Using the histogram Monte Carlo simulation method and the bond-fluctuation model, I investigate the coil-globule collapse transition of a macromolecular chain under variable solvent conditions. The critical transition temperature (Theta-point) is accurately determined. Finite-size scaling results near the transition point are verified. Furthermore, the first-order transition associated with the freezing/crystallization of a polymer at a temperature below the Theta-point is also observed. The free energy profiles associated with these two transitions are explicitly computed.
