400- and 750-MHz one- and two-dimensional nuclear magnetic resonance spectra of x-ray-degraded poly(methyl methacrylate): comparison with UV-degraded material

摘要

Abstract: Nuclear magnetic resonance spectroscopy (NMR) has been sued for he identification of several products from syndiotactic- rich poly(methyl methacrylate) (PMMA) sheet exposed to x-ray and UV irradiation. Two chain-scission products and two chain-intact products were observed using 1D and 2D NMR spectroscopy. The 750 and 400 MHz 1D hydrogen ($+1$/H) spectrum and the 2D $+1$/H, $+1$/H-COSY, $+1$/HMQC$+1$/ and HMBC$+1$/ spectra permitted the assignment of many hydrogen and carbon NMR signals for the four products which are still polymeric. Additional signals were observed for minor stereoisomers. Methyl formate, s small molecular product, was found in both the x-ray and UV degradations. Acetaldehyde was also observed from x-ray exposure but not UV exposure. Important results from this work are well- resolved chemical 'fingerprints' for x-ray and UV exposed PMMA. !4