DYNAMIC-MECHANICAL PROPERTIES AND CROSS-POLARIZED, PROTON-ENHANCED, MAGIC-ANGLE-SPINNING C-13-NMR TIME CONSTANTS OF URETHANE ACRYLATES .2. COPOLYMER NETWORKS

Dynamic bulk properties of urethane acrylate copolymer networks were tested by dynamic mechanical thermal analysis (DMTA) at 1 Hz. Three urethane acrylates of different chain length were copolymerized with methyl acrylate and two diacrylates and storage moduli and glass transition temperature measured. The symmetric width or multiplicity of the glass transition peaks were taken as indications of the degree of heterogeneity of the network. The diacrylate monomers formed two phases with distinct glass-transitions; with the two highest molar-mass urethane acrylates-methyl acrylate only with the highest. CPPEMAS C-13-NMR time constants T1rho(C) and T(SL) were measured for copolymers of one urethane acrylate to sample network motion at the molecular level in 60 kHz and near static domains.