BEHAVIOR OF A POLYMER-CHAIN IN A CRITICAL BINARY SOLVENT

We present a field-theoretic renormalization group analysis of a polym er chain immersed in a binary good solvent close to its critical demix ing point. We first show that this problem can be mapped on a bicritic al field theory, i.e. a (phi(2))(2)-model with a mass anisotropy. This implies that the end-to-end distance of the polymer is now controlled by a new critical exponent nu(B) related to the quadratic mass anisot ropy operator B. To show this, we solve the RG equation and calculate explicitly the exponents and the mean end-to-end length of the chain.