QUASICHEMICAL EQUILIBRIUM APPROACH TO CROSSLINKED POLYMER SOLUTIONS.

Thermodynamic functions for mixing of a solvent with a crosslinked (branched) polymer are derived by considering the primary chains as copolymers of crosslinked and uncrosslinked units. Primary chains and solvent molecules are placed on a lattice with coordination number z. In the polydisperse case, primary chains with a constant number of crosslinked and uncrosslinked units are taken as components. It is shown that the interaction parameter x is a function of the coordination number, degree of crosslinking, molecular weight of primary chains (and concentration); the dependence vanishes if z goes to infinity. The coefficient alpha depends on the network structure and is equal to 1/2 only for an ideal network obtained by crosslinking of an infinite primary chain.