Photopolymerization of Polyfunctional Acrylates and Methacrylate Mixtures:  Characterization of Polymeric Networks by a Combination of Fluorescence Spectroscopy and Solid State Nuclear Magnetic Resonance

Abstract

Fluorescence spectroscopy and solid state NMR methods were used to elucidate the detailed molecular structure of poly(meth)acrylate networks. Both techniques can be employed on identical samples and give complementary information. In this study a series of diacrylates, a series of dimethacrylates, and 1:1 mixtures of the triacrylate TMPTA with diacrylates (DA's) or dimethacrylates (DMA's), respectively, was investigated. Fluorescence spectroscopy was performed, using the shift in the fluorescence maximum of 4-(dimethylamino)-4‘-nitrostilbene ( 1 ), a charge transfer probe. This probe monitors both the rigidity and the polarity of the medium in which it is incorporated. CPMAS 13 C NMR spectroscopy was employed monitoring the relaxation times, T 1, of carbon atoms from the main chains and pendant groups, determining cross-link densities, and measuring T 1 ρ ( 1 H) values. With these techniques information about the mobility of individual atoms and the homogeneity of the polymeric networks is obtained.