CROSS-POLARIZATION MAGIC-ANGLE-SPINNING C-13 NUCLEAR-MAGNETIC-RESONANCE STUDY OF THE HOMOGENEITY OF SOME PHOTOPOLYMERIZED ACRYLIC NETWORKS

A theoretical analysis of relaxation processes has been used in the qu alitative interpretation of carbon-resolved, proton T-1 rho data obtai ned at 100.56 MHz for three solid polyacrylate networks made by photop olymerization of the polyol acrylate monomers poly(ethylene glycol) di acrylate (PEGA), trimethylolpropane triacrylate (TMPTA), and dipentaer ythritol pentaacrylate (DPHPA). This analysis permits an estimate of t he spin diffusion rates between different chemical species. Such rates are strongly dependent on spatial proximity and hence are applicable to the determination of the homogeneity of the networks. Proton T-1 rh o's in networks are not quite averaged to a single value by spin diffu sion like in polymer blends, indicating there is extensive intermixing of TMPTA and DPHPA in forming the network. Proton T-1 rho, experiment s are sufficiently sensitive to distinguish between a TMPTA/DPHPA netw ork and PEGA homopolymer. When glass fibers are present in the network , they act like a spin diffusion medium, producing an increase in the rates of relaxation for all three components of the network.