title: Thermoresponsive nanohydrogels cross-linked by gold nanoparticles.
abstract: Thermoresponsive nanohydrogels cross-linked by gold nanoparticles (AuNPs) were prepared by 1,3-dipolar cycloaddition reactions and in situ reversible addition-fragmentation chain-transfer (RAFT) polymerization. In order to synthesize thermoresponsive nanohydrogels, AuNPs decorated with azide groups (AuNPs-N(3)) were prepared through ligand exchange. Click reactions between AuNPs-N(3) and dialkynetrithiocarbonate yielded cross-linked AuNP aggregates. The size and cross-linking density of AuNP aggregates increased with the molar ratio of acetylene groups to azide groups. After click reactions, the absorption maximum of the plasmon band of AuNPs red-shifted to a long wavelength. Thermoresponsive nanohydrogels were prepared by in situ RAFT polymerization of N-isopropylacrylamide (NIPAM) using trithiocarbonate in the cross-linked AuNP aggregates as chain-transfer agents. The thermoresponsive nanohydrogels presented a low critical solution temperature at around 32 degrees C due to the "coil-to-globule" transition of connecting PNIPAM chains in the nanohydrogels. The size of the thermoresponsive nanohydrogels was determined by the molar ratio of acetylene groups to azide groups.
authors.affiliation: Key Laboratory of Functional Polymer Materials, Ministry of Education, Department of Chemistry, Nankai University, Tianjin 300071, People's Republic of China.
authors.forename: Xueming
authors.initials: X
authors.lastname: Lian
authors.forename: Jie
authors.initials: J
authors.lastname: Jin
authors.forename: Jia
authors.initials: J
authors.lastname: Tian
authors.forename: Hanying
authors.initials: H
authors.lastname: Zhao
mesh_terms: D003432:Cross-Linking Reagents / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D053768:Metal Nanoparticles; D036103:Nanotechnology / Q000379:methods*; D011108:Polymers / Q000737:chemistry; D013696:Temperature; D013871:Thiones / Q000737:chemistry; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D003432:Cross-Linking Reagents; D011108:Polymers; D013871:Thiones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D006046:Gold; C013321:trithiocarbonic acid