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Session E30 - Computer Simulations & Theory II.
MIXED session, Tuesday morning, March 19
Room 265, America's Center
Recent theoretical attempts to explain the SANS \chi-parameters and phase behavior of binary blends of random copolymers of ethylene, propylene, and 1-butene have modeled the components as linear chains which differ only in their backbone stiffness. Previous simulation and PRISM studies of this semi-flexible chain model in the athermal limit have shown that entropic effects do not dominate the thermodynamics of real polyolefin blends but, instead, phase separation must be driven by a coupling between the conformational disparity and enthalpic interactions. Here we present the results of off-lattice Monte Carlo simulations of blends with symmetric dispersive interactions in addition to their stiffness asymmetry. The simulations feature a novel technique for evaluating the chemical potential of polymer chains as well as several advanced techniques for determining phase diagrams. The effect of stiffness disparity and chain length on the phase diagrams and Flory-Huggins \chi-parameters will be presented. We will also show phase diagrams for semi-flexible chains in solution.