Synthesis of UCST-Responsive PMAGA for the Design of Surface-Grafted Hydrogels

We report for the first time the fabrication of thermoresponsive poly( N -methacryloyl glycinamide) (PMAGA) thin hydrogel films and micropatterned structures, providing a simple and versatile platform for UCST-based materials engineering. The steps consist of a straightforward synthesis and purification of the monomer N -methacryloyl glycinamide (MAGA), followed by its conventional radical copolymerization with allyl methacrylate (AMA), allowing the incorporation of 0.5–5.0 mol % of AMA. The resulting purified PMAGA-based copolymers exhibited upper critical solution temperature (UCST) behavior in water, with a transition temperature below 20 °C at varying polymer concentrations (2–5 wt %). Surface-attached hydrogel films were synthesized by cross-linking and grafting ene-functionalized PMAGA on thiol-modified substrates through a thiol–ene click reaction. This cross-linking and grafting (CLAG) strategy yielded homogeneous films with well-controlled dry thicknesses ranging widely from a few nanometers to a few micrometers. The hydrogel films were characterized in air and water by atomic force microscopy and ellipsometry. Using the UV-induced thiol–ene reaction, well-defined patterns were also designed via the conventional photolithography technique with photomasks. The swelling of PMAGA surface-attached hydrogel films and patterns underwater was investigated as a function of temperature. All of the grafted hydrogels exhibited UCST behavior in water, opening opportunities for the use of PMAGA hydrogels in biotechnology applications.