A DOUBLE-MODULATION ESR STUDY OF INTERNAL DYNAMICS IN THE GLASSY POLYMER MATRIX DETECTED BY A NITROXIDE SPIN-PROBE

The double-modulation ESR spin-probe technique was employed to study s low-motional dynamics in amorphous polymer matrices of polybutadiene, polyisobutylene, poly(methyl methacrylate), and paraffin. It was shown that the low-lying excitation levels of the polymer matrix, found in the range from 77 to 190 K below the internal spin-probe transition, a ffect the effective relaxation rate of a perdeuterated nitroxide probe . The interrelationship between the effective relaxation rates and the local molecular dynamics of side-chain groups attached to the polymer backbone was observed. Possible relaxation mechanisms are discussed w ithin the electron-nuclear dipolar interaction. (C) 1997 Academic Pres s.