Thermodynamic predictions of volume changes in temperature-sensitive gels. 1. theory

This paper presents a molecular theory of swollen gels based on a compressible lattice model. The theory extends the Sanchez and Lacombe lattice-fluid model for polymer solutions through addition of the elastic term of the Flory-Rehner theory of rubber swelling. The characterization of this type of binary mixture requires knowledge of pure component parameters and an interaction energy correction characteristic of each binary mixture. The four basic types of liquid-gel phase diagrams predicted are related to the presence of upper and lower consolute temperatures or closed immiscibility loops in solution of the uncross-linked Polymer.