Statistical thermodynamics evaluation of polymer-polymer miscibility

The Simha and Somcynsky (S-S) statistical thermodynamics theory was used to compute the solubility parameters as a function of temperature and pressure [delta = delta(T, P)], for a series of polymer melts. The characteristic scaling parameters required for this task, P*, T*, and V*, were extracted from the pressure-temperature-volume (PVT) data. To determine the potential polymer-polymer miscibility, the dependence of delta versus T (at ambient pressure) was computed for 17 polymers. Close proximity of the delta Versus T curves for four miscible polymer pairs: PPE/PS, PS/PVME, and PC/PMMA signaled the usefulness of this approach. It is noteworthy, that the tabulated solubility parameters (derived from the solution data under ambient conditions) propounded the immiscibility of the PVC/PVAc pair. The computed values of delta also suggested miscibility for polymer pairs of unknown miscibility, namely PPE/PVC, PPE/PVAc, and PET/PSF. In recognizing the limitations of the solubility parameter approach (the omission of several thermodynamic contributions), these preliminary results are auspicious because they indicate a new route for estimating the miscibility of any polymeric material at a given temperature and pressure. (C) 2004 Wiley Periodicals, Inc.