Effect of chain stiffness on polymer phase behavior

Since intermolecular contacts increase in number as chain stiffness increases, an increase in critical temperature for the semiflexible chains over the freely-jointed chains is also expected. To resolve this issue, vapor-liquid phase diagrams of a semiflexible chain model using Monte Carlo simulation are calculated and the results are compared for similar flexible model. The combination of the chain increment and configurational-bias methods is applied to calculate the chain chemical potential. It is found that semiflexible chains have more intermolecular contacts than the fully flexible chains, consistent with previous work. They also exhibit higher volatility and high chain chemical potentials. As a result, phase envelopes of the semiflexible chains fall below and with the fully flexible counterparts. The critical point temperatures of longer semiflexible chains shifts down slightly more than chains of shorter lengths.