Synthesis and characterization of a mechanically linked transformable polymer

A shape-transformable polymer in which the wheel component can move freely along the axle chain was synthesized and characterized. Rotaxane-linked linear poly(delta-valerolactone) was synthesized in one pot via ring-opening polymerization initiated by a sec-ammonium/crown ether-type pseudo[2]rotaxane that possessed two initiating hydroxyl groups on both the axle and wheel components; this was followed by an end-capping reaction with a bulky isocyanate. Acetylation of the obtained polymer to remove the interaction between the sec-ammonium axle and the crown ether wheel afforded the transformable polymer. The movement of the wheel component bearing a polymer chain was confirmed by weakening the interaction between the axle and the wheel in the rotaxane-linked linear polymer that did not possess a bulky end-cap group. The result clearly supported the mobility of the wheel component bearing a graft chain from one end of the polymeric axle chain to the other end.