Coded Interlocked Covalent Adaptable Networks Enabled by Parallel Connections of Cation−π Interactions and Aromatic Disulfide Bonds in Epoxy

Abstract

Covalent adaptable networks (CANs) that are cross-linked by reversible dynamic bonds have been widely investigated, aiming at making the permanently cross-linked thermosets degradable and recyclable from the awareness of economic and environmental aspects. However, it is still a great challenge to make rigid thermosets like epoxy degradable upon programmed or coded stimuli, which will highly improve the combination of the degradable properties and stability. Herein, coded interlocked covalent adaptable networks (ICANs) in rigid epoxy were cross-linked by two distinct dynamic bonds of cation−π interactions and aromatic disulfide bonds in parallel connection, which exhibited high performance and coded or programmed degradation behavior. The coded ICANs were prepared by one-pot reactions from epoxy monomers and two curing agents that contained different dynamic bonds of cation−π interactions and aromatic disulfide bonds. The coded ICANs exhibited excellent mechanical properties and outstanding solvent resistance compared to the reference CANs or noncovalent adaptable networks (NCANs) relying on single dynamic bonds. Moreover, the coded ICANs exhibited unique programmed degradation behaviors, which could only be degraded after sequential exposure to two different chemical stimuli. Unlike the normal ICANs that could be degraded by two stimuli in any sequence, the coded ICANs were insoluble when the two stimuli were applied in the wrong sequence. The coded ICANs of epoxy provided a way to construct degradable CANs with more stable networks, while this concept and function might be applicable in other skeletons, leading to other types of highly coded ICANs with high performance and controlled degradation properties.

Reprocessable Silyl Ether-Based Dynamic Covalent Poly(dimethylsiloxane) Networks with Superb Thermal Stability and Creep Resistance

“…Among these materials, polydimethylsiloxane (PDMS) elastomers, with their distinctive molecular structure, play a strategically significant role in various fields including national defense and military industry, electronics, and aerospace industry. − However, due to their permanent cross-linked structure, thermoset PDMS elastomers are nonmelting and insoluble. This renders them difficult to reprocess and recycle, leading to considerable resource wastage and environmental pollution. − Consequently, there is an urgent need to develop a kind of PDMS elastomer material that not only retains the superior properties of thermosetting materials but also is capable of being reprocessed multiple times.…”

Oligosiloxane-Based Epoxy Vitrimers: Adaptable Thermosetting Networks with Dual Dynamic Bonds

“…Although there are a few examples of networks with multiple dynamic bonds in a single network, many of these systems consist of a mix of covalent and noncovalent bonds rather than purely covalent bonds . In contrast, dual dynamic covalent bond networks are less prevalent but may offer improved properties.…”