Chain dimensions of polystyrenes diluted with low molecular weight homologues

Chain dimensions of polystyrenes diluted with benzene, styrene monomer, and low molecular weight homologues were measured by small-angle neutron scatt ering. Polystyrenes were confirmed to be expanded in monomer and in the hom ologues having sufficiently low molecular weights when polymer concentratio ns are low, and the concentration dependence of the expansion factor gets w eaker with increasing degree of polymerization, N-S, of "diluent". The crit ical N-S value, N-S,N-c, which is the maximum value to give the excluded vo lume effects: is much higher than the theoretical prediction, N-S,N-c appro ximate to N-L(1/2), where N-L is the degree of polymerization of the "solut e" polymer. (C) 1999 Elsevier Science Ltd. All rights reserved.