Spiroborate-Linked Ionic Covalent Adaptable Networks with Rapid Reprocessability and Closed-Loop Recyclability

Abstract

Covalent adaptable networks (CANs) represent a novel class of polymeric materials crosslinked by dynamic covalent bonds. Since their first discovery, CANs have attracted great attention due to their high mechanical strength and stability like conventional thermosets under service conditions and easy reprocessability like thermoplastics under certain external stimuli. Here, we report the first example of ionic covalent adaptable networks (ICANs), a type of crosslinked ionomers, consisting of negatively charged backbone structures. More specifically, two ICANs with different backbone compositions were prepared through spiroborate chemistry.Given the dynamic nature of the spiroborate linkages, the resulting ionomer thermosets display rapid reprocessability and closedloop recyclability under mild conditions. The materials mechanically broken into smaller pieces can be reprocessed into coherent solids at 120 °C within only 1 min with nearly 100% recovery of the mechanical properties. Upon treating the ICANs with dilute hydrochloric acid at room temperature, the valuable monomers can be easily chemically recycled in almost quantitative yield. This work demonstrates the great potential of spiroborate bonds as a novel dynamic ionic linkage for development of new reprocessable and recyclable ionomer thermosets.

A UV-responsive mechanically robust insulating polymer that achieves intrinsic self-healing of electrical tree damage based on reversible anthracene photodimerization

“…This characterization showed that the tensile strength of HCIS-EP was comparable to that of conventional EP, and the strength remained high after five cycles of decrosslinking and crosslinking. Compared with the self-healing materials reported in other studies, 36–45 ISEP-RAP in this study had major advantages in terms of excitation conditions, mechanical properties, and healing (Fig. 8(b)).…”

Direct and Catalyst-Free Ester Metathesis Reaction for Covalent Adaptable Networks

“…When associative CANs are triggered, the cleavage and bonding occur simultaneously, and the cross-linking density remains constant, which are also coined “vitrimers” by Leibler and co-workers because of the silica-like rheological behavior . A variety of CANs have been reported via the introduction of DCBs, − such as dynamic imine, , disulfide (selenide), − Diels–Alder cycloaddition, − transesterification, ,− thioester, silyl ether/siloxane, , boronic ester, − reversible isocyanate chemistry, − transamination, , transamidation, , transalkylation, nucleophilic aromatic substitution, and reversible conjugate addition. − …”

3D Printing of continuous fiber composites using two-stage UV curable resin

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