π-Conjugated and conducting polymers represent a class of materials of fundamental interest for organic electronics, optoelectronics, and bioelectronics. Among these, poly(3,4-ethylenedioxythiophene) (PEDOT) serves as a benchmark system due to its high electrical conductivity and chemical stability. However, the insolubility of unsubstituted PEDOT has necessitated the development of synthetic strategies aimed at conferring solution processability and additional functionalities through the introduction of chiral units and side chains on the ethylenedioxy bridge. Two main functionalization strategies exist: monofunctionalization (Mf-EDOT) and C2-symmetric difunctionalization (Df-EDOT); the latter was employed in this work. In this context, this thesis focuses on the design, synthesis, and characterization of a new series of C2-symmetric and chiral EDOT monomers bearing ester side chains of varying lengths (C3 propanoate, C5 pentanoate, and C12 dodecanoate), with the goal of evaluating how the side-chain structure influences molecular packing and polymer backbone conformation. The synthetic sequence involved the preparation of the chiral intermediate (2R,3R)-1,4-dibromobutane-2,3-diol starting from diethyl-L-tartrate. Subsequent transetherification with 3,4-dimethoxythiophene yielded the C2-symmetric precursor (2R,3R)-2,3-bis(bromomethyl)-EDOT (compound 3). Through nucleophilic substitution (SN2) with carboxylic acids followed by electrophilic aromatic bromination (SEAr) with NBS, the diester monomers (4a, 4b, 4c) and their corresponding 2,5-dibrominated derivatives (4a-Br, 4b-Br, 4c-Br) were isolated. Polymerization was carried out via palladium-catalyzed direct arylation polymerization (DArP) [Pd(OAc)2, PivOH, K2CO3 in DMA a 100 °C per 16h] . This methodology was chosen for its high environmental sustainability — avoiding the use of toxic organometallic reagents typical of conventional cross-couplings — and its excellent regioselectivity toward the α/α’ positions of the thiophene ring. The reaction successfully yielded the series of polymers PEDOT C3, C5, and C12. All intermediates, monomers, and polymers were characterized by NMR spectroscopy (1H and 13C), high-resolution mass spectrometry (HRMS), UV-Vis spectroscopy, and gel permeation chromatography (GPC).
I polimeri π-coniugati e conduttori rappresentano una classe di materiali di fondamentale interesse per l'elettronica organica, l'optoelettronica e la bioelettronica. Tra questi, il poli(3,4-etilendiossitiofene) (PEDOT) costituisce un sistema di riferimento per le sue proprietà elettriche e la sua stabilità chimica. Tuttavia, l’insolubilità del PEDOT non funzionalizzato ha reso necessario lo sviluppo di strategie sintetiche volte a conferire processabilità in soluzione e funzionalità aggiuntive attraverso l'introduzione di elementi chirali e catene laterali sul ponte etilendiossidico. sono presenti due strategie di funzionalizzazione: la monofunzionalizzazione (Mf-EDOT) e la difunzionalizzazione e simmetria C2 (Df-EDOT); quest’ultima è stata quella utilizzata in questo lavoro. In questo contesto, il presente lavoro di tesi riguarda la progettazione, la sintesi e la caratterizzazione di una nuova serie di monomeri EDOT C2-simmetrici e chirali recanti catene laterali esteriche a lunghezza ridotta (C3 propanoato, C5 pentanoato e C12 dodecanoato), con l'obiettivo di valutare come la riduzione dell'ingombro sterico influenzi l'impaccamento molecolare e la conformazione delle catene polimeriche. La sequenza sintetica ha previsto l'ottenimento dell'intermedio chirale (2R, 3R)-1,4-dibromobutano-2,3-diolo a partire dal dietil L-tartrato. La successiva transeterificazione con il 3,4-dimetossitiofene ha fornito il precursore C2-simmetrico (2R,3R)-2,3-bis(bromometil)-EDOT (composto 3). Mediante sostituzione nucleofila (SN2) con acidi carbossilici e successiva bromurazione elettrofila (SEAr) con NBS, sono stati isolati i monomeri diesterei (4a, 4b, 4c) e i relativi derivati 2,5-dibromurati (4a-Br, 4b-Br, 4c-Br). La polimerizzazione è stata condotta sfruttando la polimerizzazione per arilazione diretta (DArP) catalizzata da palladio [Pd(OAc)2, PivOH, K2CO3 in DMA a 100 °C per 16h]. Questa metodologia è stata scelta per la sua elevata sostenibilità ambientale evitando l'uso di reagenti organometallici tossici tipici dei tradizionali cross-coupling e per l'eccellente regioselettività verso le posizioni α/α’ del tiofene, che riduce la formazione di difetti di ramificazione (β-defects). La reazione ha consentito di ottenere con successo la serie di polimeri PEDOT C3, C5 e C12. Tutti gli intermedi, monomeri e polimeri sono stati caratterizzati mediante spettroscopia NMR (1H and 13C), spettrometria di massa ad alta risoluzione (HRMS), spettroscopia UV-Vis e GPC.
Sintesi e Polimerizzazione di Derivati EDOT Chirali
RACHETTI, GIULIA
2025/2026
Abstract
π-Conjugated and conducting polymers represent a class of materials of fundamental interest for organic electronics, optoelectronics, and bioelectronics. Among these, poly(3,4-ethylenedioxythiophene) (PEDOT) serves as a benchmark system due to its high electrical conductivity and chemical stability. However, the insolubility of unsubstituted PEDOT has necessitated the development of synthetic strategies aimed at conferring solution processability and additional functionalities through the introduction of chiral units and side chains on the ethylenedioxy bridge. Two main functionalization strategies exist: monofunctionalization (Mf-EDOT) and C2-symmetric difunctionalization (Df-EDOT); the latter was employed in this work. In this context, this thesis focuses on the design, synthesis, and characterization of a new series of C2-symmetric and chiral EDOT monomers bearing ester side chains of varying lengths (C3 propanoate, C5 pentanoate, and C12 dodecanoate), with the goal of evaluating how the side-chain structure influences molecular packing and polymer backbone conformation. The synthetic sequence involved the preparation of the chiral intermediate (2R,3R)-1,4-dibromobutane-2,3-diol starting from diethyl-L-tartrate. Subsequent transetherification with 3,4-dimethoxythiophene yielded the C2-symmetric precursor (2R,3R)-2,3-bis(bromomethyl)-EDOT (compound 3). Through nucleophilic substitution (SN2) with carboxylic acids followed by electrophilic aromatic bromination (SEAr) with NBS, the diester monomers (4a, 4b, 4c) and their corresponding 2,5-dibrominated derivatives (4a-Br, 4b-Br, 4c-Br) were isolated. Polymerization was carried out via palladium-catalyzed direct arylation polymerization (DArP) [Pd(OAc)2, PivOH, K2CO3 in DMA a 100 °C per 16h] . This methodology was chosen for its high environmental sustainability — avoiding the use of toxic organometallic reagents typical of conventional cross-couplings — and its excellent regioselectivity toward the α/α’ positions of the thiophene ring. The reaction successfully yielded the series of polymers PEDOT C3, C5, and C12. All intermediates, monomers, and polymers were characterized by NMR spectroscopy (1H and 13C), high-resolution mass spectrometry (HRMS), UV-Vis spectroscopy, and gel permeation chromatography (GPC).| File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14239/37205