Rapid Stress Relaxation, Multistimuli-Responsive Elastomer Based on Dual-Dynamic Covalent Bonds and Aniline Trimer

Abstract

Covalent adaptable networks (CANs) are an emerging kind of smart materials in which cross-links are reversible upon some stimuli and then provide malleability and a stimuliresponsive ability to the materials. There is a trend to endow CANs with multistimuli-responsive capabilities and rapid stress relaxation to pursue more advanced applications. To integrate these two features into one material, here, dual-dynamic covalent bonds (imines and boronic esters) and aniline trimer (ACAT) were incorporated into the styrene butadiene elastomer as dynamic cross-links. The obtained CANs were demonstrated with rapid stress relaxation and a relatively low activation energy of 36 ± 1 kJ mol −1 , resulting from the synergistic effect of dual-dynamic covalent bonds to rearrange the network at a faster rate than for either imines or boronic esters. Because of the dynamic nature of imines or boronic esters, the elastomer can be recycled upon heat. Moreover, the appearance and configuration of the elastomer could also be manipulated by pH and light because of the inclusion of ACAT. All in all, the coupled multistimuli-responsive behavior and rapid stress relaxation in one single elastomer would potentially be applicable for sensors and actuators with good recyclability.

Biobased catalyst-free covalent adaptable networks based on CF3-activated synergistic aza-Michael exchange and transesterification

“…51 Du Prez et al also studied This journal is © The Royal Society of Chemistry 2022 dynamic thiol-yne cross-linking as a new platform for the exchange of thioacetal linkages and demonstrated that associative and dissociative mechanisms occurred concomitantly. 52 Following the development of these dual systems previously reported, 51,53,54 BAE-F-OH was synthesized to produce a network in which aza-Michael exchange and trans-esterication can concomitantly occur. Both exchange reactions were activated by the presence of the CF 3 group in the alpha and beta positions of the ester function and of the nitrogen atom respectively.…”

Sustainable Polyurethane Networks with High Self‐Healing and Mechanical Properties Based on Dual Dynamic Covalent Bonds

“…The proposed mechanism of synergistic effect in vitrimer network is consistent with reported works. [ 31,67,68 ] $$$$\begin{equation} \ln \tau = \ln {\tau _0} + \frac{{{E_a}}}{{RT}} \end{equation}$$$$…”

“…Linear the HHMB-4-0 shows the fastest stress relaxation; the HHMB-4-20 with dual dynamic bonds quickly relaxes than the HHMB-0-20 with single dynamic bonds. [67,68] The lowest E a of the HHMB-4-20 with disulfide bonds and boronic ester bonds indicates synergistic effects of disulfide and dioxaborolane metathesis leading to a faster exchange reaction at low temperatures. When dynamic covalent bonds in a network are exchanged at elevated temperatures, mobility of the network can be improved.…”

“…The proposed mechanism of synergistic effect in vitrimer network is consistent with reported works. [31,67,68] ln…”

Recyclable photoluminescent elastomer incorporating carboxyl‐functionalized fluorescent powder via dynamic covalent cross‐linking

“…By using the dynamic exchange property of imine groups in polymers, they endow them with reprocessability, self‐healing property and degradability. Liu et al [ 32 ] first use the thiol‐ene “click” reaction between SBR and thiodiglycol to hydroxylate double bonds in SBR. Then they use 4‐formylbenzoboronic acid (FBA) and aniline trimer (ACAT) as cross‐linking agents to introduce borate ester bonds and imine bonds into the same cross‐linking network.…”