Mechanically Interlocked Vitrimers

Abstract

Mechanically interlocked networks (MINs) have emerged as an encouraging platform for the development of mechanically robust yet adaptive materials. However, the difficulty in reversibly breaking the mechanical bonds poses a real challenge to MINs as customizable and sustainable materials. Herein, we couple the vitrimer chemistry with mechanically interlocked structures to generate a new class of MINsreferred to as mechanically interlocked vitrimers (MIVs)to address the challenge. Specifically, we have prepared the acetoacetatedecorated [2]rotaxane that undergoes catalyst-free condensation reaction with two commercially available multiamine monomers to furnish MIVs. Compared with the control whose wheels are nonslidable under applied force, our MIVs with slidable mechanically interlocked motifs showcase enhanced mechanical performance including Young's modulus (18.5 ± 0.9 vs 1.0 ± 0.1 MPa), toughness (3.7 ± 0.1 vs 0.9 ± 0.1 MJ/m 3 ), and damping capacity (98% vs 72%). The structural basis behind unique property profiles is demonstrated to be the force-induced host−guest dissociation and consequential intramolecular sliding of the wheels along the axles. The peculiar behaviors represent a consecutive energy dissipation mechanism, which provides a complement to other pathways that mainly depend on the breaking of sacrificial bonds. Moreover, by virtue of the vitrimer chemistry of vinylogous urethanes, we impart reprocessability and chemical recyclability to the MINs, thereby empowering the reconfiguration of the networks without breaking of the mechanical bonds. Finally, it is disclosed that the intramolecular motions of [2]rotaxanes could accelerate the dynamic exchange of the vinylogous urethane bonds via loosening the network, suggestive of a synergistic effect between the dual dynamic entities.

Second Natural Rubber with Self-Reinforcing Effect Based on Strain-Induced Crystallization

“…As shown in Figure 5d, EEUG-17.4%-DTSA-2 became more whitish when it was stretched to a strain of 1000%, suggesting the formation of crystals at high strain. 34 The energy dissipation of EEUG-17.4%-DTSA-2 at different strains was characterized by using cyclic tensile tests with an increasing strain but no delay time 45 SBR/PEI interlocked networks, 28 PU (hydrogen bonds), 46 PB dual network, 25 ENR/chitosan, 47 ENR/cellulose, 48 MIVs (mechanically interlocked vitrimers), 49 and SBR-M.HPDI.Upy dynamic liquid crystal networks. 50 (Figure 5e), and the hysteresis area represents the dissipated energy during each cycle.…”

“…(a) Stress−strain curve and (b) cyclic tensile−strain curves of EEUG-14.5%-DTSA-2, EEUG-14.5%-DTSA-3, and EEUG-17.4%-DTSA-2. (c) Comparison of mechanical properties with other recyclable elastomers: PDMS-Zn,45 SBR/PEI interlocked networks,28 PU (hydrogen bonds),46 PB dual network,25 ENR/chitosan,47 ENR/cellulose,48 MIVs (mechanically interlocked vitrimers),49 and SBR-M.HPDI.Upy dynamic liquid crystal networks 50. (d) Digital images showing the whitening process of the EEUG-17.4%-DTSA-2 at strain from 0 to 1000%.…”

Mechanically interlocked polymers based on rotaxanes

“…Although the MINs have shown distinct advantages when constructing materials with excellent mechanical properties, achieving the reprocessing and chemically recyclable performance of these materials remains a challenge. By combining the vitrimer chemistry with mechanically interlocked structures, a new class of MINs, known as mechanically interlocked vitrimers (MIVs), 240 addresses the challenge of constructing customizable and sustainable materials (Fig. 11b).…”

Dynamic Covalent Bond Cross‐Linked Luminescent Silicone Elastomer with Self‐Healing and Recyclable Properties

“…Dynamic covalent bonding with a dynamic equilibrium of breakage and reconfiguration allows for rapid network rearrangement under different environmental stimuli so that the elastomers can be recycled. [38,44,52] Two processes, solution processing and hot pressing, were used to reprocess elastomers P1-3 and P2-3 (Figure 5a,b). To study the recycle property, the samples were cut into pieces, then dissolved in CHCl 3 .…”