CHIROPTICAL PROPERTIES OF A CHIRAL-SUBSTITUTED POLY(THIENYLENE VINYLENE)

Poly(3,4-bis[(S)-2-methylbutoxyl-2,5-thienylene vinylene) (BMB-PTV), t he first example of a PTV derivative with optically active side chains , was prepared using a TiCl4/Zn-induced coupling of the monomeric dial dehyde. The linear absorption spectra of BMB-PTV exhibit a strong solv atochromic effect: lambda(max) = 601 nm in a good solvent and lambda(m ax) = 570 nm in a poor solvent. In good solvents the polymer chains co ntain a high degree of intrachain order, while optical activity associ ated with the pi-pi transition is absent. In contrast, the solvatochr omic shift observed in poor solvents is accompanied by the emergence o f a strong activity in circular dichroism spectroscopy, attributed to the formation of chiral superstructures of multiple chains. Chiral sup erstructures or microaggregates are also present in the solid state (s pin-coated films) and their concentration can be altered by annealing.