Estimation of the Interaction Parameter between Polystyrene and Poly(p-chlorostyrene) from Osmotic Pressure Measurements

Abstract

The composition dependences of the osmotic second virial coefficients A2 for the mixtures of polystyrene (PSt) and poly(p-chlorostyrene) (PClSt) and for the block copolymers of ABA and BAB types (A, PSt; B, PClSt) were studied in toluene, 2-butanone (MEK), and cumene solutions. All the samples were prepared by anionic polymerization and they are close in molecular weight which is ca. 35×104. It was found that in toluene and MEK, plots of A2 vs. composition obtained for the polymer mixtures and for the block copolymers of ABA and BAB types fell on a single curve in the respective solvents, whereas in the selective solvent, cumene, A2 value of the polymer mixtures was smaller than that of the block copolymers with the same composition. The thermodynamic interaction parameter χAB between PSt and PClSt was estimated from A2 data, according to the theories of dilute polymer solutions; the χAB values obtained from A2 for the ternary system of PSt–PClSt–solvent were 0.086 (in toluene) and 0.063 (in MEK), and those from A2 for the block copolymer solutions were 0.076 (in toluene), 0.064 (in MEK) and 0.063 (in cumene). χAB=0.070±0.016 was obtained as the average.