Thermally Responsive Poly(ethylene oxide)‐Based Polyrotaxanes Bearing Hydrogen‐Bonding Pillar[5]arene Rings**
Kenichi Kato, Katsuto Onishi, Koki Maeda, Masafumi Yagyu, Shixin Fa, Takahiro Ichikawa, Motohiro Mizuno, Takahiro Kakuta, Tada‐aki Yamagishi, Tomoki Ogoshi
Abstract
Poly(ethylene oxide)s (PEOs) are useful polymers with good water solubility, biological compatibility, and commercial availability. PEOs with various end groups were threaded into pillar[5]arene rings in a mixture of water and methanol to afford pseudopolyrotaxanes. Corresponding polyrotaxanes were also constructed by capping COOH-terminated pseudopolyrotaxanes with bulky amines, in which multiple hydrogen bonds involving the pillar[5]arene OH groups were critically important to prevent dethreading. The number of threaded ring components could be rationally controlled in these materials, providing a simple and versatile method to tune the mechanical and thermal properties. Specifically, a polyrotaxane with a high-molecular-weight axle became elastic upon heating above the melting point of PEOs and exhibited temperature-dependent shape memory property because of the topological confinement and crosslinked hydrogen bonds.