Lattice fluid model generalized for specific interactions: An application to ternary polymer solutions

The phase diagram of the Poly-l-Lactic-Acid (PLLA), dioxane and water system was derived by using the lattice fluid model generalized for specific interactions. A qualitative analysis of Hansen solubility parameters together with empirical observations were adopted to reduce the number of adjustable parameters. The as-selected model parameters were derived by fitting a set of cloud point curves; consequently, the complete phase diagram of the system was computed. The use of specific interactions between species gave out a quantitative agreement with a set of experimental data, whereas changing the polymer polydispersity the agreement is only qualitative. In principle, the presented procedure could be adopted for the calculation of liquid–liquid equilibria in ternary polymer solutions with similar features of PLLA–dioxane–water system.