Poly(3,3' '-dioctyl-2,2':5',2' '-terthiophene), a polymer recently used for the fabrication of organic field effect transistors, has been fractionated into five fractions distinctly differing in their molecular weights (Mn), with the goal of determining the influence of the degree of polymerization (DPn) on its principal physicochemical parameters. It has been demonstrated that within the Mn range studied (from 1.5 kDa to 10.5 kDa by SEC), corresponding to DPn from 10 to 38, the polymer band gap steadily decreases with growing molecular weight, which is clearly manifested by an increasing bathochromic shift of the band originating from the pi-pi* transition. The same trend is observed for the HOMO level, determined from the onset of the p-doping in cyclic voltammetry, which shifts from -5.10 eV to -4.90 eV for the lowest and the highest molecular weight fractions, respectively. The most pronounced influence of DPn has been found for the charge carriers' mobility-one of the most important parameters of field effect transistors (FETs) fabricated from this polymer. A fourfold increase in DPn results in an increase of the carriers' mobility by more than 3 orders of magnitude. Comparison of these results with those obtained for fractionated regioregular poly(3-hexylthiophene) shows a strikingly similar behavior of both polymers with respect to the molecular weight.

We describe the preparation of solution-processible hybrid polymers, consisting of a polythiophene main chain and randomly distributed alkyl and oligoaniline side groups. The proposed procedure involves three steps:  copolymerization of alkyl- and ester-group-substituted thiophenes to give the precursor polymer, followed by the hydrolysis of the pendant ester groups and aniline tetramer grafting through an amidation reaction. The proposed method is more versatile than previously used copolymerization procedures because higher tetraaniline grafting levels can be obtained. The postfunctionalized polymer is electrochemically active both in its oligoaniline part and in its conjugated polythiophene main chain. As shown by complementary voltammeric and UV−vis−NIR and Raman spectroelectrochemical studies, the polymer can be electrochemically doped selectively in its side oligoaniline chains or globally in the main chain as well as in the side chains. Selective side-chain doping can also be achieved chemically through protonation of the grafted oligoaniline groups in their semi-oxidized state. Doping with FeCl3 is global and involves the oxidation of the main chain and Lewis acid complexation of the side chains, as shown by Mössbauer spectroscopy.

New processable, electroactive, alternate copolymers consisting of dialkylbithiophene units and oligoanilinethiophene units have been prepared by post-polymerization functionalization of a specially prepared precursor polymer, namely poly [(4,40-dioctyl-2,29:59,20-terthiophene-39-yl)ethyl acetate], carried out via its hydrolysis and consecutive branching aniline dimer or tetramer through the amidation reaction. The precursor polymer is interesting by itself because it gives a very clear spectroelectrochemical response over a very narrow potential range. The proposed method enables the preparation of regiochemically better defined alkylthiopheneoligoanilinethiophene copolymers with higher content of oligoaniline side groups as compared to previously used methods. Cyclic voltammetry investigations combined with UV-vis-NIR, EPR and Raman spectroelectrochemistry show that both the oligoaniline side groups and poly(thienylene) main chain are electrochemically active. Significant differences for the side group electrochemistry are observed in acidified and nonacidified electrolytes making the prepared new copolymer a good candidate for electrochromic applications in diversified electrolytes.

Using postpolymerization functionalization, we have prepared a new solution-processable electroactive polymer combining electrochemical properties of poly(thiophene)s and oligoanilines. The elaborated procedure consists of three steps. First, 3-octylthiophene and ethyl 3-thiopheneacetate are copolymerized to give poly(3-octyl-2,5-thienylene-co-3-methylene-ethylcarboxylate-2,5-thienylene)the precursor polymer. The precursor is then hydrolyzed, and in the last step, aniline dimer is attached to it via amidation reaction. UV−vis−NIR and Raman spectroelectrochemical studies combined with cyclic voltammetry show that, as expected, both poly(thienylene) main-chain and dianiline side groups can be oxidatively doped, the latter adopting, upon oxidation, the structure of semiquinone radical cation.

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