Equation-of-state exchange parameters of poly(methyl methacrylate) with some aliphatic esters

The retention diagram of poly(methyl methacrylate) with n-nonane and ethyl acetate was obtained at temperatures between 80°C and 200°C by gas chromatography. Thermodynamical equilibration was reached beyond 160°C. The parameters of hard-core polymer–solvent interaction, χt∞, effective exchange energy, X12 , exchange enthalpy, X12 and exchange entropy, Q12 were determined for the polymer with solvents such as methyl acetate, ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, tert-butyl acetate and isoamyl acetate at temperatures between 175°C and 195°C. It was observed that the value of parameter χt∞ decrease, i.e. the solubility of polymer increase as carbon number and branching of the alkyl group in the solvent increase at studied temperatures. The polymer exhibits exothermic solubility in lower molecular weight esters such as methyl acetate and ethyl acetate but it exhibits endothermic solubility as the molecular weight of the ester increase.