Thermally Responsive Poly(ethylene oxide)‐Based Polyrotaxanes Bearing Hydrogen‐Bonding Pillar[5]arene Rings **

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.