Polyurethane Elastomers Strengthened by Pseudo[1]rotaxanes Based on Pillararenes.

As a unique property of the interlocked structures, rotaxane allows for intramolecular motions between its wheel and axle components. Introduction of rotaxanes into polymers can endow them with distinctive macroscopic features and outstanding mechanical properties. Here, we prepare a copillar[5]arene with a hydroxyl and an amino-group on each end, which can spontaneously form a pseudo[1]rotaxane through intramolecular hydrogen bonds. This pseudo[1]rotaxane possesses a releasable extra alkyl chain, which is then incorporated into a linear polyurethane by reacting with a diisocyanate to prepare polyurethane elastomers with spring-like structures. The results of stress-strain test and dynamic mechanical analysis all indicate that sliding motions of the axle part on the pseudo[1]rotaxane in the polymer skeleton can greatly dissipate energy, which endows the elastomers with higher toughness and better fatigue resistance. Moreover, the addition of moderate amount of cuprous bromide to form cuprous-thioether coordination in the polymers can further improve the mechanical properties.