SPIN-LABELED GELS OF POLY(METHYL ACRYLATE)

Spin-labelled poly(methylacrylate) (PMA) was investigated by ESR both in the swollen and in the dried gel state. The polymerization was induced by gamma-irradiation; the spin-labelling was carried out by thermal treatment in the presence of 2,4,6-trichloronitrosobenzene. The labelling takes place both on the methine and the methylene carbons of the PMA chain resulting in a triplet and a six-line ESR spectrum respectively. For both radicals, the correlation time is of the order of 10(-9) sec in the swollen gel and 10(-8) sec in the dried gel. The temperature dependence of the ESR signal associated with the three-line radical and six-line radical could be analysed in terms of a diffusion model. The activation energies were determined as 23 and 19 kJ/mol, respectively. The radical structures and reactions are discussed.