Convenient Protocol for Preparing Hydrogels with Temperature-Insensitive Swellability

Polymer gels are three-dimensional polymer networks immersed in solvents. They usually exhibit tunable elasticity and swellability that both depend on the solvent quality as a function of the temperature. The development of temperature-insensitive gels is essential in some applications such as treating retinal detachments and scaffolds for tissue regeneration, where the volume change caused by swelling and deswelling is undesirable. To this end, it is feasible to tune either the content and species of the polymer or those of the solvent. Nevertheless, the testing of the temperature dependence of swelling is a laborious process because the equilibration of a gel sample of approximately centimeter dimensions at one temperature can take several hours or even days. In this study, we selected a neutral tetrapoly(ethylene glycol) gel (Tetra-PEG gel) in various mixed solvents as a model system to explore the relationship between the overlap concentration of the precursor solution and the elastic shear modulus and the swelling ratio of the gel network. Our findings reveal that rheometric analysis offers an efficient approach to identifying the optimal mixed solvents, i.e., solvents with temperature-independent interactions with the polymer, to prepare gels having temperature-insensitive swellability over a wide temperature range of application.