Regioregular Poly(3-alkoxythiophene)s:  Toward Soluble, Chiral Conjugated Polymers with a Stable Oxidized State

Abstract

Chiral poly(3-(3,7-dimethyloctyloxy)thiophene)s were prepared using three different methodologies, rendering polymers with different degrees of regioregularity. In a first attempt, 3alkoxythiophene was polymerized using FeCl 3 , resulting in a highly regioirregular poly(3alkoxythiophene).Secondly, the GRIM methodology was applied, which yielded poly(3alkoxythiophene)s with relatively high, but not perfect, degrees of regioregularity. Finally, an alternative methodology was used, which consisted of the exclusive formation and subsequent 2 polymerization of 2-bromomagnesio-3-(3,7-dimethyloctyloxy)-5-bromothiophene) and which resulted in poly(3-alkoxythiophene)s with (almost) perfect regioregularity. The degrees of regioregularity were evaluated with 1 H NMR, UV-Vis and CD spectroscopy and cyclic voltammetry. These (regioregular) poly(3-alkoxythiophene)s show a very high λ max , indicating very high conjugation lengths. Moreover, the polymers could easily be oxidized and they were stable in both neutral as well as oxidized state.This stability can be correlated with the decrease in oxidation potential. The reproducibility and reversibility of the oxidation was demonstrated by UV-Vis spectroscopy. Finally, the chiral properties of the polymers were investigated with circular dichroism spectroscopy. These experiments demonstrated again the difference in regioregularity of the polymers.

β‐Substituted Terthiophene [2]Rotaxanes

“…[14] After the alkylation of the hydroxyl group (3), debromination at 2-position was carried out by the lithiation with nBuLi in ether, followed by the treatment with water. [15] Although the 3,5-substituted product (4) was able to be separated from the 2,3-substituted product through silica gel chromatography, it was difficult to obtain pure product, owing to the small difference in R f values. Deprotection of the hydroxyl group afforded the b-substituted thiophenebromide (5).…”

Ni‐Catalyzed Polymerization of Poly(3‐alkoxythiophene)s

“…[6] ; (bisdiphenylphosphino)-2-methyl-4-trimethylsilylacetylenenickel bromide was prepared analogously as described in reference 9.…”

“…[6][7][8] To verify the chain-growth nature of the polymerization of P3AOT, the correlation between the molar mass of the polymer and the ratio of the initial monomer concentration to the initiator concentration was studied. All polymerizations were carried out at room temperature, varying the amount of Ni-catalyst, but keeping the initial concentration of 1 constant.…”

“…[6] As a consequence, the Grignard metathese method (GRIM), starting from the dibromothiophene derivative -as is used for the chain-growth polymerization of HT-P3AT -cannot be employed for the polymerization of HT-P3AOT, since this methods produces both isomers. [10] Also a selective GRIM on 2-iodo-5-bromo-3-alkoxythiophene, even if iPrMgCl·LiCl was employed, was unsuccessful in our hands.…”

“…Regioregular HT-coupled poly(3-alkoxythiophene)s (P3AOTs) are electronically different and show a significantly higher  max compared to P3ATs. [6] Their Faraday rotation is much larger (Verdet constant up to 3x10 6 T -1 m -1 ) [7] and their magnetic properties differ [8] . Although their properties are interesting, the polymerization behavior of P3AOTs has never been studied in detail.…”