Synthesis of Novel π-Conjugated Rod-Rod-Rod Triblock Copolymers Containing Poly(3-hexylthiophene) and Polyacetylene Segments by Combination of Quasi-Living GRIM and Living Anionic Polymerization

The first successful synthesis of a new rod-rod-rod triblock copolymer, polyacetylene(PA)-b-poly(3-hexylthiophene)(P3HT)-b-PA could be synthesized by a combination of quasi-living Grignard metathesis (GRIM) and living anionic polymerization. We first confirmed that poly(4-tolyl vinyl sulfoxide) (PTVS), which is a soluble precursor for PA, could be synthesized by living anionic polymerization in THF at −78 °C, initiated with 3-methyl-1,1-diphenylpentyllithium as the initiator in the presence of in situ-generated lithium enolate. The molecular weights (MWs) and polydispersities (PDIs) were well controlled (MW = 5,200–27,000, PDI = 1.10–1.22), respectively. A coil-rod-coil triblock copolymer, PTVS-b-P3HT-b-PTVS, (6,000-12,500-6,000) could also be synthesized, initiated with a P3HT-based difunctional macroinitiator in the presence of lithium enolate. GPC-RALLS and 1H NMR analyses confirmed a high degree of structural homogeneity of PTVS-b-P3HT-b-PTVS. A thermal transformation reaction of the polymer was carried out in the film state at 170 °C for 2 h to afford PA-b-P3HT-b-PA quantitatively, as monitored by TGA and FT-IR analyses. The optical and electronic properties as well as the morphological behavior of the block copolymers were investigated by UV-vis spectroscopy, conductivity measurement, and AFM observation.