Molecular motion of the PMMA chain in poly(methylmethacrylate)/poly(vinylidene fluoride) blends by spin trapping labeling

Spin trapping is used to study molecular motion of PMMA chains in blends of poly(methyl methacrylate)/poly(vinylidene fluoride) (PMMA/PVDF). Free radicals produced by thermal degradation of PMMA chains in the blends are trapped by 2,4,6-tri-tert-butylnitrosobenzene, and the spin-labeled chain ends are studied by electron spin resonance (ESR). The temperature dependence of the ESR spectra changes substantially as a function of the PVDF content of the blend. The narrowing curve of the outermost splitting widths and the generation curve of the mobile fraction of the spin label shift to low temperatures with increasing PVDF content of the blend. The decay of the spin label follows second-order kinetics, and the rate constant increases with increasing PVDF content of the blend. The decay reactions are interpreted in terms of a bimolecular reaction of the spin label and translational diffusion of the PMMA chains. These phenomena indicate that the rotational and translational molecular motions of the PMMA chains are closely related to the compatibility of the PMMA and PDVF in the noncrystalline region of the blends. 12 ref.--AA