Selective Anionic Polymerization of 2,5-Divinylthiophene Derivatives

Selective anionic polymerization of 2,5-divinylth- iophene was conducted at one of its two vinyl groups in a living manner using oligo(alpha-methylstyryllithium) (alpha MSLO and a 10-fold excess of tBuOK as a binary initiator system in tetrahydrofuran at -78 degrees C. 2-Isopropenyl-S-vinylthiophene (iPrVT), an asymmetric divinyl monomer, also underwent selective anionic polymerization under the initiation of alpha MSLi/tBuOK to yield a polymer with a predictable molecular weight (M-n < 9.0 kg/mol)) and a narrow molecular weight distribution (M-w/M-n < 1.15). In each case, the binary initiator system of alpha MSLi/tBuOK effectively prevented the side reactions of the propagating anion with the residual vinyl or isopropenyl groups. A weak H-1 NMR signal (similar to 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 (similar to 75 degrees C) as well as typical exothermic peaks (>120 degrees C) owing to thermal cross-linking, confirming the reactivity of the residual vinyl groups in the repeating unit of the polymer.

Automated summary

The selective anionic polymerization of 2,5-divinylthiophene and 2-isopropenyl-S-vinylthiophene was successfully conducted under low temperature conditions using oligo(alpha-methylstyryllithium) and excess tBuOK as initiators, resulting in polymers with predictable molecular weight and narrow molecular weight distribution. The binary initiator system effectively prevented side reactions, showing potential for controlled polymer synthesis.