Based on the lattice model of random polymer solution

a new molecular thermodynamic model for describing the swelling behavior of temperature and pH-sensitive random copolymer gels was developed.This model considers three contributions of chemical potential:mixing of different polymer and solvent

elasticity of polymer network

and ionic effect with Donnan equilibrium of ions distributed inside and outside gels and electrostatic interactions between the charges carried by polymer network and counter ions.Compared with other models

this model considers the composition of two polymers f.Two kinds of model parameters are included

which are the interaction energy parameters between polymer network and solvent ???

and a size parameter

which is the molecular weight of the network between two cross-linking points Mc.The results show that this model can describe the swelling behavior of temperature and pH-sensitive random copolymer gels by using fewer model parameters.