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 C-60 moieties at predetermined positions via the combination of atom transfer radical polymerization (ATRP) and click chemistry. Azide-containing polymer precursors including monoazide-terminated and alpha,alpha-diazide-terminated poly(N-isopropylacrylamide), N-3- PNIPAM and (N-3)(2)-PNIPAM, as well as poly(ethylene glycol)-b-PNIPAM with one azide moiety at the diblock junction, PEG(-N-3)-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 C in the presence of glycine afforded alkynyl-modified C-60, alkynyl-C-60. Subsequently, the click reaction of N-3-PNIPAM, (N-3)(2)-PNIPAM, and PEG(-N-3)-b-PNIPAM led to the facile preparation of thermoresponsive diblock copolymer and homopolymers functionalized with controlled numbers of C-60 at designed positions, including C-60-PNIPAM, (C-60)(2)-PNIPAM, and PEG(-C-60)-b-PNIPAM. All the intermediate and final products were characterized by H-1 NMR, Fourier transform infrared spectroscopy (FT-IR), UV-vis spectroscopy, thermogravimetric analysis (TGA), and gel permeation chromatograph (GPC) equipped with UV/RI dual detectors. C-60-containing hybrid nanoparticles were then fabricated via supramolecular self-assembly of C-60-PNIPAM, (C-60)(2)-PNIPAM, and PEG(-C-60)-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.