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.