Chiroptical properties of a chiral-substituted poly(thienylene vinylene)

Poly(3,4-bis[(S)-2-methylbutoxy]-2,5-thienylene vinylene) (BMB-PTV), the first example of a PTV derivative with optically active side chains, was prepared using a TiCl4/Zn-induced coupling of the monomeric dialdehyde. The linear absorption spectra of BMB-PTV exhibit a strong solvatochromic effect: λmax=601 nm in a good solvent and λmax=570 nm in a poor solvent. In good solvents the polymer chains contain a high degree of intrachain order, while optical activity associated with the π-π* transition is absent. In contrast, the solvatochromic shift observed in poor solvents is accompanied by the emergence of a strong activity in circular dichroism spectroscopy, attributed to the formation of chiral superstructures of multiple chains. Chiral superstructures or microaggregates are also present in the solid state (spin-coated films) and their concentration can be altered by annealing.