Selective Anionic Polymerization of 2,5-Divinylthiophene Derivatives

Selective anionic polymerization of 2,5-divinylthiophene was conducted at one of its two vinyl groups in a living manner using oligo­(α-methylstyryllithium) (αMSLi) and a 10-fold excess of tBuOK as a binary initiator system in tetrahydrofuran at −78 °C. 2-Isopropenyl-5-vinylthiophene (iPrVT), an asymmetric divinyl monomer, also underwent selective anionic polymerization under the initiation of αMSLi/tBuOK to yield a polymer with a predictable molecular weight (Mn < 9.0 kg/mol)) and a narrow molecular weight distribution (Mw/Mn < 1.15). In each case, the binary initiator system of αMSLi/tBuOK effectively prevented the side reactions of the propagating anion with the residual vinyl or isopropenyl groups. A weak 1H NMR signal (∼5%) of the residual vinyl groups was observed for the resulting poly­(iPrVT) along with dominant signals of the isopropenyl group, suggesting that the isopropenyl group of iPrVT also participated in the polymerization but to a significantly lesser extent. The obtained polymers exhibited glass-transition temperatures (∼75 °C) as well as typical exothermic peaks (>120 °C) owing to thermal cross-linking, confirming the reactivity of the residual vinyl groups in the repeating unit of the polymer