Catalyst-Free Metathesis of Cyclic Acetals and Spirocyclic Acetal Covalent Adaptable Networks

Abstract

Due to the exchangeability of dynamic covalent bonds in the covalent adaptable networks (CANs) at elevated temperature, they possess recyclability while still maintaining many of the superior properties of thermosets. The exploration of dynamic covalent chemistry is of great significance to the expansion of CANs library and hence the sustainable development of thermosets. In this work, we discovered that, in absence of catalyst, the direct metathesis of the cyclic acetals proceeds while the acyclic acetals cannot. The metathesis kinetics of the cyclic acetals were fully revealed with model compounds. For the CANs demonstration, a series of cross-linked spirocyclic acetal polymers with excellent reprocessability, high thermal stability, and high refractivity were prepared via thiol–ene click polymerization. We envisage that the uncovering of the catalyst-free metathesis of cyclic acetals will enrich the dynamic chemistry of acetals and greatly promote the development of acetal-based CANs and their potential applications in optical devices.

Based on transalkylation reaction the rearrangeable conventional sulfur network facile design for vulcanized diolefin elastomers

“…Conventionally, the liquid to glass transition of polymer liquid deviates from Arrhenius behavior. However, the temperature dependence of relaxation time conforms to Arrhenius relationship and a linear relationship can be observed, which is the characteristic for vitrimer materials 38–42 . The activation energy for exchange reaction is 87 kJ/mol.…”

“…However, the temperature dependence of relaxation time conforms to Arrhenius relationship and a linear relationship can be observed, which is the characteristic for vitrimer materials. [38][39][40][41][42] The activation energy for exchange reaction is 87 kJ/mol. The temperature dependence of thermal expansion, which indicates the topology freezing transition above the classical glass transition temperature, is obtained in Figure 3d.…”

Fully Biobased Vitrimers: Future Direction toward Sustainable Cross‐Linked Polymers

“…[162,163] Especially, acetal metathesis has been proven to occur in cross-linked spiro acetal polymers under cat-alyst free conditions. [164] Ma and coworkers implemented this strategy to prepare partially biobased degradable epoxy resins based on vanillin derived diacetal structures. [165] In this study, bisphenol monomers, exhibiting spiroacetal linkages, were synthesized by reaction of 2 equivalents of vanillin with pentaerythritol or with erythritol.…”

Thermal Healing of Copolyacrylate Elastomer Based on Catalyst‐Free Transketalization

“…Therefore, the incorporation of acetal/ketal structure does not cause a decrease in the initial decomposition temperature of the polymer. [ 39–41 ] Similar to the polymer including B─O bond (518.6 kJ mol −1 ), [ 42 ] the copolyacrylate may show high thermal stability as a result of the incorporation of acetal/ketal.…”