Improvement of Polymer Mechanical Behaviors by Introducing [2]Rotaxane Units with Intra- and Intermolecular Hydrogen Bonds

Rotaxanes have demonstrated great potential in the development of smart materials owing to their attractive dynamic and movable properties. However, it remains a significant challenge to construct polymers with outstanding mechanical performance by the introduction of rotaxane units. Here, we synthesized several pillar[5]arene-based [2]rotaxanes by condensation reaction of 1-naphthyl isocyanate and alkyl diamines and introduced them into covalent polymers through ring-opening metathesis polymerization. The rigid and bulky pillar[5]arene units, sliding motions of rotaxane moieties, and intra- and intermolecular hydrogen bonds between urea groups endow the polymers with excellent mechanical properties (PR4: Young's modulus = 360.1 ± 32.1 MPa, yield stress = 14.2 ± 0.1 MPa, stress at break = 14.8 ± 0.6 MPa, and toughness = 67.8 ± 2.0 MJ/m3). Moreover, the mechanical properties of PR4 could be weakened and strengthened by the introduction of Ac– and Cl–, respectively, showing their abundant regulable features. These findings provide novel insights into the preparation of advanced supramolecular materials with enhanced mechanical properties.