WATER IN METHACRYLATES .2. DYNAMIC MECHANICAL-PROPERTIES OF SWOLLEN POLY POLY(2-HYDROXYETHYL METHACRYLATE-CO-GLYCOL DIMETHACRYLATE) NETWORKS

The effects of copolymer composition and water content on shear modulus were determined by torsion-pendulum measurements. Water had a plasticizing effect on all samples tested, but the effect of water content and copolymer composition did not conform to extant empirical and theoretical relationships. The glass transitions broadened with increasing water content at low values and became sharper again at higher water contents. The results are interpreted in terms of the microheterogeneity of the networks being manifest in the range of dynamic environments experienced by segments of the networks. Subambient transitions were observed. The results suggest that the gamma-transition of the dry networks is replaced by the diluent transition, T(dil), in the wet networks. The beta-transition was in most cases obscured by the broadening of the glass-transitions.