Evaluation of local polarity of polymer solids by a rigid fluorescent probe of carbazole-terephthalate cyclophane

A novel rigid fluorescent probe, carbazole - terephthalate cyclophane (Cz-TP) was applied to evaluate local dielectric constants (E) of various polymer solids in a wide range of temperatures. For poly(vinylidene fluoride), the e increased above the glass transition temperature (T-g), due to relaxations of the polar segment -(CH2CF2)- of the main chain. For poly(alkyl methacrylate)s, the epsilon increased above the T-g or the melting temperature of the side chain, where motions of the polar ester groups are activated. For cyanoethylated polymers, the epsilon increased owing to motions of the polar cyano groups at the end of the side chain and the e corresponded to the dielectric constant evaluated by dielectric relaxation measurement at a high frequency, because the Cz-TP exciplex has a lifetime of tens of nanoseconds. For a cyanoethylated polymer with a high content of cyano groups, the e was larger at low temperatures than the dielectric constant obtained by the macroscopic dielectric relaxation measurement. These results show that the Cz-TP molecule is a useful probe for evaluation of the local polarity in polymer solids over a wide temperature range and can detect even a small change in - at transition temperatures such as glass transition, side-chain melting, and side-chain relaxation. (C) 2004 Elsevier Ltd. All rights reserved.