ACS Macro Letters最新文献

Injectable behavior is often observed in polymer-based hydrogels yet is rarely achieved in low-molecular-weight hydrogels (LMWHs), the realization of which may boost the development of new soft materials for biomedical applications. Here, we report on injectable self-healing and antidissolving LMWHs that are formed through a simple ionic cross-linking strategy, showing a fundamental application for the encapsulation of living cells. The LMWHs are formed by simply mixing Ca²⁺ with negatively charged supramolecular polymers. Surprisingly, the resultant hydrogels are capable of rapidly self-healing within seconds after damage, showing an unexpected injectable function. When the hydrogel is injected into an aqueous medium, continuous macroscopic hydrogel fibers can be produced. Interestingly, the hydrogel can remain intact in the aqueous medium, showing impressive antidissolving behavior which is less observed in other LMWHs. Furthermore, the hydrogel is demonstrated to be nontoxic and can be used as a cytocompatible scaffold for living cells. This work may open an avenue toward injectable and antidissolving LMWHs for the ever-expanding list of applications in biotherapy and bioprinting.

Flex-activated mechanophores capable of releasing small molecules utilize bond bending to facilitate their mechanochemical activation without compromising the overall macromolecular architecture, which have great potential in various applications. However, the development of such mechanophores remains underexplored. Here we report a novel flex-activated mechanophore based on the 1,4-Diels–Alder (DA) adduct of 9,10-diphenylanthracene (DPA) with acetylenedicarboxylate (ADC). Compression of the mechanophore-crosslinked polymer networks mechanochemically activates the weakly fluorescent DPA-ADC mechanophores to undergo a retro-DA reaction in accompany with the release of highly fluorescent DPA molecules (quantum yield close to unity), as confirmed by fluorescence spectroscopy and gas chromatography–mass spectrometry (GC-MS) analysis. As a new member of the small family of flex-activated mechanophores, this fluorogenic DPA-ADC mechanophore possesses promising applications in stress sensing and damage detection.

Host–guest interactions have been increasingly explored for use in the dynamic physical cross-linking of polymeric precursors to form hydrogel networks. However, the orientation of guest motifs is restricted upon macromolecule conjugation. The implications of such restriction on both the kinetics and thermodynamics of the resulting host–guest supramolecular cross-links are poorly understood. Herein, guest cross-linking motifs from controlled regioisomers are demonstrated to yield distinct material properties. Moreover, the underlying phenomena point to a further unexpected impact of modular guest topology on the molecular scale in both the affinity and dynamics of supramolecular complex formation.

Complex coacervate core micelles (C3Ms), formed through electrostatic interactions between oppositely charged block copolyelectrolytes, are effective delivery vehicles for hydrophilic biomacromolecules. This study investigates the impact of polymer architecture on the C3Ms structure by blending homopolyelectrolytes and diblock copolyelectrolytes as anionic counterparts for cationic diblock copolyelectrolytes. Our results show that the micellar structure, including core size, aggregation number, and corona characteristics, is precisely controlled by the fraction of homopolyelectrolytes. C3Ms formed by the AB + C system have larger core dimensions and aggregation numbers but lower corona brush densities compared to AB + AC systems. These findings highlight that the spatial constraints of polyelectrolytes play a crucial role in determining micellar structure, which can be further understood by balancing the free energies contributed by core block stretching and interfacial tension.

Recovering monomers from the depolymerization of thermosets presents a significant challenge, which becomes even more daunting if one sets the goal of doing it directly, i.e., without complex chemical separation steps. To this end, we have synthesized a new type of polycarbonate thermoset by first copolymerizing alkyl cyclic carbonates (ACCs) with small amounts of allyloxy cyclic carbonates (AoCCs), followed by cross-linking the resulting allyloxy polycarbonate with excess tetrathiol compounds under UV irradiation. These cross-linked polycarbonates demonstrate enhanced thermal and mechanical properties compared to their linear analogues, while maintaining the linear polymers’ capacity for ring-closing depolymerization. The depolymerization process enables the direct recovery of ACC and its dimer, bypassing complex chemical separation steps that are commonly employed in the recycling of conventional chemically recyclable thermosets. The yields range from 74.7% to 91.7% depending on the ratios of AoCC to ACC in the thermosets. Furthermore, the recovered compounds can be repolymerized with AoCCs leading to polycarbonate of the same quality to the initially synthesized one.