Solid polymers, dielectric relaxation

Williams, G. Molecular Aspects of Multiple Dielectric Relaxation Processes in Solid Polymers. Vol. 33, pp. 59—92. 

Wilkes, G. L. The Measurement of Molecular Orientation in Polymeric Solids. Vol. 8, pp. 91-136. Williams, G. Molecular Aspects of Multiple Dielectric Relaxation Processes in Solid Polymers. Vol. 33, pp. 59-92. 

The approach developed in this paper, combining on the one side experimental techniques (dynamic mechanical analysis, dielectric relaxation, solid-state 1H, 2H and 13C NMR on nuclei at natural abundance or through specific labelling), and on the other side atomistic modelling, allows one to reach quite a detailed description of the motions involved in the solid-state transitions of amorphous polymers. Bisphenol A polycarbonate, poly(methyl methacrylate) and its maleimide and glutarimide copolymers give perfect illustrations of the level of detail that can be achieved. 

In another paper in this issue [1], the molecular motions involved in secondary transitions of many amorphous polymers of quite different chemical structures have been analysed in detail by using a large set of experimental techniques (dynamic mechanical measurements, dielectric relaxation, H, 2H and 13C solid state NMR), as well as atomistic modelling. 

Reorientation dynamics of molecular tracers in polymers is not only important for the understanding of slow relaxation phenomena in glassy polymers but plays also a critical role in practical problems such as molecular design of nonlinear optical materials with long-term stability based on dyes/polymers complexes. We show here the reorientation dynamics of molecular tracers in glassy polymers obtained by the armealing-after-irradiation method described below. These experimental results are compared to the local relaxation processes of glassy polymers obtained by the already established measurement techniques such as dielectric relaxation and solid state NMR. Finally, the molecular interpretation of the relaxation of free-volume distribution in polymers will be discussed. 

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