Thermodynamics of Dissolution of TOPAS Polycycloolefins in Chloroform

Abstract

The thermodynamic functions (Gibbs free energy, enthalpy, and entropy of mixing) of TOPAS polycycloolefins (ethylene–norbornene copolymers) in chloroform at 298 K have been determined using microcalorimetry and isothermal equilibrium sorption of solvent vapor. TOPAS-5013 and TOPAS-8007 copolymers with norbornene contents of 46 and 35 mol%, respectively, have been studied. The concentration dependences of the thermodynamic dissolution functions have been examined for samples obtained by various methods: pressed commercial pellets and copolymer films cast from chloroform solutions. Thermodynamic modeling was used to calculate the Flory–Huggins enthalpy parameter and parameters characterizing the nonequilibrium state of the polymer glass. It has been shown that intermolecular interaction with chloroform is characterized by a Flory–Huggins enthalpy parameter of 0.25 ± 0.04 and is almost independent of the copolymer composition and the film fabrication method. At the same time, the proportion of metastable vacancies as a parameter of the glassy structure depends on both factors. The degree of nonequilibrium of the glassy state of TOPAS copolymers decreases with decreasing norbornene content in the copolymer chain and in the case of solvent-based film casting.