New Prospects Arising from Dynamically Crosslinked Polymers: Reprogramming Their Properties.

Dynamically crosslinked polymers (DCPs) have gained significant attention owing to their applications in fabricating (re)processable, recyclable, and self-healable thermosets, which hold great promise in addressing ecological issues, such as plastic pollution and resource scarcity. However, the current research predominantly focuses on redefining and/or manipulating their geometries while replicating their bulk properties. Given the inherent design flexibility of dynamic covalent networks, DCPs also exhibit a remarkable potential for various novel applications through postsynthesis reprogramming their properties. In this review, the recent advancements in strategies that enable DCPs to transform their bulk properties after synthesis are presented. The underlying mechanisms and associated material properties are overviewed mainly through three distinct strategies, namely latent catalysts, material-growth, and topology isomerizable networks. Furthermore, the mutual relationship and impact of these strategies when integrated within one material system are also discussed. Finally, the application prospects and relevant issues necessitating further investigation, along with the potential solutions are analyzed.

Fast Damage-Healing of Rigid Photocuring 3D Printing Materials Capable of Directly Recycling in 3D Printing.

Rigid 3D printing materials often get defects such as cavities, voids, holes, or gaps when suffering from impact forces. Fast self-healing of these damages without bulk temperature increase is always desired. Besides, the recycling of dynamically cross-linked polymers was usually focused on solvent- or heat-assisted strategies such as compression molding and dissolution-casting, which restricts the geometrical diversity of recycled materials and may cause environmental issues. Here we report a rigid photocuring 3D printing material that can heal its cave-like damage quickly under UV light based on the dynamic urea bond. Besides, after grounding the printed objects into powders and directly refilling them into new printing resin, the re-3D printed objects show similar mechanical properties to the original materials without any post-treatment.

Stabilization of the hindered urea bond through de-tert-butylation.

We report the discovery of an acid-assisted de-tert-butylation reaction that can instantly "turn off" the dynamicity of hindered urea bonds (HUBs) and thus broaden their applications. The reaction is demonstrated to be widely applicable to different hindered urea substrates, leading to improved chemical stabilities and mechanical properties of HUB-containing materials.