Study of conformational-segmental mobility in linear polyethylene and isotactic polypropylene by the spin probe method

Abstract

A general version of the Kusumoto-Bullock free-volume model for reorientation dynamics of spin probe in solid polymers is described. Its application enables one to obtain simultaneously the size parameter of a segment and the kinetic-energy parameter of segmental mobility. These data, along with theoretical knowledge of the conformational microstructure and conformational dynamics, allow a discussion of molecular mobility in terms of concrete conformation-segmental motion mechanisms. Participation of one-barrier transitions of the typePptqQ→Pp′g ± q′Q, and two-barrier transition of the type gauche-migration, creation and annihilation of kink sequence was observed for linear polyethylene. In agreement with the conformational microstructure, it was found for isotactic polypropylene that Schatzki's crankshaft motions of four-member segments might be involved.