Synthesis and characterization of a polyrotaxane consisting of beta-cyclodextrins and a poly(ethylene glycol) poly(propylene glycol) triblock copolymer

A polyrotaxane in which many beta-cyclodextrins (beta-CyDs) are threaded on to a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene g lycol) (PPG) capped with fluorescein-4-isothiocyanate (FITC) was synthesize d as a model of stimuli-responsive molecular assemblies for nanoscale devic es. beta-CyDs threaded onto the triblock copolymer enhance the solubility o f the polyrotaxane and presumably contribute to the prevention of aggregati on between PPG segments. The interaction of beta-CyDs with a terminal FITC moiety was observed to be significant at 10 degrees C, however, with increa sing temperature, the interaction of beta-CyDs with a PPG segment becomes p rominent. From these results, it is concluded that the majority of beta-CyD s move toward the PPG segment with increasing temperature although some bet a-CyDs may reside on PEG segments.