Tailoring the Temperature-Induced Phase Transition and Coacervate Formation of Methylated β-Cyclodextrins-Threaded Polyrotaxanes in Aqueous Solution

Polyrotaxanes (PRXs) composed of threading methylated cyclodextrins exhibit a temperature-dependent reversible phase transition across the lower critical solution temperature (LCST) in water. In this study, a variety of methylated β-cyclodextrin (β-CD)-threaded PRXs (Me-PRXs) with different number of methyl groups modified on the β-CD and with different compositions of axle polymers (i.e., Pluronic, PEG-b-PPG-b-PEG) were synthesized, and the relationship between the LCST value and structural parameters was investigated. The LCST values of the Me-PRXs decreased with an increasing the methylation degree of the threading β-CD. Differential scanning calorimetric measurements demonstrated that the temperature-induced phase transition of the Me-PRXs occurred due to the dehydration of the threading methylated β-CD moieties and the subsequent hydrophobic interactions. Interestingly, the Me-PRXs formed coacervate droplets above their LCST. Altogether, we concluded that the LCST values of the Me-PRXs varied according to their structural parameters and could be applied as temperature-responsive biomaterials or therapeutics.