Journal of Chemical Physics, Vol.105, No.2, 802-809, 1996
Chain-Length Dependence of the Polymer-Solvent Critical-Point Parameters
We report grand canonical Monte Carlo simulations of the critical point properties of homopolymers within the bond fluctuation model. By employing configurational bias Monte Carlo methods, chain lengths of up to N=60 monomers could be studied. For each chain length investigated, the critical point parameters were determined by matching the ordering operator distribution function to its universal fixed-point Ising form. Histogram reweighting methods were employed to increase the efficiency of this procedure. The results indicate that the scaling of the critical temperature with chain length is relatively well described by Flory theory, i.e., Theta-T-c similar to N--0.5. The critical volume fraction, on the other hand, was found to scale like phi(c) similar to N--0.37, in clear disagreement with the Flory theory prediction phi(c) similar to N--0.5, but in good agreement with experiment. Measurements of the chain length dependence of the end-to-end distance indicate that the chains are not collapsed at the critical point.
Keywords:UNIVERSAL COEXISTENCE CURVE;MONTE-CARLO SIMULATIONS;CRITICAL-BEHAVIOR;THETA-POINT;CRITICAL EXPONENTS;PHASE-TRANSITIONS;FREE-ENERGY;MIXTURES;FIELD;CROSSOVER