A computational investigation of the critical condition used in the liquid chromatography of polymers


The partitioning of a self-avoiding walk chain into a square channel with different surface interaction ε w has been examined using lattice Monte Carlo simulation in order to have a better understanding of the critical condition used in the liquid chromatography. The partition coefficient, K, of the self-avoiding walk chain in a square channel at the critical adsorption point determined earlier was found to vary dramatically with the chain length when the channel width is comparable to or smaller than the chain sizes. As a result, the critical condition point relevant to the experiments cannot be defined as the critical adsorption point. Instead, the critical condition point, which is best defined as the point at which K varies least with the chain length, in the same spirit of experimental studies, can be identified clearly when the standard deviation of In K, σ(ln K) for the given range of chain length, is plotted against the ε w. The critical condition point thus found, ε w∝, was more attractive than the critical adsorption point in the channel. The narrower the channel is, the more attractive the surface interaction would be at the critical condition point. In a slit pore, however, the critical condition point does not shift and remains at the critical adsorption point regardless of the slit width. The phenomenon observed in the square channel is found to be consistent with earlier experimental results.

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