2ND VIRIAL-COEFFICIENT OF A(X)B(Y) MIKTOARM STAR COPOLYMERS IN COMMON-THETA, COMMON GOOD, AND SELECTIVE SOLVENTS

The mutual second virial coefficient A(2) between two identical ideal miktoarm star copolymer chains A(x)B(y) composed of A and B branches i s determined up to the first order of the small parameter epsilon = 4 - d (d is the space dimensionality) by means of simple perturbation th eory. Analytical expressions corresponding to various macroscopic stat es, as those are defined by the prevailing binary intermolecular inter actions, are obtained as a function of the arm lengths N-A, N-B, their corresponding numbers x, y, and the interaction parameters, between u nits of similar or dissimilar kind u(AA), u(BB), and u(AB). The effect of the copolymer architecture is also studied in detail by calculatin g g(A), the ratio of the virial coefficient of a miktoarm star with re spect to that of a linear diblock copolymer with the same number of A and B units; g(A) is dimensionless and experimentally accessible.