Abstract
A single, flexible homopolymer chain undergoes a transition from an
extended self-avoiding walk coil into a compact, liquid-like globule
upon changing the solvent quality, for instance by changing the
temperature for stimuli-responsive polymers.Temperature as a control
parameter has also been used in computer simulations of the collapse transition which have been extensively performed since many years. All simulations
support the predictions of mean field theory (with possible logarithmic corrections) that this is a continuous transition. Adapting the recently proposed Wang-Landau Monte Carlo algorithm for the determination of the density of states to the bond-fluctuation polymer model we show that:
(i) There is a first order phase transition into a solid state in
the collapsed globule. In former simulations and also in experiments
this transition was masked by the glass transition of the dense globule.
(ii) Depending on the range of the attractive interaction there
are either seperate transitions coil/liquid globule/solid globule or a direct coil/solid globule transition in the thermodynamic limit. The latter case was not predicted theoretically. The vanishing of the liquid phase in the thermodynamic limit is in quantitative agreement with results on the phase
behavior of colloids with short-ranged interactions.
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