Crystallinity and Cooperative Motions of Cyclic Molecules in Partially Threaded Solid-State Polyrotaxanes

Abstract

We investigated the structure, thermal properties, and dynamics of polyrotaxane (PR), composed of poly(ethylene glycol) (PEG) and α-cyclodextrins (CDs), and PR derivatives comprising hydroxypropylated CDs, that is, hydroxypropylated PRs (HyPRs), in the solid state by using wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and viscoelastic spectroscopy. It was observed that HyPRs with high chemical modification ratios show a WLF-type viscoelastic relaxation that can be ascribed to the cooperative segmental motion of several CD molecules, whereas HyPRs with a lower modification ratio and PR with a highly ordered packing structure of CDs do not exhibit any mechanical relaxation mode. A comparison between the relaxation temperatures of HyPRs with different modification and inclusion ratios suggested that the hydrogen bond between CDs primarily dominates the viscoelastic properties of solid-state PR. Our experimental results indicate a close relationship between the crystallinity and fluctuation of cyclic molecules in solid-state PR, which is the first evidence of the dynamic softening of the glassy state formed by assembled cyclic molecules in solid-state PR.

Synthesis and Characterization of Polyurethanes Crosslinked by Polyrotaxanes of Two Filling Ratios of ^|^alpha;-Cyclodextrin and with Two Modification Ratios of Polyurethane Chain

“…Since then, a lot of PRXs have been reported [22][23][24][25][26][27][28] . An elegant sliding network gel based on a PRX consisting of α-CyD and a PEG with long chain lengths was reported by Ito, et al and they described their physical properties in detail [29][30][31][32][33][34] . Hadziioannou, et al also reported similar sliding gels [35][36][37] .…”

Implementation of the Pulley Effect of Polyrotaxane in Transparent Bulk Polymer for Simultaneous Strengthening and Toughening

“…the movement or rotation of the α-CD rings is rarely adopted for improving mechanical properties of bulk polymers, probably because the easy aggregation of α-CDs via hydrogen bonding between the abundant hydroxyl groups greatly reduces the mobility. [2,16] The situation has changed recently. A few elastomers crosslinked by modified polyrotaxane demonstrated that the pulley effect can also be realized in polymer networks in the absence of water.…”

“…Nevertheless, the interesting pulley effect generated by the movement or rotation of the α‐CD rings is rarely adopted for improving mechanical properties of bulk polymers, probably because the easy aggregation of α‐CDs via hydrogen bonding between the abundant hydroxyl groups greatly reduces the mobility. [ 2,16 ]…”

Versatile synthesis of end-reactive polyrotaxanes applicable to fabrication of supramolecular biomaterials

“…This free mobility of threading CDs in PRXs is attractive for the development of functional supramolecular materials [4–6]. In PRX applications, chemical modification of the threading CDs is important to reduce intermolecular interactions of the PRXs, impart solubility in organic solvents and water, and introduce functional molecules [7–9]. In this regard, various methods of introducing functional groups at the threading CD moieties of PRXs are used.…”