The second virial coefficients of polymethyl methacrylate mixed fractions in acetone

Abstract

Abstract The second virial coefficients of two polymethylmethacrylate fractions of M̄ w = 1.18 × 10 6 and 9.2 × 10 4 and a series of mixed fractions from them have been measured by osmotic pressure and by light scattering in acetone at 25°C. The results show that A is practically insensitive to an admixed lower molecular weight component but very sensitive to any higher molecular weight component contained in the sample. On the contrary, A 2 is sensitive to the lower molecular weight component as well as to the higher molecular weight component present. The values of A 2 and A for the mixed fractions, estimated according to the theory of Flory and Krigbaum, show agreement in the general character of the A 2 ‐ and A ‐composition curves. A broad maximum occurs on the A 2 ‐composition curve around 20% of the higher molecular weight fraction, while a rather sharp maximum occurs on the A ‐composition curve around 6% of the higher molecular weight fraction.