Predictions of thermoreversible volume phase transitions in copolymer gels by lattice-fluid-hydrogen-bond theory

Certain copolymeric hydrogels such as poly(N-ispropylacrylamide)/poly(acrylic acid) show first-order volume phase transition on heating. By using the lattice-fluid-hydrogen-bond theory we have shown earlier that both hydrogen bonding interactions and hydrophobic interactions are responsible for this behavior in homopolymer gels. In this paper we demonstrate that the transition temperature of copolymer gels can be varied by changing the ratio of the two monomer concentrations in the copolymerization and also by slightly varying the hydrophobic nature of the gels. Thus it might be possible to "tailor-make" gels with desired transition temperatures. Such gels can find novel applications in biotechnology, soft robotics, separations, and sensors