The cloud point curves of upper and lower consolute solution temperatures have been determined for polydispered polymethyl methacrylate (PMMA) solutions of n-butyl chloride and characterized in terms of entropic parameters of Flory-Huggins' theroy.
Depending on the rate of heating or cooling processes, the clouding points of the atactic polydispersed PMMA - n-butyl chloride solutions, determined by the visible light absorption, vary abruptly near the extremum points. The equilibrium curves were approximated from the clouding points of zero rate by extrapolation.
The equilibrium curves of the upper consolute polymer solutions having different molecular weights, shift to lower temperature regions as molecular weight decreases, while the lower consolute points appears at higher temperature. Further the shapes of phase boundaries near the consolute solution points become flattened and scattered at both temperature regions. The polymer solutions with bimodal molecular weight distribution were also found to have the small curvatures near the extrimum points, representing the influence of the polydispersity.
Near the consolute solution points, the effect of polydispersity was characterized with the use of the Flory-Huggins' entropic parameters from the clouding point curves. Compared with the polymer solutions of the unimodal distribution, the PMMA solutions with the bimodal distribution have a large increase in entropic parameter, representing the entropic effect of size dissimilarity.