Thermodynamics of polymer solutions. Part 2.—Polyisobutylene and benzene
Solvent activities in polyisobutylene-benzene solutions have been determined over the range of segment fraction φ2 from 0.31 to 0.96 at the temperatures 10,25 and 40°C. The 25°C isotherm is in agreement with the previous results of Flory and Daoust and of Jessup. The partial molar enthalpies of the solvent are large and strongly dependent on concentration, in accord with the measurements of Bawn and Patel. Partial molar entropies of dilution are smaller than the lattice combinatory result. The excess volume of mixing at 24.5°C and at φ2= 0.5 is ca. 0.35 %. The theory described in part 1 succeeds in accounting for the principal features of the PIB-benzene system. It correctly predicts a positive excess volume but overestimates its magnitude; the residual chemical potential and partial molar entropy are fairly well reproduced.