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

Abstract

SUMMARY: A polyrotaxane in which many b-cyclodextrins (b-CyDs) 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. bCyDs threaded onto the triblock copolymer enhance the solubility of the polyrotaxane and presumably contribute to the prevention of aggregation between PPG segments. The interaction of b-CyDs with a terminal FITC moiety was observed to be significant at 10 8C, however, with increasing temperature, the interaction of b-CyDs with a PPG segment becomes prominent. From these results, it is concluded that the majority of bCyDs move toward the PPG segment with increasing temperature although some b-CyDs may reside on PEG segments.

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

“…Moreover, for these b-CD-derived PRs, as reported previously, b-CD can selectively form ICs with PEG block or PPG block, although the majority of b-CDs move toward the PPG segment with increasing temperature, and some b-CDs may still reside on PEG segments. 17,25 According to the aforementioned results, when b-CDs reside on the PEO blocks of Pluronic F127, 28,29 the structure of the IC formed by b-CDs and PEO blocks is similar to that of b-CDs and PPG IC, so no more exact judgment whether the b-CDs stay on the PPG block or the PEO blocks can be given here.…”

“…This was well consistent with the previous reports. 17,25 CONCLUSIONS A kind of novel main-chain polyrotaxanes has been prepared via the ATRP of HPMA initiated with polypseudorotaxanes made from a-or b-CDs self-assembly with a distal 2-bromoisobutyryl end-capped Pluronic F127 in the presence of Cu(I)Br/PMDETA at 25 8C in aqueous media. All the GPC traces exhibited a narrow molecular weight distribution with a polydispersity index of 1.26-1.42 for the a-CD-and 1.41-1.84 for b-CD-derived PRs, respectively.…”

“…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.…”

Cooperative threading of asymmetric rings onto a linear chain

“…[3,7] Recent results with b-CD PEG/PPG/PEG polyrotaxanes seem to show that precipitation is not essential for b-CD to gather on the PPG segment. [9] However, this assembling/dispersing behavior, inferred from the optical properties of the end groups (stoppers), is just opposite to what the solubility indicates: [2] the assembling occurs on heating and not on cooling. Quite naturally, the question of the role of end groups in the whole process arises.…”

Effects of several inter-molecular interactions on the inclusion between methyl substituted β-cyclodextrin and some linear macromolecule in supercritical carbon dioxide medium

“…In most cases, the inclusion between cyclodextrin and polymer in aqueous solution was investigated [1][2][3][4][5][6][7][8][9][10], recently this investigation was focused on the selective inclusion between cyclodextrin and some block polymers [11][12][13][14][15][16][17][18][19][20]. In aqueous solution, the hydrophobic interaction between the cyclodextrin cavity and the hydrophobic part of the polymer chain is the main driving force; the molecular recognition between the host and the guest determined the extent of the complex; and the length of the polymer dominated the fraction of coverage for the polymer by the cyclodextrin rings in the complex.…”