Chemically debondable, high-strength and tough adhesives from sulfur-modified epoxy networks

Abstract

Epoxy resins are among the best performing adhesives. Recovering the adhesively jointed parts for repetitive use demands innovative bonding strategies to afford facile debonding while not sacrificing the adhesion performance....

Bio-Based Reprocessable and Degradable Epoxy Resins via Inverse Vulcanization

“…4 Increasing concerns over the shortage of fossils and post-usage impact of these hard-to-degrade materials have stimulated innovations to utilize bio-derived raw materials for making performance competitive counterparts while also endowing recyclability and degradability. 5,6 Nearly all available biomasses, either in the form of macromolecules (lignin, tannic acid, and hemicellulose) or in the form of chemicals (soybean oil, terpene, rosin acids, etc. ), have been explored for the preparation of epoxy resins.…”

“…As one of the most important thermosets, epoxy resins exhibit superior thermal and mechanical properties and are irreplaceable in a broad spectrum of applications ranging from electronic packaging to high-performance composites. − Over 70% of epoxy resins are highly cross-linked networks from petroleum-based diglycidyl ether of bisphenol-A (DGEBA) . Increasing concerns over the shortage of fossils and post-usage impact of these hard-to-degrade materials have stimulated innovations to utilize bio-derived raw materials for making performance competitive counterparts while also endowing recyclability and degradability. , Nearly all available biomasses, either in the form of macromolecules (lignin, tannic acid, and hemicellulose) or in the form of chemicals (soybean oil, terpene, rosin acids, etc. ), have been explored for the preparation of epoxy resins. − Meanwhile, transforming these bio-based epoxy networks to be degradable is a fast developing area.…”

“…Several types of degradable epoxy networks are reported using bio-based building blocks. − One popular strategy is by engineering the networks with labile chemical bonds, such as disulfide, acetal, ester, Schiff base, etc. ,− These labile bonds are either inherently existing in the bio-based building components or in situ formed during the cross-linking. , Sometimes, they exhibit dynamic features, allowing the networks to be reprocessed, and are degradable when subjected to specific chemical or thermal treatments. , For example, epoxidized soybean oil (ESO) has been cured by uniquely structured hardeners, bearing a Schiff base bond or a disulfide bond, and the resulting networks can be degraded in an acidic environment or a reducing environment. , A mono-epoxy resin was prepared from vanillin and cross-linked by different diamines via a concomitant amine-epoxy ring opening reaction and Schiff base formation to have varied mechanical and thermal properties . Due to the presence of Schiff base, these epoxy networks were readily degraded in a 0.1 M HCl aqueous solution .…”

“…As far as we know, there are three reported epoxy networks involving the IV process using petroleum-based epoxy resins and only one study discussed their degradation behavior (Scheme ). ,, For example, our group prepared hardeners from the reaction of sulfur with 10-undecenoic acid for cross-linking DGEBA, resulting in well-toughened strong adhesive networks, which were degradable in hexylamine and methanol solution of Na 2 S. However, degradable epoxy networks from bio-based resins are yet to be explored.…”

Grafting self-immolative poly(benzyl ether)s toward sustainable adhesive thermosets with reversible bonding and triggered de-bonding capabilities

“…In terms of molecular design, a variety of polymeric structures embedded with independent functional moieties that can be orthogonally activated to achieve the desired properties have been proposed. Recent studies have employed dynamic bond exchange, [7][8][9][10][11][12][13][14][15][16] isomerization, [17][18][19] or elimination 15,20,21 for the covalent control of adhesive performance, while non-covalent interactions such as multiple hydrogen bonds or metal coordination have also been used. 6,[22][23][24][25] However, in most cases, the covalent and noncovalent bonds individually function for adhesive properties so it is difficult to achieve rapid and comprehensive control for them; thus, persistent and/or excessive stimulation is oen required, which weakens the energy-efficient re-bonding and/or de-bonding behavior of the adhesive.…”