Formation of Isolated Pseudo-Polyrotaxane Nanosheet Consisting of α-Cyclodextrin and Poly(ethylene glycol)

Nanosheet materials have recently attracted the attention of researchers because of their unique physical properties. In the present study, we have reported a novel methodology to fabricate isolated nanosheet materials, called pseudo-polyrotaxane (PPR) nanosheets, which are formed by biocompatible complexation between α-cyclodextrin (CD) and poly(ethylene glycol) (PEG) for the first time. When the molecular weight of axis PEG was changed in the range between 2k and 6k, isolated PPR nanosheets were obtained with thicknesses ranging from 14.6 to 33.8 nm, depending on the axis PEG length. We found that uncovering the axis ends led to the formation and isolation of PPR nanosheets when the binding constant between the axis ends and α-CD was changed. Additionally, the PPR structures consisting of multiarm PEG indicated that the uncovered parts of the axis near the branched point also promoted the formation of isolated PPR nanosheets. Uncovering the parts of the axis polymer is essential for fabricating the isolated PPR nanosheets because the uncovered parts of the axis suppress the crystal growth of α-CD in the axis direction and results in the isolation of PPR nanosheets.