Predicting solubilities of vinyl polymers

Accurate solubility limits of polymers are best expressed by molecular weight fractionation curves. Individual curves may be obtained for each polymer–solvent (–nonsolvent) system. A method for predicting solubility behavior, based on solubility parameter δ and hydrogen bonding index γ, is proposed here. The correlation is of the form\documentclass{article}\pagestyle{empty}\begin{document}$\left[\eta \right] = k\frac{{T^{\left( {cQ} \right)} }}{{\left( {v.f} \right)^{\left( {ab + R} \right)} }}$\end{document} where [η] = intrinsic viscosity of precipitated polymer; T = absolute temperature; ( v.f. ) = volume fraction of solvent; R = (δ s − δ n ) − 0.3(γ s − γ n ); Q = (γ p − γ e ) 2.2 /(δ p − δ e ); p refers to polymer; s refers to solvent; n refers to nonsolvent; e refers to solvent system at theta temperature; and a , b , c , and k are fitted constants. The correlation was derived from data for poly(vinylpyrrolidone) and polyacrylamide. It probably is limited to systems in which the precipitate occurs as a liquid.