POSITRON-ANNIHILATION IN ORIENTED POLY(ME THYL METHACRYLATE)

Structural rearrangements in glassy PMMA on polymer deformation and el astic strain recovery in glassy state were studied by positron annihil ation lifetime spectroscopy. Uniaxial compression was shown to be acco mpanied by a decrease in concentration of microregions with high free volume in disordered polymer regions, which were characterized by low packing density. Elastic strain recovery at elevated temperatures but below glass transition point T-c proceeds without any noticeable chang es in fractional content of free volume both in disordered and ordered polymer regions. The advantages of positron annihilation lifetime spe ctroscopy for studying microstructure and structural rearrangements in polymers were discussed.