Synthesis, molecular and morphological characterization of complex architecture conductive polymers

In this dissertation the synthesis of conductive polymers with complex architecture and their molecular and morphological characterization are presented. The synthesis of copolymers comprised of polythiophene with other polymers, such us polystyrene, has shown that the solubility is increased considerably without degradating its conductivity. Poly(2-vinylthiophene) is potentially a very useful precursor polymer for the production of soluble conductive polythiophenes due to the thiophene ring existence in the monomer unit. After the study of the free radical polymerization (FRP) and nitroxide mediated free radical polymerization (SFRP) of the 2-vinylthiophene monomer, grafted copolymers of poly(2-vinylthiophene) and polythiophene (P2VT-g-PT) were prepared by adopting the chemical oxidative polymerization of thiophene with iron trichloride (FeCl3). Aditionally, a diblock copolymer precursor of the PS-b-P2VT type was synthesized via SFRP in order to prepare a terpolymer with the poly(2-vinylthiophene) block grafted with polythiophene [PS-b-(P2VT-g-PT)]. Also, the synthesis of diblock copolymers of polystyrene and polythiophene is accomplished via anionic polymerization techniques under high vacuum for the PS block and sequential chemical oxidative polymerization with FeCl3 for the preparation of PT. Molecular characterization was accomplished via size exclusion chromatography, vapor pressure osmometry, proton and carbon nuclear magnetic resonance spectroscopy, infrared spectroscopy and consequently morphological characterization was completed via scanning electron microscopy and atomic force microscopy. The thermal behavior of all samples was studied using differential scanning calorimetry and thermogravimetric analysis experiments. The molecular characterization results verified the successful synthesis and moreover, confirmed the production of a non-linear grafted copolymer of PS with one branch of PT [(PS)2PT] along with the synthesis of the linear PS-b-PT copolymer. The microscopy images confirmed morphologically the presence of polythiophene in all samples forming the expected ‘cauliflower’ stuctures.Στην παρούσα διδακτορική διατριβή παρουσιάζεται η σύνθεση αγώγιμων πολυμερών πολύπλοκης αρχιτεκτονικής, ο μοριακός και μορφολογικός χαρακτηρισμός τους. Η σύνθεση συμπολυμερών του πολυ(θειοφαινίου) με άλλα πολυμερή έχει αποδειχτεί πως αυξάνει αρκετά τη διαλυτότητά του χωρίς να υποοβαθμίζει σημαντικά τις αγώγιμες ιδιότητές του. Το πολυ(2-βινυλοθειοφαίνιο) αποτελεί ένα εν δυνάμει αρκετά χρήσιμο πρόδρομο πολυμερές για τη σύνθεση διαλυτών αγώγιμων πολυμερών πολυ(θειοφαινίου) εξαιτίας του θειοφαινολικού δακτυλίου που περιέχεται στο μονομερές. Μετά τη μελέτη του ελεύθερου ριζικού πολυμερισμού του μονομερούς 2-βινυλοθειοφαινίου με ή χωρίς τη χρήση νιτροξειδίων (FRP/SFRP), προέκυψαν εμβολιασμένα συμπολυμερή του πολυ(2-βινυλοθειοφαινίου) και του πολυ(θειοφαινίου) (P2VT-g-PT) με χρήση του χημικού οξειδωτικού πολυμερισμού του θειοφαινίου με τριχλωριούχο σίδηρο (FeCl3). Επιπλέον, συντέθηκε ένα πρόδρομο συμπολυμερές κατά συστάδες πολυστυρενίου και πολυ(2-βινυλοθειοφαινίου) (PS-b-P2VT) με SFRP ώστε να προκύψει τελικά το τριπολυμερές κατά συστάδες πολυστυρενίου και πολυ(2-βινυλοθειοφαινίου) εμβολιασμένου με πολυ(θειοφαίνιο) [PS-b-(P2VT-g-PT)]. Επίσης, συντέθηκαν δισυσταδικά συμπολυμερή πολυστυρενίου και πολυ(θειοφαινίου) με συνδυασμό της τεχνικής του ανιοντικού πολυμερισμού υπό υψηλό κενό για το PS και του χημικού οξειδωτικού πολυμερισμού με FeCl3 για το ΡΤ. Ο μοριακός χαρακτηρισμός πραγματοποιήθηκε με χρωματογραφία αποκλεισμού μεγεθών, ωσμωμετρία τάσης ατμών, φασματοσκοπία πυρηνικού μαγνητικού συντονισμού πρωτονίου και άνθρακα, φασματοσκοπία υπερύθρου και ο μορφολογικός χαρακτηρισμός πραγματοποιήθηκε με ηλεκτρονική μικροσκοπία σάρωσης και μικροσκοπία ατομικής δύναμης. Η θερμική συμπεριφορά όλων των δειγμάτων μελετήθηκε με διαφορική θερμιδομετρία σάρωσης και θερμοβαρυμετρική ανάλυση. Από το μοριακό χαρακτηρισμό προέκυψε πως η σύνθεση όλων των δειγμάτων είναι επιτυχής και επιπροσθέτως πως η σύνθεση των συμπολυμερών πολυστυρενίου με το πολυ(θειοφαίνιο) οδηγεί εκτός από το γραμμικό δισυσταδικό συμπολυμερές (PS-b-PT) και σε μη γραμμικό διακλαδισμένο συμπολυμερές με ένα κλάδο PT [(PS)2PT]. Ο χαρακτηρισμός όλων των δειγμάτων με μικροσκοπία επιβεβαίωσε και μορφολογικά την παρουσία του πολυ(θειοφαινίου) στα δείγματα με τη μορφή δομών τύπου ‘κουνουπιδιού’

Synthesis and molecular characterization of polythiophene block Co-, ter-polymers and four-arm star homopolymer

We report the synthesis of polythiophene (PT) block copolymers with polystyrene (PS) or polyisoprene of increased 3,4 microstructure (PI3,4) and triblock terpolymer of the PS-b-PI-b-PT type. Tetrathienylsilane (C16H12S4Si) was also prepared in order to react with thiophene and eventually synthesize a four-arm star PT homopolymer. The preparation of the functional precursors and intermediate products (PS, PI, PS-b-PI3,4, and C16H12S4Si) was achieved through high vacuum techniques, and PT was synthesized under ambient conditions via the corresponding chemical oxidative polymerization reaction. The final polymers and the intermediate precursors were molecularly characterized by size exclusion chromatography (SEC), membrane osmometry (MO), proton nuclear magnetic resonance (1H-NMR), and carbon nuclear magnetic resonance (13C-NMR) spectroscopies

Post-functionalization of polyvinylcarbazoles: An open route towards hole transporting materials for perovskite solar cells

We report on the potential of tuning poly(9-vinylcarbazole) (PVK) properties through functionalization for an application as hole transport material (HTM) for perovskite solar cells (PSCs). The synthesized PVK-based polymers were substituted with moieties of interest to improve the solubility, the charge transport properties, or to tune energy levels. Bis(4-methoxyphenyl)amine moieties were found to improve the hole mobility and to increase the HOMO level of the PVK. Therefore, PSCs employing PVK-[N(PhOCH3)2]2 as HTM exhibited a best PCE of 16.7%. Compared to spiro-OMeTAD, first studies have shown that PVK-[N(PhOCH3)2]2 could extend PSC lifetime

Structure/Properties Relationship of Anionically Synthesized Diblock Copolymers “Grafted to” Chemically Modified Graphene

International audiencenovel approach to obtaining nanocomposite materials using anionic sequential polymerization and post-synthetic esterification reactions with chemically modified graphene sheets (CMGs) is reported. The anionically synthesized diblock copolymer precursors of the PS-b-PI-OH type were grafted to the chemically modified –COOH groups of the CMGs, giving rise to the final composite materials, namely polystyrene-b-poly(isoprene)-g-CMGs, which exhibited enhanced physicochemical properties. The successful synthesis was determined through multiple molecular characterization techniques together with thermogravimetric analysis for the verification of increased thermal stability, and the structure/properties relationship was justified through transmission electron microscopy. Furthermore, the arrangement of CMGs utilizing lamellar and cylindrical morphologies was studied in order to determine the effect of the loaded CMGs in the adopted topologie

p-Doping of a Hole Transport Material via a Poly(ionic liquid) for over 20% Efficiency and Hysteresis-Free Perovskite Solar Cells

An efficient metal-free formulation of a hole transport material (HTM) based on an ionic liquid polymer is developed for n-i-p perovskite solar cells (PSCs), to address reproducibility issues related to the use of complex dopant mixtures based on lithium salts and cobalt coordination complexes. The conductivity of the HTM is thus significantly improved by 4 orders of magnitude, up to 1.9 x 10-3 S.cm-1, using poly(1-butyl-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide) (PVBI-TFSI) as dopant. Introduced in the FTO/c-TiO2/mp-TiO2/K0.05(MA0.15FA0.85)0.95PbI2.55Br0.45/HTM/Au PSC configuration, PVBI-TFSI-HTM formulation shows power conver-sion efficiency as high as 20.3 %, versus 18.4 % for the standard lithium salt-HTM formulation, with considerably re-duced hysteresis and excellent reproducibility. Mechanistic investigations suggest that PVBI-TFSI acts as a source of protons promoting the HTM oxidation

Metal Residues in Semiconducting Polymers: Impact on the Performance of Organic Electronic Devices

The effect of impurities on the optoelectronic and charge transport properties of semiconducting polymers was investigated through the performance of organic photovoltaics (OPVs) and organic field effect transistors (OFETs), respectively. A model representative semiconducting polymer, i.e., poly­(3-hexylthiophene) (P3HT), was synthesized and purified using different methods such as precipitation, metals’ complexation, and Soxhlet extraction. After the purification processes, each fraction was analyzed to determine its composition in metals (impurities) by various techniques. OFETs and OPVs fabricated from these purified polymer fractions were found to show different charge carrier properties and photovoltaic behaviors. The purest fraction which was obtained after Soxhlet extraction complemented by metals’ complexation with the help of ethylenediamine and 15-crown-5 ether showed the best performance in both OPVs and OFETs

Hierarchical self-assembly of nanoparticles for optical metamaterials

Hierarchical self-assembly arranges nanostructures at different length scales. It gradually becomes an effective method of fabricating artificial metamaterials from composite nanostructures tailored for a particular response. Hierarchical self-assembly overcomes shortcomings of "top-down" methods by significantly reducing fabrication time and making it possible to form bulk materials. Here we report an application of hierarchical self-assembly of metal nanoparticles for the creation of the first isotropic optical metamaterial with strong artificial magnetism in blue light. We have used colloidal self-assembly to create artificial "nanomolecules" that generate the desired magnetic response and microfluidic self-assembly to produce a bulk metastructure. We demonstrate that the magnetic response of the final material is accurately described by an isotropic magnetic permeability that satisfies the principle of locality. Our approach unlocks the fabrication of large volumes of composite nanomaterials. Moreover, the spatial disorder inherent to this "bottom-up" method holds the key to solving the non-locality problem. The technique can be readily extended to the future generations of low-loss optical metamaterials made of dielectric nano-blocks to bypass the limitations of optical losses associated with plasmonic resonances in noble metals.Initiative d'excellence de l'Université de Bordeau