Using Click Chemistry To Fabricate Ultrathin Thermoresponsive Microcapsules through Direct Covalent Layer-by-Layer Assembly

Abstract

We report the syntheses of azido- and acetylene-functionalized poly(N-isopropylacrylamide) (PNIPAm) copolymers and their use in the fabrication of ultrathin thermoresponsive microcapsules through direct covalent layer-by-layer (LbL) assembly using click chemistry. The clickable copolymers poly[N-isopropylacrylamide-co-(trimethylsilyl)propargylacrylamide] and poly(N-isoropylacrylamide-co-3-azideopropylacrylamide) were prepared through atom transfer radical polymerization (ATRP) at 0 °C using a synthesized dansyl-labeled initiator and the CuBr/Me6TREN (hexamethylated tris[2-(dimethylamino)ethyl]amine) catalyst complex in 2-propanol. After removing the protective trimethylsilyl groups, these clickable PNIPAm copolymers assemble alternately onto azido-modified silica particles in aqueous media through click reactions catalyzed by copper sulfate and sodium ascorbate. After removing the template, the microcapsules remained stable because of the presence of the covalently bonded triazole units; the microcapsules...