POLYMERS BELOW THE THETA-POINT - RENORMALIZATION-GROUP CONSIDERATIONS

The average size of long chains below the theta point is discussed in terms of a continuum model in which the chain is viewed as a collapsed phase perturbed by repulsive pair interactions. The representation of the collapsed phase makes use of the path integral formulation of a c olored noise process introduced in an earlier paper [J. Chem. Phys. 99 , 9230 (1993)], while the pair interactions are approximated as delta function pseudopotentials of strength upsilon(0). By treating the excl uded volume perturbatively, the model can be described (at first order in upsilon(0)) by renormalization group (RG) methods using dimensiona l regularization, epsilon expansion and minimal subtraction of poles. The nature of the fixed points of the RG transformation suggests that the collapse transition may be first order. (C) 1995 American Institut e of Physics.