Structural Relaxation and Refractive Index of Low-Loss Poly(methyl methacrylate) Glass

摘要

Amorphous polymer glasses are essentially in ther-modynamic non-equilibrium states. Physical aging~1 describes the timne dependence of change in the behavior of a polymer glass held at tmeperatures below the glass transition. Such change is normally the result of continuous slow relaxation of the glass from its initial non-equilibrium state towards the final thermodynamic equilibrium state. Thermodynamical properties such as volume~2,3 or enthalpy~4,5 have been mainly considered for the study of this p0henomenon. Many properties of amorphous polymer glasses are affected by aging. Recently, we investigated the effects of enthalpy relaxation on light scattering loss of low-loss Poly(methyl-methacrylate) (PMMA) glass which had no excess scattering, and concluded that light scattering loss of glassy PMMA is not affected inherently by physical aging due to approach to thermodynamic equilibrium at a temperature below glass transition temperature (T_g).~6