English Abstract

Synthesis of Cyclic Polymer : Polymer Topology-Transformation Utilizing Rotaxanefs Structural Characteristics

Toshikazu TAKATA
Hiroshima University, Higashihiroshima, Hiroshima, Japan
Nippon Gomu Kyokaishi,(2021),94(9),311-318 General Review in Japanese

Many polymer scientists have devoted to study on the synthesis and property of cyclic polymers which have no terminal end, being much different from most common polymers. In this review, we discuss mainly on the synthesis of cyclic polymers by utilizing the rotaxane’s structural characteristics, “the rotaxane method”. For it, the macromolecular rotaxane switch which can play an important role to control the polymer topology, i.e. linear or cyclic, has been synthesized to regulate the relative position of the components of macromolecular rotaxanes. Addition of [1]rotaxane moiety to polymer terminal gave [1]polyrotaxane of which crown ether wheel component was moved from one to another site by breaking the attractive interaction with the ammonium site to eventually afford “cyclic polymer". The solution property between linear and cyclic polymers obtained was compared to evaluate the effect of cyclic topology: cyclic polymer showed smaller hydrodynamic radii than the linear counterpart. Cyclic block copolymer having poly(ε -caprolactone)-b-(δ -hexanolactone)was also prepared via the living ring-opening polymerization followed by the terminal end-cap and the control of the attractive interaction. The cyclic topology was characterized by the difference in crystallinity and glass transition temperature in comparison with the linear one. Additional syntheses of cyclic polymers by different rotaxane methods will be discussed in the next chance.

Keywords: Cyclic Polymer, Rotaxane Switch, Polymer Topology, Topology Transformation, Linear-Cyclic Topology