Computer simulation study of a single polymer chain in an attractive solvent

The behavior of a linear polymer chain is studied in a solvent with high affinity for the polymer. The coil dimensions and specific heat are calculated as a function of chain length, solvent concentration, and polymer-solvent attraction strength epsilon(ps). All other interactions are limited to excluded volume repulsion, which implies that the Flory-Huggins chi parameter is negative. Using both on-lattice and off-lattice models of a polymer chain in explicit solvent, we study a transition from weak to strong association regimes. In all cases studied, the system's heat capacity is a nonmonotonic function of epsilon(rhos) with a maximum at attraction strengths of the order of several k(B)T. This peak originates from restriction of local conformational degrees of freedom due to the associated solvent rather than from a partial chain collapse which onsets as attractive solvent content is decreased.