Modeling of the phase equilibria of polyisobutylene in diisobutylketone with molecular mechanics

A method of calculating interaction parameters used in phase equilibrium calculations has been extended for predicting solvent activities of polymer solutions. A pair of interaction parameters are determined by calculating interaction energies between all pairs of molecules in the solution of interest with a molecular mechanics method known as the consistent force field (CFF). The conformational space of a pair of molecules is sampled with a Monte Carlo algorithm followed by energy minimizations. In this paper, the method is used to calculate interaction parameters and solvent activities for the diisobutylketone/polyisobutylene system, using 2,2,4-trimethylpentane as a model compound for the polymer molecule.