Effect of external influences on the structural and dynamic parameters of medicinal copolymers

Abstract

ESR spectroscopy, DSC, IR spectroscopy are used to study the molecular dynamics, mechanical properties, the ability to ozone oxidation of ethylene-propylene copolymer (SEPE) and a copolymer of ether and urethane groups (SPEU). The behavior of the copolymers under tensile stress changes dramatically upon addition of > 5% ethylene units to polypropylene. Reversible deformation of oriented copolymers containing <5% ethylene units is accompanied by an increase in molecular mobility, with the opposite tendency being observed at a higher content of ethylene units. The sorption properties change in parallel with the molecular mobility. Samples containing >5% ethylene units turn out to be less resistant to ozone oxidation. Upon deformation of isotropic and weakly oriented SPEU sample, molecular mobility increases at the initial stage of stretching, decreasing throughout the strain range covered. Ozone oxidation, both in the loaded and unloaded states leads to an increase in the rigidity of SPEU chains, which manifests itself in the growth of the modulus of elasticity, correlation time, and activation energy. Thermal annealing in water also increases the rigidity of SPEU molecules.