Thermally Induced Localization of Cyclodextrins in a Polyrotaxane Consisting of β-Cyclodextrins and Poly(ethylene glycol)−Poly(propylene glycol) Triblock Copolymer

Abstract

A polyrotaxane, in which many β-cyclodextrins (β-CDs) are threaded onto a triblock copolymer of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG) capped with fluorescein-4-isothiocyanate (FITC), was synthesized as a model of stimuli-responsive molecular assemblies for nanoscale devices. Coupling of FITC with the terminal amino groups in the polypseudorotaxane was performed in DMF at 5 °C. Under these conditions, a side reaction between the hydroxyl groups of β-CD and FITC was prevented. The interaction of the β-CDs with terminal FITC moieties in the polyrotaxane was significantly observed at low temperature. However, the interaction of the β-CDs with the PPG segment was observed with increasing temperature. On the basis of these results, it is concluded that the majority of the β-CDs move toward the PPG segment with increasing temperature although some β-CDs may reside on the PEG segments.

Novel main‐chain polyrotaxanes synthesized via ATRP of HPMA in aqueous media

“…(6)H of b-CD in the PR were obviously broadened and somewhat shifted to the downfield due to the decrease in conformational flexibility after forming a polyrotaxane. As reported previously, 17 the methyl proton peak of Pluronic F127 should shift to the lower field and broadened upon a PR formation. In fact, because the methyl proton peak of Pluronic F127 located at 1.00-1.06 ppm was somewhat superposed with that of the end CH 3 of PHPMA located at 1.09 ppm, these down-shift and broadening were not clearly observed, but as compared with the a-CDderived PRs whose corresponding proton resonance peaks at 1.02-1.04 and 1.09-1.12 ppm were well separated each other, it could be judged that the methyl proton peak of Pluronic F127 was broadened.…”

“…With the intriguing characteristics of free sliding and/or rotating of the threaded cyclic molecules, the polyrotaxanes have attracted increasing interests for their potential applications in smart materials, for example, stimuliresponsible supramolecular hydrogels, 4 slide-ring gels, 5,6 molecular machines, 7 carriers for drug delivery with hydrolysable bulky ends, 8 energy-transfer systems with modified CDs, 9 pH-/temperature-sensitive supramolecular micelles 10 and insulated molecular wires. 11 As for their preparation, a wide variety of strategies have been developed, [12][13][14] with a number of bulky groups such as naphthyl, 15 trinitrophenyl, 16 fluorescein-4-isothiocyanate 17 and 9-anthryl groups as the end stoppers. 18 However, oligomers or polymers of vinyl monomers have been rarely exploited as end stoppers of main-chain polyrotaxanes to our knowledge, 19,20 especially to do so via the atom transfer radical polymerization (ATRP).…”

“…The driving force for such an inclusion complexation or self-assembly of CDs with a linear polymer chain is due to the intermolecular hydrogen bondings between neighboring CDs as well as steric fittings and the hydrophobic interaction between host and guest molecules. 1,24 However, these intermolecular forces such as hydrogen bondings between neighboring CDs and/ or the hydrophobic interaction would be eliminated in such a kind of polar aprotic solvents, 17,25 leading to the threaded CDs sliding off the polymeric chain sig-nificantly. Therefore, the ATRP undergone in aqueous media would afford not only the advantage to impede the dethreading of CDs during the process but also a new concept to improve the functions of the currently available polyrotaxanes for smart materials.…”

Self-assembled Structure of Polyrotaxane Consisting of β-Cyclodextrin and Poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) Triblock Copolymer in Bulk System

“…17 More recently, switching of the location of CDs along the polymer axis has been performed by changing temperature. 18,19 Thus, it seems that polyrotaxanes made by CDs are one of the best supramolecular polymer systems to tune the self-assembled structure by changing the preparative pathway.…”

Formation of Superstructure Composed of Modified Cyclodextrins as Molecular “Blocks” in Aqueous Solution with Host-Guest Complexation. Correlation of Chemical Structure of Modified Group with Complexation

“…2 Some superstructures that incorporate plural CDs as components have been reported as pseudoroxanes, rotaxanes, polyrotaxanes, 3 side-chain polyrotaxanes, 4 catenanes, 5 and molecular shuttle driven by light 6 or heat. 7 A rather unique superstructure has been observed in the solid state for a monosubstituted [3-CD derivative that behaves as host and guest, such that bulky hydrophobic groups intermolecularly enter other CD cavities and helical "polymers" are formed 8 or such that a -CH2-NH(CH2)6NH2 side chain on the primary face of one molecule enters a cavity of the f3 -CD ring of a neighboring molecule. 9 To compose a more organized system using simply modified CDs, the important factor is the combination of "flexible" groups and "rigid" groups.…”