Spectroscopic characterization of mixed siloxane-oxide systems

We can say that until about 1960 most of the mixtures that were known to have LCST behavior were polar, often interacting through the formation of hydrogen bonds, and in these systems it was recognized that the transition was related to entropy changes that are a result of association. Which of these effects, free volume or association, will dominate in mixtures and solutions of polymers that hydrogen bond? In order to address this question we have applied the Sanchez-Lacombe model. Following Sanchez's methodology, we have formally derived a partition function for a hydrogen bonding polymer blend that includes equation of state effects. We will present a single example, a blend of poly(vinyl phenol) with poly(butyl methacrylate). For this system we have calculated the phase behavior using the spinodal condition and have also calculated the spinodal using our original model without the equation of state effects.