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The spin-probe method was used to investigate the structure of composites prepared by blending of polyethylene with various contents of silica. When compared to original polyethylene, the temperature T50G was found to be lower at low filler content (4.7, 9.1%), but higher at high filler content (16.6, 25.9%). A relation between T50G and Tg, as derived by A. T. Bullock [1], was used to calculate free volume of the composites in question at temperature Tg (vfg). Average free volume was found to be much higher in samples with low silica content than in original PE, whereas at higher filler content the probe molecules are bound to the filler surface and Bullock's equation can not be applied.

Hyperfine splitting constants of the nitroxyl radical, with and without hydrogen bonds to the surrounding molecules, have been calculated using the UHF method on a 6-31G * base. In polyethylene filled with silica, hydrogen bonds are formed between nitroxyl radicals and -OH groups of the filler. The formation of hydrogen bonds leads to a change in the A ZZ value from 3.33 mT for an isolated nitroxyl radical to 3.83 mT for a radical with a hydrogen bond. The relevant values as measured experimentally are 3.4 and 4.0 mT, respectively. The same procedure was used to calculate the theoretical A ZZ value for a nitroxyl radical interacting with polyamide via a hydrogen bond. The value was found to be 3.63 mT (experimental value= 3.6 mT)

The segmental size in amorphous poly(ethylene terephthalate) (PET) was determined by two methods: a) from deformational behavior of amorphous samples in the elastic state by optical birefringence measurement, and b) from dynamic behavior of a small spin probe by ESR measurement of correlation times. The use of the network model for orientation of segments in amorphous polymer and of the generalized free-volume model for re-orientation of the probe in the amorphous phase gave comparable values ofn=2.3 and 2.1 structural units/segment. We conclude that trans ⇌ gauche conformational transitions of rather small macromolecular segments are the basic motion mechanism in αa-segmental mobility in PET.

Analysis of the structure of nine polymers, in terms of the average size of free volume at T 50G for spin probe Tempo, reveals an empirical connection between this microstructural characteristic of matrices and the change in reorientational regime of the spin probe.

A detailed study has been made of the rotation of the spin probe 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TANOL) in the regime of fast motion in poly(isobutylene) using the activation energy; a free volume model of the probe mobility in the condensed phase is described. Results of the applications of exact and approximate treatments of the generalized free volume model are compared. An analysis of the geometrical and energy parameter of α-mobility has shown that the motion of the probe in the elastic state of the amorphous phase is controlled by local conformational mobility of small segments of the macromolecules.

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.