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.

Supramolecular polymers based on host−guest molecular recognition have emerged as promising platforms for the development of smart materials. However, the studies on them are primarily conducted in solution and/or in the gel state. In contrast, little is known about dynamic properties and applications of supramolecular polymers in bulk. Herein, we present a selfcross-linking supramolecular polymer network (SPN) as a model system to understand the bulk properties controlled by noncovalent interactions. Specifically, the SPN monomer is composed of two benzo-21-crown-7 (B21C7) host units and two dialkylammonium salt guest moieties on a four-arm core, wherein complementary host−guest complexation drives the formation of the SPN with [2]pseudorotaxane linkages between B21C7 and ammonium motifs. The dynamic and reversible behaviors of the linkages are evaluated by measurement of viscoelasticity. The results indicate that the host−guest molecular recognition becomes highly dynamic at elevated temperature. Moreover, the relatively high activation energy of the SPN manifests itself as a new type of thermoplastic material with network topology freezing glass transition. Finally, we demonstrate how these findings provide insights into the malleability and processability of the SPN by simple demos. The fundamental understanding gained from the research on this SPN in bulk will facilitate the advancement and application of supramolecular materials.

Nature has engineered delicate synergistic covalent and supramolecular polymers (CSPs) to achieve advanced life functions,s uch as the thin filaments that assist in muscle contraction. Constructing artificial synergistic CSP materials with bioinspired mechanically adaptive features,h owever, represents ac hallenging goal. Here,w er eport an artificial CSP system to illustrate the integration of ac ovalent polymer (CP) and as upramolecular polymer (SP) in as ynergistic fashion, along with the emergence of notable mechanical and dynamic properties which are unattainable when the two polymers are formed individually.T he synergistic effect relies on the peculiar network structures of the SP and CPs,w hich endowt he resultant CSPs with overall improved mechanical performance in terms of the stiffness,s trength, stretchability, toughness,and elastic recovery.Moreover,the dynamic properties of the SP,i ncluding self-healing,s timuli-responsiveness, and reprocessing,are also retained in the CSPs,thus leading to their application as programmable and tunable materials.

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A novel, clean biological transformation reaction by immobilized Rhodobacter sphaeroides has been developed for the synthesis of zinc sulfide (ZnS) nanoparticles with an average diameter of 8 nm. The nanoparticles were examined by X-ray diffraction, transmission electron microscopy, energy dispersive analyses of X-rays, UV-vis optical absorption and photoluminescence spectra. The average diameter of ZnS nanoparticles varied according to the culture time.