Thermoresponsive N-vinylcaprolactam-based PolyHIPE hydrogels with composition-controlled water uptake and volume phase transition behaviorMajer Kovačič, Janja (Avtor) Podgrajšek, Špela (Avtor) Kovačič, Sebastijan (Avtor) HIPE templatingthermoresponsive polymersN-vinylcaprolactamNN-dimethyl acrylamidewater uptakeswelling ratioA series of thermoresponsive polyHIPE hydrogels based on N-vinylcaprolactam (NVCL) and N,N-dimethylacrylamide (DMAA) were prepared using oil-in-oil (O/O) high internal phase emulsion (HIPE) templating to investigate how copolymer composition influences porous morphology, water uptake, and volume phase transition (VPT) behavior. HIPE stability strongly depends on the NVCL/DMAA ratio, reflecting differences in monomer polarity and partitioning. Incorporating DMAA significantly improved HIPE stability and enabled the preparation of highly porous homo- and copolymeric monoliths with porosities of 92–94%. Enhanced HIPE stability reduces the pore size in polyHIPEs, with average void diameters decreasing from approximately 92 μm in NVCL-based polyHIPEs to 23 μm in DMAA-rich polymer materials. Equilibrium water uptake at 4 °C increased significantly from approximately 2 g·g–1 for NVCL polyHIPEs to 27 g·g–1 for DMAA polyHIPEs, while NVCL-co-DMAA polymer materials showed intermediate uptakes (15–24 g·g–1) depending on composition. All NVCL-containing polyHIPEs exhibited reversible thermoresponsive behavior. Water uptake decreases upon heating to 45 °C (9–21 g·g–1) due to thermally induced network collapse, as NVCL segments exceed their lower critical solution temperature. Increasing the DMAA ratio enhances water retention and suppresses deswelling of polyHIPEs, while NVCL-rich compositions exhibit pronounced, reversible volume contraction. These results demonstrate that DMAA and NVCL have complementary roles in polyHIPE architectures. DMAA segments control hydrophilicity and water uptake, while NVCL provides thermoresponsive functionality. The combination of tunable porosity, high water absorbency, and reversible thermoresponsive behavior demonstrates their potential as a platform for temperature-responsive absorbents.ACS Publications20262026-09-16 09:08:51Članek v reviji100386UDK: 547.4COBISS_ID: 290358275DOI: 10.1021/acsapm.6c02452ISSN pri članku: 2637-6105sl© The Authors