Click Coupling Fullerene onto Thermoresponsive Water-Soluble Diblock Copolymer and Homopolymer Chains at Defined Positions

We report on the synthesis of well-defined thermoresponsive water-soluble diblock copolymer and homopolymers functionalized with controlled numbers of C60 moieties at predetermined positions via the combination of atom transfer radical polymerization (ATRP) and click chemistry. Azide-containing polymer precursors including monoazide-terminated and R,R-diazide-terminated poly(N-isopropylacrylamide),N3PNIPAMand (N3)2-PNIPAM, as well as poly(ethylene glycol)-b-PNIPAMwith one azidemoiety at the diblock junction, PEG(-N3)-b-PNIPAM, were synthesized via ATRP using specific azide-functionalized small molecule and polymeric initiators. On the other hand, the reaction of 4-prop-2-ynyloxybenzaldehyde with pristine C60 in the presence of glycine afforded alkynyl-modified C60, alkynyl-C60. Subsequently, the click reaction of N3-PNIPAM, (N3)2-PNIPAM, and PEG(-N3)-b-PNIPAM led to the facile preparation of thermoresponsive diblock copolymer and homopolymers functionalized with controlled numbers of C60 at designed positions, including C60-PNIPAM, (C60)2-PNIPAM, and PEG(-C60)-b-PNIPAM. All the intermediate and final products were characterized by H NMR, Fourier transform infrared spectroscopy (FT-IR), UV-vis spectroscopy, thermogravimetric analysis (TGA), and gel permeation chromatograph (GPC) equipped with UV/RI dual detectors. C60-containing hybrid nanoparticles were then fabricated via supramolecular self-assembly of C60-PNIPAM, (C60)2-PNIPAM, and PEG(-C60)-b-PNIPAM in aqueous solution, which were characterized by dynamic and static laser light scattering (LLS) and transmission electron microscopy (TEM). These novel fullerenated polymers retain the thermoresponsiveness of PNIPAM-based precursors, and self-assembled hybrid nanoparticles exhibit thermo-induced collapse/aggregation behavior due to the lower critical solution temperature (LCST) phase transition of PNIPAM chains.