Polythiophenes alternating copolymers

This section reviews the synthesis and characterization of random, alternating, block and graft copolymers of thiophenes. A review [2] of processable electronically conducting polymers published in 1991 contains only two references on polythiophene random copolymers and another article [3] describes the synthetic methods used to prepare block and graft copolymers of thiophene. 

Krompiec M, Gmdzka I, Filapek M, Skorka L, Krompiec S, Lapkowski M, Kania M, Danikiewicz W (2011) An electrochromic diquat-quaterthiophene alternating copolymer a polythiophene with a viologen-like moiety in the main chain. Electrochim Acta 56 8108-8114... 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

Chain-growth catalyst-transfer polycondensation (CTP) is a rapidly developing polymerization method, as it allows, in many cases, the above-mentioned limitations of step-growth polymerizations to be overcome. CTP provides a straightforward access to well-defined conjugated homopolymers (e.g., polythiophenes (1), polyfluorenes (2), polyphenylenes (3), etc.), alternate donor-acceptor copolymer e.g., 4) and all-conjugated block polymers (e.g., 5), Chart 20.1. 

This chapter is divided into two main parts polythiophene copolymers and polypyrrole copolymers. Each part reviews the random copolymerization of the heterocyclic monomer and important derivatives, principally those with substituents at the 3-position of thiophene and at the 1- and 3-positions of pyrrole. Alternating, block and graft copolymers are covered in both segments. Because applications of conducting polymers are reviewed in Volume 4, only applications unique to specify copolymers are covered here. In addition, a few theoretical studies dealing with conducting copolymers are reviewed. 

A copolymer of aniline and thiophene was obtained by the Ullmann condensation polymerization of dibromothiophenes and / -phenylenediamines at 185°C [153]. The polymer, consisting of alternative thiophene and aniline units, showed an excellent thermal stability up to 400° C. This alternating structure is confirmed by the infrared spectra, which resemble a superposition of the spectra of polyaniline and polythiophene and molecular-weight determinations. Unfortunately, no conductivity data have been supplied. 

Cyclic voltammetry of the copolymer shows three anodic peaks, two matching the oxidation potentials of the parent homopolymers and a third which is intermediate. Authors attributed the data to the formation of blocks of polypyrrole and polythiophene cormected by blocks of random alternating groups of pyrrole and bithiophene. Increasing the amount of bithiophene in the copolymer produced a strong drop in the final conductivity of the materials, from 17 S cm at 1 mol% to I S cm at 14 mol%. 

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