Scaffolded Thermally Remendable Hybrid Polymer Networks

Abstract

Step‐growth Diels–Alder (DA) networks using furan and maleimide groups are particularly useful in forming thermally remendable crosslinked polymers, due to the dramatic shift in equilibrium over a relatively low temperature range as compared with other diene‐dienophile pairs. However, the efficient healing observed in these materials at high temperature is directly tied to their ability to depolymerize and flow, and thermal treatment often results in deformation of the original shape. To overcome this limitation, a hybrid network material is developed, which consists of orthogonal Diels–Alder and polyurethane networks. Both step‐growth networks form simultaneously at elevated temperature without the presence of a catalyst. At high temperatures, the Diels–Alder network depolymerizes and flows into fractures through capillary action, while the polyurethane serves as a scaffold to maintain the overall shape of the sample. The DA network then repolymerizes at lower temperatures, creating a crosslinked, scar‐like “patch” throughout the crack. This healing process is repeatable without concern of monomer depletion. During heating through the glass transition, a shape memory “assist” is observed, which reverses some of the localized damage by bringing broken edges closer together. Samples are repeatedly damaged and then healed through temperature cycling, as evidenced through tensile fracture tests and electrochemical conductivity tests.

Transiently malleable multi-healable hydrogel nanocomposites based on responsive boronic acid copolymers

“…[5][6][7][8] The latter approach is particularly interesting and challenging in that suitable chemistries must be adopted that do not compromise the end-functionality of the designed material. Notable approaches of this method include the construction of healable polymer networks based on the exploitation of hydrogen bonds, [9][10][11] π-π stacking type of interactions, 12,13 host-guest recognition events, [14][15][16][17] electrostatic interactions, 18,19 metal coordination, [20][21][22] acylhydrazones, 23,24 reversible (hetero) Diels-Alder reaction motifs [25][26][27][28] and disulfide bonds. [29][30][31] Indeed, all these approaches have their own merits, however, the healing process is not always ex vi termini perfect as autonomous/automatic healing must be accompanied by gravitational force or mechanical/manual rejoining of the damaged material.…”

The effect of electron density in furan pendant group on thermal-reversible Diels–Alder reaction based self-healing properties of polymethacrylate derivatives

“…Applications of the DA reaction in self-healing materials have been widely studied due to the aforementioned advantages. [24][25][26][27][28][29] However, many studies were focused on synthesizing new selfhealable materials based on the DA reaction rather than investigating the inuence of the reactivity of the DA reaction on self-healing efficiency. Therefore, herein, to study the inuence of the reactivity of the DA reaction on self-healing efficiency, self-healable polymethacrylates having furan pendant groups with different electron densities were synthesized and characterized.…”

Ambient temperature induced Diels–Alder crosslinked networks based on controlled methacrylate copolymers for enhanced thermoreversibility and self-healability

“…Most of DA-crosslinked networks were fabricated through step-growth polyaddition or coupling reaction of polymaleimides and polyfurans. [48][49][50][51][52][53][54][55][56][57] Of our interests are thermo-labile networks based on reactive methacrylate copolymers. The nature of the polymethacrylate backbones of carbon-carbon single bonds, the high molecular weight of polymeric chains, and the facile copolymerization with so monomers allow for tuning the balance of rigidity and exibility of methacrylate networks.…”