Second virial coefficients of homopolymers and copolymers of butadiene and styrene in tetrahydrofuran

Second virial coefficients have been measured in tetrahydrofuran for a series of anionically polymerized narrow distribution homopolymers and copolymers of butadiene and styrene. The results fit the general empirical equation A2 = M−1/4(0.0216wB + 0.00995wS + CwBwS), where M is the polymer molecular weight, wB and ws are the weight fractions of butadiene and styrene, and C is a constant which is zero for block polymers and equal to 7.9 × 10—3 for random copolymers. The equation is independent of the degree of 1,2 addition of butadiene and fits data on both linear and tetrachain star‐branched polymers within experimental error.