title: Thermosensitive hybrid hydrogels with silica nanoparticle-cross-linked polymer networks.
abstract: A simple methodology for the preparation of thermosensitive organic-inorganic hybrid hydrogels using silica nanoparticle-mediated polymer networks is described. A thermosensitive copolymer poly[N-isopropylacrylamide-co-(3-methacryloxypropyltrimethoxysilane)], (pNS), with reactive side chains (Si-O-CH3) was first synthesized by free radical polymerization using N-isopropylacrylamide (NIPAAm) and 3-methacryloxypropyltrimethoxysilane (MAPTS). Then, simple mixing of the aqueous solution of this copolymer with silica nanoparticle (SiP) suspensions at room temperature led to the formation of thermosensitive hybrid hydrogels cross-linked with silica nanoparticles (SiP) which did not require any other processing like washing for the removal of unreacted monomers and initiators. The effects of SiP content on gelation abilities, temperature-responsive behaviors, swelling and deswelling kinetics, and mechanical properties of the hydrogels were investigated. The results showed that transparent hybrid hydrogels with adjustable network structures were obtained within a few minutes to a couple of hours depending on the concentration of the copolymers and the silica nanoparticles. The hybrid hydrogels exhibited a lower critical solution temperature (LCST) of around 33 °C with no significant deviation from conventional poly(N-isopropylacrylamide) hydrogels; the LCST was not significantly affected by the concentration of silica nanoparticles (which in these systems serve as the cross-linkers). In addition, the hydrogels showed significantly large equilibrium swelling ratios, improved mechanical strength, and suitable deswelling behavior, which can easily be tuned by varying the composition of the hybrid hydrogels.
authors.affiliation: Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1, Kurokami, Kumamoto 860-8555, Japan. ashraf.nstu@yahoo.com
authors.forename: Md
authors.initials: M
authors.lastname: Ashraful Alam
authors.forename: Makoto
authors.initials: M
authors.lastname: Takafuji
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Ihara
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D001672:Biocompatible Materials / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003432:Cross-Linking Reagents / Q000737:chemistry; D004867:Equipment Design; D020100:Hydrogels / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology; D011108:Polymers / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D013696:Temperature
chemical_list: D000180:Acrylic Resins; D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D020100:Hydrogels; D011108:Polymers; C052970:poly-N-isopropylacrylamide; D012822:Silicon Dioxide