3 research outputs found

    Effective Approach to Cyclic Polymer from Linear Polymer: Synthesis and Transformation of Macromolecular [1]Rotaxane

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    We report a convenient and scalable synthesis of cyclic poly­(ε-caprolactone) (PCL) from its linear counterpart based on the rotaxane protocol. Cyclic PCL was prepared by ring-opening polymerization of ε-caprolactone (ε-CL) initiated by a pseudo[2]­rotaxane initiator in the presence of diphenylphosphate (DPP) as a catalyst, followed by capping of the propagation end by using a bulky isocyanate to afford macromolecular [2]­rotaxane. The successive intramolecular cyclization to macromolecular [1]­rotaxane at the polymer terminus proceeded with good yield. The attractive interaction of the terminal ammonium/crown ether moiety was removed via N-acetylation. This enabled movement of the crown ether wheel along the axle PCL chain to the urethane region of the other terminus in solution state. Size-exclusion chromatography and 2D diffusion-ordered spectroscopy (DOSY) results demonstrated the formation of cyclic PCL from linear PCL, which is further supported by thermal property or crystallinity change before and after transformation

    Macromolecular [2]Rotaxanes: Effective Synthesis and Characterization

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    Macromolecular [2]­rotaxanes, which consist of a polymer chain threading into a wheel component, were synthesized in high yield and with high purity. The synthesis was achieved by the ring-opening polymerization (ROP) of δ-valerolactone (VL) using a hydroxyl-terminated pseudorotaxane as an initiator with diphenyl phosphate as a catalyst in dichloromethane at room temperature. The <sup>1</sup>H NMR, gel permeation chromatography (GPC), and MALDI-TOF-MS measurements of the resulting poly­(δ-valerolactone)­s clearly indicate the presence of the rotaxane structure with the polymer chain, confirming that the diphenyl phosphate-catalyzed ROP of VL proceeds without deslippage of the wheel component. The obtained macromolecular [2]­rotaxane was acetylated to afford a nonionic macromolecular [2]­rotaxane, in which only one wheel component is movable from one end to another along the polymer chain

    Thermoresponsive Shuttling of Rotaxane Containing Trichloroacetate Ion

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    A thermoresponsive rotaxane shuttling system was developed with a trichloroacetate counteranion of an ammonium/crown ether-type rotaxane. Chemoselective thermal decomposition of the ammonium trichloroacetate moiety on the rotaxane yielded the corresponding nonionic rotaxane accompanied by a positional change of the crown ether on the axle. The rotaxane skeleton facilitated effective dissociation of the acid, markedly lowering the thermal decomposition temperature
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