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Super porous organic-inorganic poly(N-isopropylacrylamide)-based hydrogel with a very fast temperature response
Authors:B. Strachotová  ,A. Strachota,M. Uchman,M. &Scaron  louf,J. Brus,J. Ple&scaron  til,L. Matějka
Affiliation:Department of Polymer Networks and Mechanical Properties, Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovskeho nam. 2, CZ-162 06 Prague, Czech Republic
Abstract:Porous organic-inorganic (O-I) hydrogels showing a very fast temperature response, including very fast reswelling were prepared: only 6 s are needed for 72% deswelling (gel collapse) as well as for 72% reswelling. Both deswelling and reswelling are practically complete in 14 s. The gels were prepared from N-isopropylacrylamide (NIPA), N,N′-methylenebisacrylamide (BAA) and tetramethoxysilane (TMOS) by simultaneous radical polymerization and hydrolytic polycondensation of TMOS. The syntheses were carried out at temperatures below the lower critical solution temperature (LCST) of poly(NIPA) in two steps: during the first stage the temperature was held at T = +15 °C and during the second the temperature was lowered below the freezing point of the reaction mixture, T = −18 °C. The ice crystals, which grew during the second stage, served as the pore-forming agent. The best samples were obtained if the second stage was started shortly before the gel point of the reaction mixture. The introduction of the inorganic phase (silica) is necessary for the ability of fast reswelling and also results in a strong improvement of the hydrogels' mechanical properties, while the maximum swelling degree remains nearly unaffected.
Keywords:Thermoresponsive porous hydrogel   N-Isopropylacrylamide   Organic-inorganic hybrid
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