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Effect of Alkyl Chain Length of Acylated α‐Cyclodextrin‐Threaded Polyrotaxanes on Thermoresponsive Phase Transition Behavior
Author(s) -
Tamura Atsushi,
Ohashi Moe,
Tonegawa Asato,
Kang Tae Woong,
Zhang Shunyao,
Yui Nobuhiko
Publication year - 2021
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.202000420
Subject(s) - alkyl , chemistry , ethylene glycol , polymer chemistry , cyclodextrin , hydrogen bond , organic chemistry , molecule
The temperature‐dependent phase transition behavior of acetylated polyrotaxanes (PRXs) consisting of acylated α‐cyclodextrins threaded onto a poly(ethylene glycol) chain in an aqueous solution is investigated. Acetyl (Ac), propionyl (Pr), and butyryl (Bu) group‐modified PRXs with different degrees of substitution are synthesized to elucidate the effect of the alkyl chain length of the acyl groups on temperature responsivity. Ac‐PRXs, Pr‐PRXs, and Bu‐PRXs are dissolved in water and exhibit temperature‐dependent transmittance changes accompanied by coacervate formation. However, the temperature responsivity of acylated PRXs is seen in limited degree of substitution range (≈10%). The maximum degree of substitution to show temperature responsivity of acylated PRXs decreases with increasing alkyl chain length of the acyl groups. Transmittance measurements of acylated PRXs in the presence of urea reveal that the alkyl chain length of the acyl groups determines the predominant force involved in the temperature‐induced phase transition. During the temperature‐induced phase transition of Pr‐PRXs and Bu‐PRXs, hydrophobic interactions are predominant; however, hydrogen bond formation may occur in Ac‐PRXs. These fundamental findings related to acylated PRXs will facilitate the application of PRXs as thermoresponsive supramolecular materials.