Alkyl side-chain length effects on fluorescence dynamics, lamellar layer structures, and optical anisotropy of poly(diphenylacetylene) derivatives

A study was conducted to evaluate the fluorescence efficiency and optical anisotropy of poly(diphenylacetylene) derivatives having n-octyldimethylsilane and trimethylsilane moieties, in the side chain. The effects of alkyl length on fluorescence quantum efficiency, main-chain stiffness, and optical order parameter of poly(diphenylacetylene) were evaluated. The study found that the longer alkyl groups in the side chains correlated with longer lifetimes. An increase in the alkyl length increased intrinsic viscosity and main-chain stiffness. A longer alkyl group was found more effective at aligning the polymer chain parallel to the shearing direction than a shorter alkyl group. Molecular design of emissive conjugated polymers with high quantum yield and large optical anisotropy was prepared in the study.