Dynamics of propylene carbonate confined in poly(methyl methacrylate) gels

Broad band dielectric spectroscopy has been performed on a polymer gel consisting of propylene carbonate (PC) stabilised with a polymer matrix, poly(methyl methacrylate) (PMMA). The gel is macroscopically (>10 μm) homogenous as revealed by spatially resolved Raman spectroscopy. The dielectric response for the polymer gel is compared to that of pure PC under identical experimental conditions and a dielectric loss peak can be observed at similar temperatures in both systems. For pure PC this is the well-known α-relaxation peak and for the polymer gel we therefore attribute the loss peak to the confined PC relaxation. The loss peak for the polymer gel is considerably broader and shifts to lower frequencies. Crystallisation of PC is avoided by fast cooling through the melting point to below the glass transition temperature. The confinement effectively inhibits crystallisation of the PC in the polymer gel and the modified α-relaxation can be observed over a large temperature and frequency range, in contrast to pure PC which crystallise at roughly 182 K.