Robust Vanillin-Derived Poly(thioether imidazoles) as Both a Latent Curing and Toughening Agent for One-Component Epoxy Resins

Abstract

One-component epoxy resins based on latent curing agents have garnered research attention owing to their outstanding storage stability and excellent processability, while their development considerably depends on the design and preparation of sustainable latent curing agents. Herein, taking structural advantage of lignin-derived vanillin, a biobased polymerizable aromatic imidazole monomer with α,ω-diene functionality was designed and prepared, which was applicable in subsequent thiol–ene polymerization, yielding a series of robust poly(thioether imidazoles) with excellent tunability of the structure and properties. The findings indicated that the precursors comprising poly(thioether imidazole) and commercially available epoxy resins could keep their fluidity at 25 °C for over 90 days and rapidly cured into resins under elevated temperature, demonstrating that the poly(thioether imidazole) can serve as both a latent curing and toughening agent for one-component epoxy resins because of homopolymerization initiated by imidazole groups and the introduction of an aliphatic chain in the as-prepared poly(thioether imidazole) matrix.

Resveratrol-Derived Liquid Crystal Epoxy Resin with Low-Dielectric Properties and Excellent Mechanical Strength and Toughness

“…This test result demonstrated the excellent mechanical strength and toughness of AE-Res/BPDGE, which was higher than most biobased curing agent-cured epoxy resins (Table S4). ,− This phenomenon is mainly attributed to AE-Res having more benzene structures and BPDGE having a rigid biphenyl structure. Meanwhile, a large number of flexible ether bonds are produced by the active esters after curing the epoxy.…”

Robustly Curing Epoxy Novolacs by Linear and Cyclic Siloxane-Functionalized Eugenol: Impact of Topologies of Cross-Linkers on Properties of Thermosets

“…They usually bear more than two reactive hydrogens, at least one cyclic anhydride group, or certain catalytic moieties that can lead to cross-linking of epoxy resins as bisphenol A diglycidylether (DGEBA). Moreover, certain biobased curing agents could bring some unusual properties such as intrinsic flame retardancy, − latent curing, , repressibility, and high toughness to the resulting epoxy thermosets. Especially, eugenol is a natural product that is the main component (>80%) of clove oil and is of low toxicity with stable accessibility.…”

High-Performance One-Component Epoxy Adhesive Based on the Synergistic Effect of Lignin-Derived Triaryl-Imidazole and Phytic Acid

“…7−9 The fundamental concept is to impede the electron-rich curing agent at either the phase 10−13 or molecular level, 14−18 resulting in the latent curing agents. Imidazole derivatives have been extensively researched as intrinsic latent curing agents, and various modification strategies have been devised to incorporate hindered groups, including nucleophilic substitution, 7 ionic complexation, 14 metal coordination, 19 and hydrogen bonding. 20 The increasing focus on environmental issues in recent years has presented new challenges to epoxy resins, and the main challenge arises from the raw materials, as the majority of epoxy resins are derived from nonrenewable petroleum chemicals.…”

“…The problem often leads to structural defects − in the adhesion layer and compromises bonding quality. To address the aforementioned limitations, one-component epoxy resins have been formulated. − The fundamental concept is to impede the electron-rich curing agent at either the phase − or molecular level, − resulting in the latent curing agents. Imidazole derivatives have been extensively researched as intrinsic latent curing agents, and various modification strategies have been devised to incorporate hindered groups, including nucleophilic substitution, ionic complexation, metal coordination, and hydrogen bonding …”

“…The increasing focus on environmental issues in recent years has presented new challenges to epoxy resins, and the main challenge arises from the raw materials, as the majority of epoxy resins are derived from nonrenewable petroleum chemicals. A potential resolution for this predicament is replacing the nonrenewable petroleum feedstock with abundant and renewable biomass. − To date, the majority of research on biobased epoxy resins have put their focus on biobased prepolymers. − Conversely, there has been comparatively less emphasis on biobased curing agents, particularly the biobased latent curing agents. ,− To the best of our knowledge, the latent curing agent with the aromatic skeleton and 100% biobased carbon content has not yet been documented.…”