Kinetic Improvement of the Gel-sol Transition of Thermoresponsive Hydrogels Utilizing a High Surface Area Host AITranslate

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DOI：https://doi.org/10.1021/acsapm.2c02176

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Rapid reversible phase transitions of biocompatible thermoresponsive sealants (TRS) upon cooling are required for their practical application in many sectors. The gel–sol transition rate of the TRS studied here [poly(N-isopropylacrylamide-co-butyl acrylate 95:5, number-averaged molecular weight = 7–64 kg mol–1] after being heated to 50 °C is slowed dramatically. The unheated materials return to a free-flowing sol form in a matter of minutes, while the heated materials remain in a gel or solid form for hours. The gel–sol transition of these polymers is enhanced in the presence of a high surface area host in the form of open-cell foams such as polyurethane (PUR), polyimide (PIM), hydrophilic polyurethane Aquazone (AQZ), and neoprene (NEO). An enhanced rate of sol formation on cooling and high TRS recovery (74–99%) were observed across a range of foam types and pore sizes when compared to samples stored without a host (9% recovery). Polyurethane demonstrates the greatest increase in TRS recovery (∼10-fold) after storing the TRS solution at 50 °C followed by cooling for 10 min at 0 °C, maintaining the thermally reversible gelation and mechanical strength of the TRS. Crucially, rheological measurements demonstrate that the viscosity, storage modulus, and loss modulus are not significantly affected by storage in a foam host. This work may be potentially extended to other injectable in situ forming hydrogels, which have suitable mechanical strength but less ideal phase transition times.