Nematic polymers: hairpins, ringlets and excimer fluorescence

Abstract

Short liquid crystalline polymers in a nematic environment are very unlikely to cyclise. Hairpins, abrupt chain folds, favour cyclisation. As a result the cyclisation rate constant exhibits a maximum as a function of chain length. The maximum corresponds to a new object, a “ringlet”. The rate constant also depends exponentially on temperature. This suggests excimer fluorescence as a probe of configurations and dynamics of main-chain liquid crystalline polymers.