Vapour-liquid equilibria and segment-molar excess gibbs free energies of concentrated poly(butyl methacrylate) solutions

Solvent activities were measured by an isopiestic sorption technique for solutions of poly(butyl methacrylate) and poly(tert-butyl methacrylate), respectively, in various solvents between 323 K and 373 K (or 403 K). The experimental data were reduced to segment-molar excess Gibbs free energies and to χ-functions. There is a clear difference in the thermodynamic behaviour of both polymers in their corresponding solutions due to the steric effect of the tert-butyl group. The chain-of-rotators equation-of-state model was used to calculate the thermodynamic quantities applying a group-contribution approach. In general, good agreement can be observed between experimental and calculated results.