Covalent Functionalization of Single-Walled Carbon Nanotubes with Thermoresponsive Core Cross-Linked Polymeric Micelles

A facile method for the covalent functionalization of single-walled carbon nanotubes (SWNTs) with thermoresponsive core cross-linked (CCL) polymeric micelles is presented. This method is based on SWNT functionalization as well as polymer self-assembly. The copolymer, poly( N,N -dimethylacrylamide)-b-poly(N-isopropylacrylamide-co-N-acryloxysuccinimide) (PDMA-b-P(NIPAM-co-NAS)), bearing an azide group at the PDMA end, was first prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization. Covalent functionalization of SWNTs with well-defined, azide-derivatized PDMA-b-P(NIPAM-co-NAS) was then accomplished by a nitrene addition reaction. The copolymer-functionalized SWNTs (f-SWNTs) consisted of about 26 wt % copolymer and exhibited relatively high solubility in water. Subsequently, the coassembly of the copolymer and f-SWNT blends was carried out in aqueous solution. It was found that the copolymer chains grafted onto the surface of SWNTs were coassembled with the free chains in solution, leading to thermoresponsive polymeric micelles that adhered to the surface of nanotubes. Upon cross-linking, the copolymer aggregates were stabilized and covalently anchored to SWNTs (SWNT-micelle). The resulting assembled nanostructures were still soluble in water and were characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM).