Studies of polymer–polymer solubility using a two-dimensional solubility parameter approach

The two-dimensional solubility parameter approach has been applied to the prediction of solubility of one polymer in another. The solubility parameters of a number of polymers have been calculated and the second dimension shown to improve the agreement between the calculated solubility and that measured using a ternary solution technique. The method proved most useful for predicting the effect of small structural modifications on solubility, and several examples of changing solubility, monitored by calculations and measurements, are given. Structural modifications included copolymer ratio variations and substitutions to affect polymer density or reduce polarity of functional groups. The effects of temperature and molecular weight on solubility are discussed in terms of regular solution theory, which could not account for the decrease in solubilities with increased temperature observed for several polymer–polymer systems.