Synthesis, characterization and properties of poly(p-phenyleneethynylene) conjugated polymers containing liquid crystal groups

Two novel poly(p-phenyleneethynylene) (PPE) samples with liquid crystal (LC) groups were synthesized, and their liquid crystal properties and photoluminescent properties were investigated. It was found that the LC properties of these polymers were deeply affected by the density of the side-chain LC groups, and the polymer with high content of LC groups exhibited the obvious smectic mesophase as illustrated by differential scanning calorimetry and polarized optical microscopy. The photoluminescence spectra showed that there was a remarkable change for the LC polymer in the solid film state before and after annealing, likely attributed to the morphological change by thermal annealing. Additionally, Först energy transfer in the concentrated solution was also reported. Moreover, atom force microscope (AFM) images were investigated with the temperature changing. As a result, we concluded that spectra can be altered by the conjugated polymer morphologies with different LC states, and this provided us a promising aspect for the future preparation of controlled light emitting polymers.