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 t ested by dynamic mechanical thermal analysis (DMTA) at 1 Hz. Three ure thane acrylates of different chain length were copolymerized with meth yl acrylate and two diacrylates and storage moduli and glass transitio n temperature measured. The symmetric width or multiplicity of the gla ss transition peaks were taken as indications of the degree of heterog eneity of the network. The diacrylate monomers formed two phases with distinct glass-transitions; with the two highest molar-mass urethane a crylates-methyl acrylate only with the highest. CPPEMAS C-13-NMR time constants T1rho(C) and T(SL) were measured for copolymers of one ureth ane acrylate to sample network motion at the molecular level in 60 kHz and near static domains.