Phase behavior of a high-concentration sulfobetaine zwitterionic polymer solution

The phase behavior of a high-concentration solution of as-prepared sulfobetaine zwitterionic polymer solution, poly(3-dimethyl(methacryloyloxy-ethyl)ammonium propane sulfonate betaine (polySBMA) synthesized via radical solution polymerization was investigated utilizing ultraviolet–visible analytical techniques. The solution exhibited a stably reversible phase transition between transparency and opacity. The transition temperature decreased with increasing polymer concentration, in contrast to the phase behaviors of most water-soluble polymers reported in the literature. The equilibrium concentrations of the purified polySBMA with various molecular weights were further investigated. It was found that unlike most water-soluble polymers, which have low equilibrium concentrations, polySBMA had a high equilibrium concentration. In addition, the as-prepared polySBMA solution with high concentration presented an over-swelling behavior that exerted an important effect on the transition temperature of the solution. In addition, variations in the thermosensitivity of the as-prepared polySBMA hydrogels with various concentrations of crosslinking agent were investigated, confirming the conclusion stated above. Therefore, the temperature-dependent phase transition of the as-prepared polySBMA solution could be controlled by adjusting the concentration of the monomer SBMA or the crosslinking agent to make it suitable for biomedical uses or uses in other fields in the future.