STRUCTURE AND REACTIVITY OF PMMA ION RADICALS - AN ABINITIO APPROACH

Ab initio molecular orbital (MO) calculations were carried out on the anion radical of methyl isobutyrate, a model of the poly(methylmethacrylate) (PMMA) anion. Calculations were also made on the cation radical for comparison. The results indicates that a strong absorption band at < 320 nm and a weak one at 440 nm were attributed to the pi-pi* and n-pi* transitions of the PMMA anion, respectively. It was found, from the geometry optimization, that the carbonyl group of the anion was bent and the carbonyl oxygen had deviated from the sp2 plane of the carbonyl carbon. Molecular orbital contour maps of singly occupied MO suggested that the excess electrons were mainly distributed on the carbonyl group of the polymer. The stability of the PMMA anion and cation is discussed in terms of the potential energy curves calculated as a function of the O-CH3 distance.