Synthesis and thermally-triggered self-assembly behaviors of a dumbbell-shaped polymer carrying β-cyclodextrin at branch points

We report the design and synthesis of a thermally-responsive dumbbell-shaped polymer based on one β-cyclodextrin (β-CD)-terminated polyethylene glycol (PEG) segment and several poly(N-isopropylacrylamide) (PNIPAM) segments through combining click reaction with atom transfer radical polymerization. Thermally-triggered self-assembly and molecular inclusion behaviors of the polymer were investigated by UV-vis spectroscopy, dynamic light scattering (DLS), 1H NMR in D2O, fluorescence spectroscopy and transmission electron microscopy. These results indicated that the polymer presents both thermal sensitivity and molecular inclusion properties due to the existence of PNIPAM segments and β-CD units. Above the lower critical solution temperature (LCST) of PNIPAM segment, the polymer can self-assemble into nano-sized assemblies, where PNIPAM segments serve as the core and PEG segments are organized as the corona. By using 1-adamantane acid sodium as guest molecule, the polymer shows size-adjusted aggregation behaviors based on the inclusion interactions between β-CD and guest molecule.