English Abstract

Synthesis of Cyclic Polymer: Polymer Topology-Transformation
Utilizing Rotaxane's Structural Characteristics (II)

Toshikazu TAKATA
Hiroshima University, Higashihiroshima, Hiroshima, Japan
Nippon Gomu Kyokaishi,(2022),95(3),96-102 General Review in Japanese

Continuing to the previous report, we discuss on the synthesis of cyclic polymers based on the grotaxane protocolh. Although the synthesis of pure cyclic polymer is a tough challenge, recent advances on this subject have gradually overcome the problems associated with it: we have succeeded in synthesizing pure cyclic polymers through the ring-expansion of the small cyclic structure to cyclic polymer using the concept of glinear to cyclic polymer topological transformationhcaused by the high structural flexibility or component mobility of rotaxane. In the light of a limited number of cyclic vinyl polymers, cyclic poly(methyl acrylate) was prepared by transforming [1]polyrotaxane-type linear poly(methyl acrylate) to cyclic poly(methyl acrylate) by moving the wheel component of [1]polyrotaxane from one terminal to other terminal by the action of macromolecular rotaxane switch. High-yielding synthesis of cyclic polymer was achieved by the spontaneous dimerization to Janus-shaped rotaxane derived from an ammonium moiety- containing crown ether, of which axle components have hydroxy terminals. The introduction of two polymer chains to the two hydroxy terminals for the synthesis of linear polymer was followed by the movement of the wheel components from the center to the axle terminal by using the rotaxane switch, to eventually yield cyclic polymer. The process of the cyclic polymer formation requires no diluted concentration condition, and therefore 7.3 g of pure cyclic polymer was obtained from a 50 mL reaction flask, suggesting that the present protocol provides the reliable useful synthetic method of cyclic polymer.

Keywords: Cyclic Polymer, Rotaxane Switch, Polymer Topology, Topological Change, Linear-Cyclic Polymer Transformation, Rotaxane Protocol