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 α,α-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 60 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 1 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. 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.