refer their patients to the program and/or follow them in adult care: Prs and Drs. Afenjar, Aigrain, Amoura, Amouyal, Amsellem Jager, An, Andreelli, Azar, Bachelot, Belien Pallet, Beltrand, Bibal, Bidet, Bismuth, Blanc, Bodemer, Bougneres, Bourron, Bouvattier, Brauner, Brioude, Bruckert, Brugieres, Brune, Brunel, Burggraeve, Cabrol, Cacoub, Carel, Carlier, Carreau, Cassuto, Cessans, Chakhtoura, Cheikhelard, Chevignard, Ciangura, Consoli, Couderc, Coupaye, Courtillot, Da Costa, Dabbas, Dalla Vale, Dassa, De Beaufort, De Kerdanet, Delanoe, Delcroix, Diene, Dierick-Gallet, Donadieu, Dormoy, Doummar, Doz, Dubern, Dufour, Duranteau, Esteva, Fayech, Fiot, Flandrin, Flechtner, Fresneau, Gajdos, Gallo, Gaspar, Gelwane, Ghander, Giabicani, Gonzalez, Grill, Guilmin-Crepon, Grouthier, Hartemann , Haye, Heide, Houang, Ibrahim, Idbaih, Istanbullu, Jacqueminet, Jacquin, Jeandidier, Jeannin, Karsenty, Kenigsberg, Kipnis, Le Bastard, Le Poullenec, Leenhardt, Lefevre, Loison, Lorenzini, Lucidarme, Ly, Manh, Martinerie, Masson, Meneret, Mignot, Milcent, Mircher, Mochel, Moretti, Mosbah, Mourre, Moutafoff-Borie, Muller, Nasser, Navarro, Pasqualini, Paulsen, Pauwels, Personnier, Phan, Piquard Mercier, Porquet-Bordes, Puget, Ribeiro Parenti, Ricour, Rigaux, Robert, Robin, Rougeoreille Cretier, Samara Boustani, Sarnacki, Sauvion, Semeraro, Simon, Storey, Thalassinos, Tounian, Trang, Tubiana-Rufi, Villanueva, Whalen, Zaarour, Zenaty.


Kunche Aravindu

Eric Cloutet

Cyril Brochon

Georges Hadziioannou

Joan Vignolle

Frédéric Robert

Daniel Taton
email: taton@enscbp.fr

Yannick Landais
email: yannick.landais@u-bordeaux.fr

Poly(arylene vinylene) Synthesis via a Precursor Step-Growth Polymerization Route Involving the Ramberg-Bäcklund Reaction as a Key Post-Chemical Modification Step

Keywords: Ramberg-Bäcklund reaction, Poly(fluorene vinylene), Poly(fluorene vinylene-co-carbazole vinylene), Step-growth polymerization, π-Conjugated polymers

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INTRODUCTION

In recent years, thin-film device technologies employing π-conjugated polymers have attracted a great deal of attention owing to their properties suitable for electronic and optoelectronic applications, including organic transistors, [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF][START_REF] Swager | 50th Anniversary Perspective: Conducting/Semiconducting Conjugated Polymers. A Personal Perspective on the Past and the Future[END_REF] bulk heterojunction solar cells for organic photovoltaics (OPV) [START_REF] Granstrom | Laminated Fabrication of Polymeric Photovoltaic Diodes[END_REF][START_REF] Gunes | Conjugated Polymer-Based Organic Solar Cells[END_REF] or organic light emitting diodes (OLED). [START_REF] Grimsdale | Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices[END_REF] The solution-processability of π-conjugated polymers, combined with their optoelectronic properties, such as light absorption, carrier mobility and exciton dynamics, can be fine-tuned through subtle changes in their structure. Molecular parameters include molecular weight, bond length alternation, substituent effects, aromaticity, planarity, regioregularity, intermolecular interactions, etc. Hence, simple synthetic modifications can dramatically impact optoelectronic and thin film self-assembled properties. Most π-conjugated polymers consist of sp [START_REF] Swager | 50th Anniversary Perspective: Conducting/Semiconducting Conjugated Polymers. A Personal Perspective on the Past and the Future[END_REF] -hybridized carbon atoms and are based on aryl-aryl or aryl-vinyl repeating units, mostly through alternation between C-C and C=C bonds. [START_REF]Handbook of Conducting Polymers[END_REF] Heteroatoms can be introduced in the π-conjugation system: for instance, the -C=Ndouble bond is somehow electrically equivalent to the -C=C-one.

In this context, poly(p-phenylene vinylene)-(PPV)-type π-conjugated polymers represent a special class of highly fluorescent, highly stable polymeric semiconductors. [START_REF] Burroughes | Light-emitting Diodes Based on Conjugated Polymers[END_REF][START_REF] Morin | Syntheses and Characterization of Electroactive and Photoactive 2,7-Carbazolenevinylene-Based Conjugated Oligomers and Polymers[END_REF] PPV-like materials can be synthesized by a wide variety of synthetic routes, either following a step-growth or a chain-growth polymerization pathway. Step-growth polymerization methods directly leads to PPV oligomers and rely on well-established elementary reactions of molecular chemistry, such as the Knoevenagel condensation, [START_REF] Morin | Syntheses and Characterization of Electroactive and Photoactive 2,7-Carbazolenevinylene-Based Conjugated Oligomers and Polymers[END_REF] the Wittig or Horner-Wadsworth-Emmons olefination, [START_REF] Davey | Synthesis and Optical Properties of Phenylene-vinylene Copolymers[END_REF][START_REF] Anuragudom | Facile Horner-Emmons Synthesis of Defect-Free Poly(9,9-dialkylfluorenyl-2,7-vinylene)[END_REF][START_REF] Liu | Synthesis and Chain-Length Dependent Properties of Monodisperse Oligo(9,9-di-n-octylfluorene-2,7-vinylene)s[END_REF] the palladium-catalyzed Stille, Suzuki or Heck coupling [START_REF] Scherf | Design and Synthesis of Extended π-Systems: Monomers, Oligomers, Polymers[END_REF] and the Siegrist reaction. [START_REF] Meier | The Photochemistry of Stilbenoid Compounds and Their Role in Materials Technology Angew[END_REF] Alternatively, chain-growth polymerization methods allow achieving higher molecular weights. However, the final PPV material is often obtained by post-chemical modification of a polymer precursor as for instance in Gilch, [START_REF] Neef | MEH-PPV: Improved Synthetic Procedure and Molecular Weight Control[END_REF] Wessling sulfonium, 15- 16 dithiocarbamate (or xanthate), and sulfinyl routes. [START_REF] Dilien | A Deeper Insight into the Dithiocarbamate Precursor Route: Synthesis of Soluble Poly(thienylene vinylene) Derivatives for Photovoltaic Applications[END_REF][START_REF] Henckens | Synthesis of 3,4-Diphenyl-Substituted Poly(Thienylene Vinylene), Low-Band-Gap Polymers via the Dithiocarbamate Route[END_REF] In order to alleviate solubility issues and facilitate their processability, specific groups can be introduced in 2-and 5-positions of the aromatic ring of PPV-type materials. Controlled living polymerization has also been considered for PPV synthesis. [START_REF] Zaquen | Controlled/Living Polymerization Towards Functional Poly(p-phenylene vinylene) Materials[END_REF] With the exception of PPV's grown both by the latter method under specific conditions and by ringopening metathesis polymerization (ROMP), relatively poor control over molecular weights and dispersities generally characterize these polymerization routes. More generally, these synthetic methods to PPV's, although straightforward, still show some limitations, including: (a) structural defects due to incomplete post-chemical modification by thermal conversion or oxidation (b) modest molecular weights (c) generation of toxic side products during the elimination process (d) gelation or precipitation of the polymeric products, which may occur during polymerization (e) limited control over the E/Z content of the vinyl bridge (f) use of costly and non-renewable metal catalysts and, last but not least, (g) the presence of residual metallic traces, which require lengthy and tedious purification steps. [START_REF] Junkers | Synthesis of Poly(pphenylene vinylene) Materials via the Precursor Routes[END_REF] On this basis, we envisioned developing novel PPV-like materials following a previously unexplored precursor step-growth polymerization route/post-chemical functionalization sequence, involving a threestep sequence of reactions (Figure 1). The first step (i) is achieved by step-growth polymerization in solution of dibromides and dithiols as monomers, forming polysulfides. The second step (ii) consists in oxidizing these polymer precursors into polysulfones, which is followed by an ultimate step (iii) of elimination, via the so-called Ramberg-Bäcklund reaction. [START_REF] Taylor | The Ramberg-Bäcklund Reaction[END_REF] The Ramberg-Bäcklund reaction is very versatile for the construction of carbon-carbon double bonds, and has been largely applied in the context of total synthesis of complex natural products. Only recent reports have described its application in dendrimer synthesis. [START_REF] Chow | Dendrimer Interior Functional Group Conversion and Dendrimer Metamorphosis-New Approaches to the Synthesis of Oligo(dibenzyl sulfone) and Oligo(phenylenevinylene) Dendrimers[END_REF] This reaction involves a suitably designed sulfone precursor, which upon αhalogenation under basic conditions, provides the corresponding olefin generally in high yields. It is thus a simple way to create C=C double bonds under mild conditions, starting from readily available substrates. Another advantage of this process is that it allows the coupling around the sulfonyl group of identical or differentiated substituents, on purpose, in a limited number of steps. Starting materials are easily available and provide olefins without alkene rearrangements under mild alkaline conditions. E/Zstereocontrol mainly relies on the nature of the base, with mild bases favoring the Z-isomer, while E-is generally formed in the presence of stronger bases. Many examples have demonstrated that the Ramberg-Bäcklund process can be applied to the preparation of polysubstituted alkenes, including tetrasubstituted ones as well as polyenes. [START_REF] Taylor | The Ramberg-Bäcklund Reaction[END_REF] Iterative synthesis of oligo-PPV's has been described, [23][START_REF] Ono | A New Synthetic Method for Oligo(phenylenevinylenes) Terminated With Porphyrins[END_REF] but to the best of our knowledge, this reaction has never been applied to the synthesis of polyolefins starting from polysulfones. The synthetic approach we devise here opens a general and straightforward access to symmetrical PPV-like materials bearing identical aromatic fragments (Route A, Figure 1). By varying the nature of aryl groups, the optoelectronic properties could be tuned depending on the targeted application (OPV, OLED …). [START_REF] Roncali | Molecular Engineering of the Band-Gap of π-Conjugated Systems: Facing Technological Applications[END_REF][START_REF] Nalwa | Handbook of Organic Electronics and Photonics[END_REF] Furthermore, the conjunctive nature of the Ramberg-Bäcklund process should be particularly appealing for the design of alternating monomer units along the π-conjugated backbone (Route B, Figure 1). For example, it could allow the formation of "donor-acceptor" alternating low band gap copolymers, by using electron-rich and electron-poor monomer units. Such copolymers are characterized by an extended optical absorption to the red region, and allow for a better manipulation of the HOMO/LUMO levels, providing conjugated systems with relatively high charge carrier mobility. [START_REF] Ajayaghosh | Donor-Acceptor Type Low Band-Gap Polymers: Polysquaraines and Related Systems[END_REF][START_REF] Steckler | Very Low Band-Gap Thiadiazoloquinoxaline Donor-Acceptor Polymers as Multi-tool Conjugated Polymers[END_REF][START_REF] Xu | How to Design Low Band-Gap Polymers for Highly Efficient Organic Solar Cells[END_REF][START_REF] Bundgaard | Low Band-Gap Polymers for Organic Photovoltaics, Solar Energy Mat[END_REF][START_REF] Colladet | Low Band Gap Donor-Acceptor Conjugated Polymers toward Organic Solar Cells Applications[END_REF] Figure 1. Synthetic strategies toward poly(arylene vinylene)s (PPV's) based on the Ramberg-Bäcklund reaction.

As an example of the potentiality of these arylene-vinylene polymers, recently, Nomura and coll. have obtained PPV's with different end-groups by combining acyclic diene metathesis polymerization with Wittig-type couplings. [START_REF] Miyashita | Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig-type Couplings[END_REF][START_REF] Yamamoto | Synthesis of All-Trans High Molecular Weight Poly(N-alkylcarbazole-2,7-vinylene)s and Poly(9,9-dialkylfluorene-2,7-vinylene)s by Acyclic Diene Metathesis (ADMET) Polymerization Using Ruthenium-Carbene Complex Catalysts[END_REF] Here we describe the synthetic developments validating both strategies, by reporting the synthesis of poly(fluorene vinylene)-and poly(fluorene-carbazole vinylene)-type conjugated (co)polymers.

EXPERIMENTAL SECTION

All reactions were carried out under an argon atmosphere with solvents dried over activated alumina columns on MBraun Solvent Purification System (SPS-800), unless otherwise noted. All reagent-grade chemicals were obtained from commercial suppliers and were used as received, unless otherwise stated. [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF] H NMR and [START_REF] Meier | The Photochemistry of Stilbenoid Compounds and Their Role in Materials Technology Angew[END_REF] C NMR were recorded on various spectrometers: a Brüker Avance 300 ( 1 H: 300 MHz, 13 C: 75.46 MHz), a Brüker Avance 400 ( 1 H: 400 MHz, 13 C: 100.6 MHz) using CDCl3 as internal reference unless otherwise indicated. The chemical shifts (δ) and coupling constants (J) are expressed in ppm and Hz respectively. The following abbreviations were used to explain the multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, br = broad. FT-IR spectra were recorded on a Perkin-Elmer Spectrum 100 using a diamond ATR accessory. High-resolution mass spectra (HRMS) were recorded with a Waters QTOF 2 spectrometer in the electrospray ionization (ESI) mode. Melting points were not corrected and determined by using a Stuart Scientific SMP3 apparatus. Analytical thin layer chromatography was performed using silica gel 60 F254 pre-coated plates (Merck) with visualization by ultraviolet light, potassium permanganate. Flash chromatography was performed on silica gel (0.043-0.063 mm) with ethyl acetate (EtOAc) and petroleum ether (PE) as eluents unless otherwise indicated.

2,7-Bis(hydroxymethyl)-9,9'-dihexyl-9H-fluorene (2).

To a stirred solution of 9,9'-dihexyl-9Hfluorene-2,7-dicarbaldehyde 1 [START_REF] Paulsen | Tuning of HOMO Energy Levels and Open Circuit Voltages in Solar Cells Based on Statistical Copolymers Prepared by ADMET Polymerization[END_REF] (4.29 g, 11 mmol) in a 3:1 THF/MeOH mixture (100 mL), NaBH4 (3.34 g, 88 mmol) was added portion wise at 0 °C and then the reaction mixture was allowed to warm to room temperature for 4 h. The reaction was quenched with aq. NH4Cl solution (10 mL), and the aqueous layer extracted with ethyl acetate (2 x 50 mL). The organic layer was then dried over anhydrous Na2SO4 and solvents evaporated to give a crude mixture which was purified by flash column chromatography (silica, EtOAc/PET 1:9), affording the desired compound as a white solid (3.46 g, 80%). The spectral data are consistent with those reported in the literature. [START_REF] Jin | Design, Synthesis, and Electroluminescent Property of CN-Poly(dihexylfluorenevinylene) for LEDs[END_REF] Mp = 74-76 °C; IR (ATR) νmax (cm -1 ) : 3285, 2925, 2854, 1457; [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF]

2,7-Bis(bromomethyl)-9,9'-dihexyl-9H-fluorene (F-Br).

To a stirred solution of 2 (1.54 g, 3.91 mmol) in benzene (20 mL), PBr3 (1.09 mL, 11.7 mmol) was slowly added at room temperature, then the reaction mixture was heated to 45 °C for 6 h. The reaction was quenched with water (10 mL) and extracted with dichloromethane (2 x 25 mL). The organic layer was dried over anhydrous Na2SO4 and solvents evaporated to give a crude mixture which was purified by flash column chromatography (silica, CH2Cl2/PET 1:9) to afford the compound F-Br as a white solid (1.21 g, 59%). The spectral data are consistent with literature data. [START_REF] Jin | Design, Synthesis, and Electroluminescent Property of CN-Poly(dihexylfluorenevinylene) for LEDs[END_REF] Mp = 51-53 °C; IR (ATR) νmax (cm -1 ) : 2924, 1468, 1291; 1 H NMR (300 MHz, CDCl3): δ 0.53-0.68 (m, 4H), 0.70-0.82 (m, 6H), 0.95-1.18 (m, 12H), 1.90-2.02 (m, 4H), 4.59 (s, 4H), 7.32-7.39 (m, 4H), 7.59-7.68 (m, 2H); [START_REF] Meier | The Photochemistry of Stilbenoid Compounds and Their Role in Materials Technology Angew[END_REF] 2,7-Bis(mercaptomethyl)-9,9'-dihexyl-9H-fluorene (F-SH). Following a slightly modified literature procedure, [START_REF] Pechlivanidis | Paracyclophanes: Extending the Bridges. Synthesis[END_REF] to a stirred solution of F-Br (1.04 g, 2 mmol) in EtOH (10 mL), thiourea (0.334 g, 4.40 mmol) was added and the reaction mixture was heated to reflux for 4 h. Then, the solvent was evaporated under vacuum, the solid obtained was hydrolyzed with 50% aqueous sodium hydroxide solution (10 mL) and extracted with EtOAc (2 x 25 mL). The organic layer was dried over anhydrous Na2SO4, and solvents evaporated to give a crude mixture, which was purified by flash column chromatography (silica, CH2Cl2/PET 3:7) to afford the desired compound F-SHas a white solid (0.42 g, 49%). mp: 39-41°C; IR (ATR) νmax (cm -1 ) : 2925, 2556, 1520; 1 H NMR (300 MHz, CDCl3): δ 0.54-0.68 (m, 4H), 0.76 (t, 6H, J = 6.9 Hz), 0.95-1.18 (m, 12H), 1.77 (t, 2H, J = 7.5 Hz), 1.86-1.98 (m, 4H), 3.82 (d, 4H, J = 7.5 Hz), 7.22-7.30 (m, 4H), 7.54-7.62 (m, 2H); [START_REF] Meier | The Photochemistry of Stilbenoid Compounds and Their Role in Materials Technology Angew[END_REF]

Synthesis of PF-S.

In a sealed tube, a solution of F-Br (1.04 g, 2 mmol) and F-SH (0.85 g, 2 mmol) in a 1:1 THF/MeOH mixture (20 mL) was treated with powdered KOH (0.34 g, 6 mmol) and the reaction mixture was heated to 100 °C for 14 h. Then, the reaction mixture was cooled to room temperature and the solvent evaporated under vacuum. The crude reaction mixture was washed with H2O (20 mL), MeOH (20 mL) and the solid filtered. The latter was then dissolved in CHCl3 (5 mL) and purified by precipitation using MeOH (100 mL), to provide the desired compound (PF-S) as a pale yellow solid (1.27 g, 78%). IR (ATR) νmax (cm -1 ) : 2923, 2852, 1465, 817, 748; 1 H NMR (300 MHz, CDCl3): δ 0.52-0.83 (m, 10H), 0.90-1.21 (m, 12H), 1.88-2.12 (m, 4H), 3.68 (s, 4H), 7.19-7.35 (m, 4H), 7.56-7.70 (m, 2H); [START_REF] Meier | The Photochemistry of Stilbenoid Compounds and Their Role in Materials Technology Angew[END_REF]

Synthesis of PF-SO.

A stirred solution of PF-S (0.98 g, 2.5 mmol) in CHCl3 (50 mL) was treated with m-CPBA (2.16 g, 12.5 mmol) and the reaction mixture was stirred at room temperature for 8 h. Then the reaction mixture was filtered and washed with CHCl3. The filtrate was washed with saturated aqueous NaHCO3 (2 x 25 mL), brine and water respectively. The organic solvent was evaporated and the crude compound thus obtained was purified by precipitation in a large excess of cold MeOH from a CHCl3 solution, to afford the desired polymer as a brown solid (0.67 g, 63%). IR (ATR) νmax (cm PF-SO via the rongalite ® route. A mixture of F-Br (0.26 g, 0.5 mmol), rongalite ® (0.3 g, 2.5 mmol), K2CO3 (0.34 g, 2.5 mmol) and tetra-n-butylammonium bromide (TBAB) (0.08 g, 0.25 mmol) in DMF (2.5 mL) was stirred at room temperature for 3 days. Water (5 mL) was then added to the reaction mixture. The resulting solid was filtered and washed with water (10 mL) and MeOH (10 mL). The crude compound thus obtained was purified by precipitation in a large excess of cold MeOH from a CHCl3 solution, to obtain the PF-SO (0.078 g, 37%) as a white solid. The spectral data ( 1 H NMR) are consistent with the earlier data.

Synthesis of PFV.

In a sealed round bottom flask, a stirred solution of PF-SO (0.20 g, 0.47 mmol) in a 1:1 THF/t-BuOH mixture (10 mL) was treated with freshly prepared Al2O3-KOH (1 g) at 0 °C and then CF2Br2 (1 mL) was added at the same temperature. The reaction mixture was then stirred at room temperature for 24 h. The reaction mixture was filtered through celite and washed with CH2Cl2. The solvent was evaporated and the crude compound thus obtained was purified by precipitation in a large excess of cold MeOH from a CHCl3 solution, to afford the desired polymer as a yellow solid (89 mg, 53%). IR (ATR) νmax (cm -1 ): 2924, 2853, 1466, 1048, 790; [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF] 2,7-Diformyl-9-(tridecan-7-yl)-9H-carbazole (4). Following a slightly modified literature procedure, [START_REF] Kim | Novel 4,7dithien-2-yl-2,1,3-benzothiadiazole-based Conjugated Copolymers with Cyano group in Vinylene Unit for Photovoltaic Applications[END_REF] a stirred solution of 3 (5.07g, 10 mmol) in THF (50 mL) was cooled to -78 °C and a 1.85 M solution of n-BuLi in hexanes (11.4 mL, 21 mmol) was added and stirred at this temperature for 1 h. Then DMF (2.3 mL, 30 mmol) in THF (10 mL) was added dropwise and the reaction mixture was allowed to warm to room temperature and stirred for 1 h. The reaction mixture was quenched with aq. NH4Cl and extracted with EtOAc (2 x 50 mL). The organic layer was dried over anhydrous Na2SO4, and solvents evaporated to give a crude mixture, which was purified by column chromatography (silica gel, EtOAc/PET 1:9) to afford 4 as a yellow solid (

2,7-Bis(mercaptomethyl)-9-(tridecan-7-yl)-9H-carbazole (C-SH).

To a stirred solution of 4 (3.24 g, 8.0 mmol) in a 3:1 THF/MeOH mixture (60 mL), NaBH4 (2.43 g, 64 mmol) was added portion wise at 0 °C and the reaction mixture was allowed to warm to room temperature for 4 h. The reaction was quenched with aqueous NH4Cl solution (100 mL), extracted with EtOAc (2 x 100 mL) and the organic layer was dried over anhydrous Na2SO4. The solvent was then evaporated to afford the desired compound as a pale viscous liquid and used without further purification in the next step. To a stirred solution of the crude compound (2.96 g, 7.24 mmol) in benzene (30 mL), PBr3 (1.0 mL, 21.8 mmol) was slowly added at room temperature, then the reaction mixture was heated to 45 °C for 6 h. The reaction was quenched with water (25 mL) and extracted with CH2Cl2 (2 x 50 mL). The organic layer was dried over anhydrous Na2SO4 and the solvent evaporated. The oily residue, 2,7-bis(bromomethyl)-9-(tridecan-7-yl)-9H-carbazole 5 was used in the next step without purification, since the compound was unstable under ambient condition. To a stirred solution of 5 (3.5 g, 6.5 mmol) in EtOH (30 mL) thiourea (1.5 g, 19.5 mmol) was added and the reaction mixture heated to reflux for 8 h. Then, the solvent was evaporated under vacuum, the solid obtained was hydrolyzed with 50% aqueous sodium hydroxide and extracted with EtOAc (2 x 50 mL). The organic layer was dried over anhydrous Na2SO4, and solvents evaporated to give a crude mixture, which was purified by flash column chromatography (silica, CH2Cl2/PET 3:7) to afford C-SH as a colorless liquid (1.56 g, 55%). The overall yield for the three steps is 47%. IR (ATR) νmax (cm -1 ): 2923, 2853, 2561, 1457, 1435; 1 H NMR (300 MHz, CDCl3): δ 0.78 (t, 6H, J = 6.6 Hz), 0.91-1.31 (m, 16H), 1.84 (t, 2H, J = 7.5 Hz),

Synthesis of PFC-S.

In a sealed tube, a solution of F-Br (0.52 g, 1 mmol) and C-SH (0.44 g, 1 mmol) in a 1:1 THF/MeOH mixture (10 mL) was treated with powdered KOH (0.17 g, 3 mmol) and the reaction mixture was heated to 100 °C for 14 h. Then, the reaction mixture was cooled to room temperature and the solvent evaporated under vacuum. The crude reaction mixture was washed with H2O and MeOH and the solid filtered. The latter was then dissolved in CHCl3 (5 mL) and purified by precipitation using MeOH (100 mL) to provide the desired compound (PFCS) as a pale yellow solid (0.62 g, 83%). IR (ATR) νmax (cm -1 ): 2922, 2849, 2354, 1599, 1440; [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF]

Synthesis of PFC-SO:

A stirred solution of PFC-S (0.54 g, 0.73 mmol) in CHCl3 (15 mL) was treated with m-CPBA (0.63 g, 3.6 mmol) and the reaction mixture was stirred at room temperature for 8 h. Then, the reaction mixture was filtered and washed with CHCl3. The filtrate was washed with saturated aqueous NaHCO3 (2 x 25 mL), brine and water respectively. The organic solvent was evaporated and the crude material thus obtained was purified by precipitation in a large excess of cold MeOH from a CHCl3 solution, to afford the desired polymer as a dark-green solid (0.43 g, 76%). IR (ATR) νmax (cm -1 ): 2930, 2823, 1480, 1308, 1110; [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF]

Synthesis of PFVCV.

In a sealed round bottom flask, a stirred solution of PFC-SO (0.2 g, 0.26 mmol) in a 2:1 THF/t-BuOH mixture (12 mL) was treated with freshly prepared Al2O3-KOH (0.3 g) at 0 °C, then CF2Br2 (1.5 mL) was added at the same temperature. The reaction mixture was stirred at room temperature for 24 h, then filtered through celite and washed with CH2Cl2. The solvent was evaporated and the crude material purified by precipitation in a large excess of cold MeOH from a CHCl3 solution, to afford the desired polymer as a yellow solid (32 mg, 43%). IR (ATR) νmax (cm -1 ): 2924, 2853, 1466, 1048, 790; [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF]

RESULTS AND DISCUSSION

Synthesis and characterization of symmetrical poly(arylene vinylene)s. For our initial studies, we have selected specific monomers, namely, 2,7-bis(bromomethyl)-9,9'-dihexyl-9H-fluorene (F-Br) and 2,7-bis(mercaptomethyl)-9,9'-dihexyl-9H-fluorene (F-SH) (Scheme 1). The general synthetic strategy to symmetrical PPV's following Route A is outlined in Figure 1. 9,9-Dihexylfluorene has been widely employed as a building block for the synthesis of electroluminescent polymers. [START_REF] Jin | Synthesis and Electroluminescence Properties of Poly(9,9-di-n-octylfluorenyl-2,7-vinylene) Derivatives for Light-Emitting Display[END_REF][START_REF] Sohn | Synthesis and Luminescence Properties of Poly[2-(9,9-dihexylfluorene-2-yl)-1,4-phenylenevinylene] and Its Copolymers Containing 2-(2-Ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene Units[END_REF][START_REF] Pei | The Synthesis and Characterization of an Efficient Green Electroluminescent Conjugated Polymer: Poly[2,7-bis(4-hexylthienyl)-9,9dihexylfluorene[END_REF] Moreover, fluorene-based polymers exhibit excellent solubility, good charge carrier mobility, and high solid state photoluminescence (PL) quantum yield. [START_REF] Leclerc | Polyfluorenes: Twenty years of Progress[END_REF] Reduction of fluorene-dicarbaldehyde [START_REF] Paulsen | Tuning of HOMO Energy Levels and Open Circuit Voltages in Solar Cells Based on Statistical Copolymers Prepared by ADMET Polymerization[END_REF] (1) with NaBH4 in THF/MeOH 42 afforded the 2,7-bis(hydroxymethyl)-9,9'-dihexyl-9H-fluorene (2) in 80% yield. Treatment of 2 with PBr3 in benzene [START_REF] Jin | Design, Synthesis, and Electroluminescent Property of CN-Poly(dihexylfluorenevinylene) for LEDs[END_REF] at 45 °C gave the desired 2,7-bis(bromomethyl)-9,9'-dihexyl-9Hfluorene monomer (F-Br) in 59% yield. Subsequent treatment of monomer F-Br with thiourea in refluxing EtOH for 4h followed by basic hydrolysis provided the desired monomer, F-SH (Scheme 1). [START_REF] Pechlivanidis | Paracyclophanes: Extending the Bridges. Synthesis[END_REF] Scheme 1. Synthesis of monomers 2,7-Bis(bromomethyl)-9,9'-dihexyl-9H-fluorene (F-Br) and 2,7-Bis(mercaptomethyl)-9,9'-dihexyl-9H-fluorene (F-SH).

The general protocol for the preparation of poly(fluorene vinylene) (PFV) is illustrated in Scheme 2.

After screening various conditions for the step-growth polymerization of stoichiometric amounts of F-Br and F-SH (see ESI, Tables S1-4), soluble polymers of rather high apparent molecular weight were obtained in presence of 3 eq. of powdered KOH in THF/MeOH (1:1) at 100 °C for 14 h. These conditions led to poly(fluorene-sulfide)s (PF-S) in 78% final yield. Strong, non-nucleophilic 1,1,3,3tetramethylguanidine (TMG) afforded higher molecular weights and narrower dispersities (see ESI). Due to their lower molecular weight, however, polymers obtained from KOH also proved more soluble. Initial studies on the oxidation of PF-S using oxone ® as the oxidizing agent in MeOH/H2O were unsuccessful, resulting in a mixture of sulfoxide and sulfone products. In contrast, treatment of 1 eq. of PF-S with 5 eq. of m-CPBA in CHCl3 at room temperature for 8 h afforded the polyfluorene-sulfone (PF-SO) in 63 % yield. The latter polymer was finally subjected to the Ramberg-Bäcklund reaction using Chan's modified procedure (CF2Br2, Al2O3-KOH, t-BuOH). [START_REF] Chan | A New one-flask Ramberg-Bäcklund Reaction[END_REF] The reaction was however sluggish under these conditions, very likely because of the low solubility of PF-SO in t-BuOH. We noted that a mixture of THF and t-BuOH (1:1) was more suitable for this reaction. Treatment of PF-SO with an excess of CF2Br2 and freshly prepared Al2O3-KOH in THF/t-BuOH (1:1), at room temperature for 24 h, thus gave polymer PFV in 53% yield. The three polymers, PF-S, PF-SO and PFV were purified by precipitation using CHCl3 and MeOH at room temperature.

Scheme 2. Synthesis of poly(fluorene vinylene) (PFV) via a three-step procedure involving stepgrowth polymerization, oxidation and Ramberg-Bäcklund reaction. Characterization of the monomers and related polymers (PF-S, PF-SO, PFV) through IR and 1 H NMR spectroscopies, revealed the expected structures with high purity (Figure 2). The overlay of IR spectra of the different polymers is shown in Figure S1 (ESI). Comparison between IR spectra of PF-S and PF-SO showed additional absorption bands at 1319, 1100 cm -1 , corresponding to the S=O group. During post-functionalization of PF-SO into PFV, disappearance of the band at 1319 cm -1 and a new absorption band at 860 cm -1 due to the olefinic moiety was observed, confirming the complete transformation of the sulfone group. [START_REF] Wang | Semiconducting π-Conjugated Systems in Field-Effect Transistors: A Material Odyssey of Organic Electronics[END_REF] H NMR spectra revealed the presence of methylene protons for monomers F-Br and F-SH appearing at δ 4.59 (s) and 3.82 (d) ppm, respectively. These signals vanished in the spectrum of PF-S, where a single peak at δ 3.68 ppm (Figure 2) was noted. Upon oxidation, the methylene protons of PF-SO were shifted downfield to δ 4.20 ppm. Importantly, no signal around δ 3.90 ppm, resulting from a partial oxidation of the sulfide into the sulfoxide was detected. [START_REF] Burdon | Sulfoxide-carbodiimide Reactions. IV. Acid-catalyzed Reactions of Phenols with Sulfoxides and Carbodiimides[END_REF] After treating the PF-SO under modified Ramberg-Bäcklund reaction conditions, 1 H NMR of PFV revealed a (E)stereoselectivity for the double bonds, a result consistent with observations made for model dibenzylic sulfones reported earlier, [START_REF] Chan | A New one-flask Ramberg-Bäcklund Reaction[END_REF][START_REF] Sӧderman | 1,2-Dibromotetrachloroethane: An Ozone-Friendly Reagent for the in-Situ Ramberg-Bäcklund Rearrangement and Its Use in the Formal Synthesis of E-Resveratrol[END_REF] and that is in good agreement with spectroscopic data reported by Nomura et al. concerning PFV synthesis by ADMET. [START_REF] Miyashita | Synthesis of Poly(arylene vinylene)s with Different End Groups by Combining Acyclic Diene Metathesis Polymerization with Wittig-type Couplings[END_REF][START_REF] Yamamoto | Synthesis of All-Trans High Molecular Weight Poly(N-alkylcarbazole-2,7-vinylene)s and Poly(9,9-dialkylfluorene-2,7-vinylene)s by Acyclic Diene Metathesis (ADMET) Polymerization Using Ruthenium-Carbene Complex Catalysts[END_REF] It is also worth mentioning that we did not observe any residual benzylic protons at δ 4.20 ppm, attesting to the complete conversion of dibenzylic sulfones into olefinic moieties, and to the formation of fully -conjugated polymers. Average molecular weights were evaluated by size exclusion chromatography (SEC) in THF using polystyrene standards. Results are summarized in Table 1 and SEC traces of PFV, PF-S and PF-SO are shown in Figure 3. The fluorenebased copolymer, PF-S, is characterized by a moderate molecular weight for the parent compounds (Table 1, entry 1), increasing after sulfonation (Table 1, entry 2). The final polymer, PFV, has a similar molecular weight than its precursor PF-S (Table 1, entry 3). After post-chemical modification forming the sulfone and the -conjugated polymers, Mn and Mw values changed significantly, most likely owing to the variation of solubility of the different polymers. Finally, the high thermal stability of the different polymers (PF-S, PF-SO, PFV) was established by TGA with a loss less than 10% upon heating up to 400 °C (see Figure S6, ESI).

Synthesis of poly(fluorene-sulfone)s (PF-SO) via the Rongalite ® route (see Scheme 3).

With a view at developing a simpler and inexpensive protocol for the synthesis of polysulfone-type precursors of the Ramberg-Bäcklund reaction, we envisioned that commercially available rongalite ® , [START_REF] Kotha | Rongalite: A Useful Reagent in Organic Synthesis[END_REF] i.e. sodium hydroxymethanesulfinate, could serve as a source of sulfoxylate dianion (SO2 2-). Rongalite ® is inexpensive and is used as a less oxygen-sensitive bleaching agent than sodium dithionite (Na2S2O4), for the synthesis of symmetrical sulfones. Best results were obtained when treated 1 eq. of fluorene-Br (F-Br) with rongalite ® (5 eq.) in the presence of K2CO3 (5 eq.) tetra-n-butylammonium bromide (TBAB) (0.5 eq.) as a phase-transfer catalyst in DMF at room temperature for 3 days (Scheme 3). This gave the desired polyfluorene-sulfone (PF-SO) with 𝑀 ̅ n = 2700 g/mol and Ð = 1.7. Despite a modest isolated yield of 37%, and low molecular weight, this method opens up an easy entry to PF-SO, and its application affords an access to symmetrical PPV-like materials in only two-step from readily available benzylic bromides.

Scheme 3. An access to PF-SO using the rongalite ® route.

Synthesis of unsymmetrical poly(arylene vinylene)s. Based on the above findings, we extended our strategy to the synthesis of unsymmetrical poly(arylene vinylene)s (PAr 1,2 V's; route B, Figure 1). A dithiol-functionalized carbazole derivative (C-SH) was thus selected as a co-monomer, the latter being synthesized as shown in Scheme 4. [START_REF] Kim | Novel 4,7dithien-2-yl-2,1,3-benzothiadiazole-based Conjugated Copolymers with Cyano group in Vinylene Unit for Photovoltaic Applications[END_REF] Compound 5 being not stable at room temperature, the crude compound was used in the next step without further purification, leading to the desired C-SH in 55% yield, after treatment with thiourea and hydrolysis under basic conditions.

Scheme 4. Synthesis of carbazole monomer C-SH.

To validate our strategy for the synthesis of alternated poly(arylene vinylene)s (Route B, Figure 1), 1 eq. of F-Br was treated with 1 eq. of C-SH in the presence of 3 eq. of powdered KOH in THF/MeOH at 100 °C for 14 h (Scheme 5). This gave a polysulfide, PFC-S, in 83% yield after purification. Oxidation of PFC-S with 5 eq. of m-CPBA in CHCl3 at room temperature for 8 h provided the corresponding polysulfone (PFC-SO) in 76% yield. Finally, treatment of PFC-SO under Ramberg-Bäcklund conditions produced the desired poly(fluorene vinylene-co-carbazole vinylene) (PFVCV) in 43% yield. Monomers and polymers (PFC-S, PFC-SO and PFVCV) were characterized by SEC, IR and 1 H NMR spectroscopy. Similar patterns were observed by 1 H NMR, as illustrated in Figure 4. Polysulfides PFC-S exhibited high apparent molecular weights (Table 1, entries 4-6). Again, this could be due to an increase of the hydrodynamic volume in THF after sulfonation. Higher molecular weights were achieved for the parent PVCS (Table 1, entry 4), but lower values were noted after the two modification steps forming PFC-SO and PFVCV (Table 1, entries 5-6), respectively (see SEC traces in Figure 5). This could not only be explained by a different solution behavior, but also by possible fractionation during purification by filtration, in agreement with the decrease in dispersity. As above for PFV, high thermal stability of the polymers (PFC-S, PFC-SO and PFVCV) was shown by TGA (see Figure S6, ESI). Overall, this three-step reaction sequence to poly(arylene vinylene)s is efficient and stereoselective, although the Ramberg-Bäcklund reaction step gives moderate yields, particularly when steric hindrance around the olefinic moiety is increasing. This limitation is likely inherent to the Ramberg-Bäcklund reaction, which proceeds through an episulfone intermediate resulting from the displacement of the halogen ' to the sulfonyl group by an -carbanion (Scheme 6). This process is believed to occur through a semi-W-conformation, the elimination step being rate-limiting. [START_REF] Paquette | The Base-induced Rearrangement of α-Halo Sulfones[END_REF][START_REF] Meyers | 2,4-Pentadienyl)trimethylsilane: a Useful Pentadienylation Reagent[END_REF] While this conformation is easily attained in small acyclic systems, this might not be the case with polymeric chains, in which strain and folding might retard the elimination and the subsequent SO2 extrusion. This might also explain the long reaction time needed in our polymerization experiments, compared to those noted with molecular compounds, and the low conversion with substrates having substituents on the arenes ortho to the sulfonyl chain (not described here). Scheme 6. Conformational requirements in the Ramberg-Bäcklund reaction.

Optical properties. The optical properties of the final (co)polymers were analyzed by UV-Vis absorption and fluorescence spectrophotometry (PFV, PFVCV) both in solution in chloroform and in bulk on solid thin films. UV-Vis in chloroform are shown for PFV (and its precursors PF-S and PF-SO) on Figure 6, and for for PFVCV (and its precursors PFC-S and PFC-SO) on Figure 7. In both cases, a strong red-shift for the two final (co)polymers can be observed. It can be attributed to the extension of the conjugation for PFV and PFVCV, while their precursors are not π-conjugated. Surprisingly, the two (co)polymers, PFV and PFVCV showed almost the same UV-Vis pattern in chloroform solution (Figures 6 and7), exhibiting in both cases two absorption maxima around 425 and 455 nm in solution. These UV data are very similar to those of PFV synthesized by the ADMET method, as reported by Namura et al. [START_REF] Yamamoto | Synthesis of All-Trans High Molecular Weight Poly(N-alkylcarbazole-2,7-vinylene)s and Poly(9,9-dialkylfluorene-2,7-vinylene)s by Acyclic Diene Metathesis (ADMET) Polymerization Using Ruthenium-Carbene Complex Catalysts[END_REF] In other words, alternation with carbazole subunits did not affect optical properties of the material. No significant change was eventually noted in the UV-Vis absorption from thin-films of (co)polymers PFV & PFVCV (See ESI, Figure S5). The absorption bands were slightly red-shifted relative to that of PFV derivatives. [START_REF] Jin | Poly(fluorenevinylene) Derivative by Gilch Polymerization for Light-Emitting Diode Applications[END_REF] Such small differences can be assigned to the effect of alkyl chains from fluorene repeating units that are shorter in our case, thus favoring  stacking and extension of conjugation length. The optical band gaps (Eg) for both polymers, calculated from the onset of the absorption, were approximately 2.6 eV. Figures 8 and9 shows the fluorescence spectra recorded with the excitation wavelength corresponding to the two maxima of absorption of the polymers at 425 and 450 nm. In solution, two maxima are observed for both polymers (as well as a slight shoulder) and the corresponding wavelengths are slightly dependent on the wavelength of excitation. For instance, a PFV excitation at 425 nm (Figure 8(a)) led to a strong emission band at 463 nm, then a shoulder at 494 nm and a slight shoulder at 534 nm in excellent agreement with Nomura's emission spectrum recorded at 426 nm (465, 496 and 530 nm respectively). [START_REF] Yamamoto | Synthesis of All-Trans High Molecular Weight Poly(N-alkylcarbazole-2,7-vinylene)s and Poly(9,9-dialkylfluorene-2,7-vinylene)s by Acyclic Diene Metathesis (ADMET) Polymerization Using Ruthenium-Carbene Complex Catalysts[END_REF] However, solid state, broad emission peaks can be observed for both, in almost all the visible region and whatever the wavelength of excitation. In solution, both polymer exhibit two maxima of emission at 475 nm and 500 nm. When excited at 450 nm (Figures 8(b) and 9(b)), the second emission peak was more prominent than when excitation was performed at 425 nm (Figures 8(a) and 9(a)). In solid thin films, both polymers (PFV and PFVCV) exhibited a broad emission band, even when they were excited at 425 nm (Figures 8(c) and 9(c)) or at 450 nm (Figures 8(b) and 9(b)). However, two main differences can be highlighted between PFV and PFVCV emission spectra in thin film. First, a more prominent emission peak was noted around 512 nm for PFVCV (Figure 9 (c) and 9 (d)), in agreement with reported data on poly(carbazolyl-2,7-vinylene), which is characteristic of a more blueish emitted light as compared to greenish-blue emitted light from PFV. [START_REF] Song | Synthesis and Characterization of Poly(carbazolyl-2,7-vinylene) Derivatives for Organic Light-emitting Diode Applications[END_REF] Secondly, the emission band was extended up to 700 nm in the case of PFV, compared to 650 nm for PFVCV, emphasizing the impact of the carbazolyl vinylene group insertion. This strongest red-shift in solid state for PFV could also be explained by a better organization (e.g.  stacking) comparing to PFVCV. Finally, the quantum yield of the purified PFV material, measured upon excitation at 400 nm in THF, reached 40.3% (ESI). Although lower than those found by Nomura et al., [START_REF] Yamamoto | Synthesis of All-Trans High Molecular Weight Poly(N-alkylcarbazole-2,7-vinylene)s and Poly(9,9-dialkylfluorene-2,7-vinylene)s by Acyclic Diene Metathesis (ADMET) Polymerization Using Ruthenium-Carbene Complex Catalysts[END_REF] our values are very satisfactory, indicating that the PFV prepared through our method is also free of defects, as further supported by the similar absorption and emission maxima (vide supra). Thermal stability. The thermal stability of PFV and its precursors (PF-S, PF-SO) as well as the stability of PFVCV were finally analyzed by TGA (See ESI, Figure S6). The two conjugated polymers PFV and PFVCV are stable until 450 °C. Their precursors (of sulfide-and sulfone-type) are reacting at lower temperatures (between 300 °C and 350 °C) and finally start to decompose at 450 °C.

CONCLUSION

A novel synthetic strategy involving a sulfone-based precursor step-growth polymerization route followed by post-chemical modification via the Ramberg-Bäcklund reaction provides an easy access to poly(arylene vinylene)-like semiconductors. The sulfone precursors are easily obtained allowing the connection between electronically differentiated arenes. Symmetrical polysulfones may also be elaborated starting from benzylic bromides precursors and rongalite ® as a source of sulfoxylate dianion (SO2 2-). Polysulfones and their polysulfide precursors can be equipped with apolar alkyl chains, thus securing their solubility in organic solvents during polymer elaboration, allowing the final purification of the material through precipitation. Further optimization may be needed, in particular to reduce the environmental impact of the reaction sequence. However, such a methodology used to synthesize copolymers composed of carbazolyl and fluorenyl subunits paves the way for the preparation of a plethora of copolymer structures and/or various architectures. We are for instance currently investigating alternation of electron-rich and electron-poor subunits, along with the integration of such materials free of transition metal sources in optoelectronic devices.

  H NMR (300 MHz, CDCl3): δ 0.71-0.83 (m, 8H), 0.94-1.21 (m, 14H), 1.89-2.15 (m, 4H), 7.30 (s, 2H), 7.48-7.63 (m, 4H), 7.70 (d, 2H, J = 7.8 Hz); λmax: 426, 450 nm.

Figure 2 .

 2 Figure 2. 1 H NMR spectra of (i) PFV; (ii) PF-SO2; (iii) PF-S; (iv) F-SH; (v) F-Br in CDCl3 (400 MHz); n-hexyl peaks are omitted for clarity.

Figure 3 .

 3 Figure 3. SEC traces in THF (PS standards; RI Detector) of PFV, PF-SO and PF-S.

Scheme 5 .

 5 Scheme 5. Synthesis of poly(fluorene vinylene-co-carbazole vinylene) PFVCV.

Figure 4 . 1 H

 41 Figure 4. 1 H NMR spectra of (i) PFCV; (ii) PFC-SO; (iii) PFC-S; (iv) C-SH; (v) F-Br in CDCl3 (400 MHz); The n-hexyl peaks are omitted for clarity.

Figure 5 .

 5 Figure 5. SEC traces in THF of PFVCV, PFC-SO and PFC-S.

Figure 6 .Figure 7 .

 67 Figure 6. UV-vis absorption of PF-S, PF-SO and PFV

Figure 8 .Figure 9 .

 89 Figure 8. Emission spectra of PFV: (a) excited at 425 nm in CHCl3; (b) excited at 450 nm in CHCl3; (c) excited at 420 nm on thin film; (d) excited at 450 nm on thin-film.

  C NMR (75 MHz, CDCl3): δ 13.98, 22.46, 23.61, 29.51, 31.34, 34.43, 40.05, 55.11, 120.03, 123.64, 127.98, 136.86, 140.71, 151.63; HRMS: Calcd. for C27H36Br2 [M] +. 518.11838, found 518.12470.

  C NMR (75 MHz, CDCl3): δ 13.98, 22.49, 23.64, 29.37, 29.57, 31.37, 40.15, 54.95, 119.63, 122.48, 126.69, 139.69, 139.91, 151.34; HRMS: Calcd. for C27H38S2 [M] +. 426.24149, found 426.24213.

  C NMR (75 MHz, CDCl3): δ 13.98, 22.52, 23.82, 29.74, 31.56, 35.50, 40.54, 54.96, 119.56, 123.42, 127.89, 136.84, 139.87, 150.97; λmax: 290, 316 nm.

  -1 ): 2924, 2853, 1467, 1316, 1150, 612; 1 H NMR (300 MHz, CDCl3): δ 0.57-0.77 (m, 10H), 0.95-1.15 (m, 12H), 1.96-2.13 (m, 4H), 4.20 (s, 4H), 7.35 (d, 2H, J = 7.8 Hz), 7.44 (s, 2H), 7.76 (d, 2H, J = 7.8 Hz); 13 C NMR (75 MHz, CDCl3): δ 13.93, 22.46, 23.91, 29.62, 31.50, 40.24, 55.40, 58.18, 120.43, 125.37, 126.70, 129.89, 141.15, 151.67; λmax: 290, 316 nm.

  3.26 g, 81%). Mp = 88-90 °C; IR (ATR) νmax (cm -1 ): 2917, 2850, 1676, 1227; 1 H NMR (300 MHz, CDCl3): δ 0.76 (t, 6H, J = 6.6 Hz), 0.89-0.92 (m, 2H), 1.04-1.34 (m, 14H), 1.95-2.12 (m, 2H), 2.24-2.42 (m, 2H), 4.72 (septet, 1H, J = 5.1 Hz), 7.80 (d, 2H, J = 7.8 Hz), 8.03 (s, 1H), 8.16 (s, 1H), 8.23-8.37 (m, 2H); 13 C NMR (75 MHz, CDCl3): δ 13.88, 22.38, 26.73, 28.90, 31.44, 33.75, 57.37, 110.48, 113.14, 121.08, 121.87, 126.40, 135.21, 143.24, 192.42; HRMS: Calcd. for C27H35NO2 [M] +. 405.26678, found 405.26691.

  1.87-1.98 (m, 2H), 2.18-2.35 (m, 2H), 3.94 (d, 4H, J = 7.5 Hz), 4.53 (septet, 1H, J = 5.1 Hz), 7.16 (d, 2H, J = 7.8 Hz), 7.34 (s, 1H), 7.50 (s, 1H), 7.91-8.06 (m, 2H); 13 C NMR (75 MHz, CDCl3): δ 14.05, 22.58, 26.77, 29.09, 30.02, 31.60, 33.70, 56.35, 108.25, 110.95, 119.00, 120.21, 120.44, 121.36, 138.21, 138.68; HRMS: Calcd. for C27H39NS2 [M] +. 441.25239, found 441.25219.

  H NMR (400 MHz, CDCl3): δ 0.57-0.80 (m, 16H), 0.92-1.32 (m, 28H), 1.88-2.08 (m, 6H), 2.25-2.44 (m, 2H), 3.71 (s, 4H), 3.80 (s, 4H), 4.52-4.67 (m, 1H), 7.07-7.16 (m, 2H), 7.21-7.32 (m, 4H), 7.40 (s, 1H), 7.57 (s, 1H), 7.63 (d, 2H, J = 7.8 Hz), (t, 2H, J = 8.7 Hz); 13 C NMR (100 MHz, CDCl3): δ 13.96, 22.52, 23.82, 26.85, 29.14, 29.74, 31.54, 31.60, 33.83, 35.84, 36.24, 40.48, 54.96, 56.39, 109.11, 111.78, 119.50, 119.83, 120.08, 121.36, 122.73, 123.49, 127.89, 135.18, 135.58, 136.97, 139.13, 139.87, 142.55, 151.04; λmax: 245, 276, 317 nm.

Table 1 .

 1 Size exclusion Chromatography (SEC) analysis of polymers in THF at 25 °C using PS standards

	for calibration
	entry	polymer	𝑀 ̅ n (a) (g/mol)	𝑀 ̅ w (a) (g/mol)	Ð (a)
	1	PF-S	7,500	14,300 1.90
	2	PF-SO	15,000	32,000 2.10
	3	PFV	7,600	13,200 1.70
	4	PFC-S	40,700	82,300 2.02
	5	PFC-SO	30,400	61,200 2.01
	6	PFVCV	5,500	11,400 2.05
	(a) Number-and weight-average molar mass (in g.mol -1 ) and
	dispersity determined by size exclusion chromatography in
	THF (PS calibration).