Theoretical determination of the theta temperature for solvent-polymer systems

The miscibility behavior of five binary polymer-solvent systems was studied by means of the Flory-Huggins theory. The theta temperature and the entrop ic and energetic Flory-Huggins parameters were calculated for these systems . The coordination number in the Flory-Huggins model and the interaction en ergy parameters were determined using a molecular simulation technique base d on a Monte Carlo approach, which takes into account the constraints assoc iated with excluded volume. In all cases, the critical temperature (T-c) va lues were calculated and compared with the experimental data. Thermodynamic parameters were obtained by plotting 1/T-c versus (1/x/(1/2)(2) + 1/2x(2)) curve, where x(2) is the degree of polymerization. This study shows a furt her application of the Flory-Huggins theory combined with molecular simulat ion techniques, for the model parameter determination, which was previously proposed by C.F. Fan, B.D. Olafson, M. Blanco, Macromolecules 25 (1992) 36 67. In addition, the limitations of the methodology proposed by C.F. Fan, B .D. Olafson, M. Blanco, Macromolecules 25 (1992) 3667, for miscibility calc ulations of binary polymer systems, are further discussed with special atte ntion given for the model parameter determination. (C) 1999 Elsevier Scienc e B.V. All rights reserved.