CHAIN DYNAMICS IN SOLID POLYMERS AND POLYMERIZINGSYSTEMS AS REVEALED BYBROADBAND DIELECTRIC SPECTROSCOPY

摘要

A number of techniques are used to study the chain-dynamics of solid polymers, including those of dielectricrelaxation [1-4], dynamic mechanical thermal analysis (DMTA) [1,5], multinuclear NMR relaxations [6],quasi-elastic dynamic light scattering [7] and neutron scattering [8] (QELS & QENS) and transientfluorescence depolarization (TFD) [9]. Each technique has its own particular probe of the dynamics in amaterial. e.g. dielectric relaxation gives information on the angular motions of molecular chain-dipoles (fordipole relaxation) and the translational motions of ions (for f-dependent electrical conduction); NMRrelaxations relate to the angular motions of chemical bonds; QELS relates to fluctuations in local refractiveindex; QENS to the time-dependent van Hove correlation function (suitably-defined) for proton-containinggroups; TFD to the angular motions of fluorescent groups in a chain. Due to its relevance to practicalapplications of materials, DMTA is pre-eminent among the many physical techniques applied to solidpolymers, but interpretations of behaviour in terms of molecular properties remain difficult since the directlink between an applied macroscopic stress and the molecular response of polymer chains in a bulk materialremains an unsolved problem.