Malleable and recyclable thermoset network with reversible β‐hydroxyl esters and disulfide bonds

Abstract

By combining bifunctional diglycidyl ether of bisphenol A (DGEBA) and trifunctional tris(4-hydroxyphenyl) methane triglycidyl ether (TMTE) epoxy monomers, along with 4,4 0 -dithiodibutyric acid (DTDBA) as a carboxylic acid, a variety of novel reprocessable and recyclable thermoset polymers are synthesized. The crosslinked network structures with different crosslinking densities are produced by changing the mixing ratio between DGEBA and TMTE, resulting in changes in mechanical and thermal properties of the final products. The stress relaxation and self-healing experiments confirmed that all of these polymeric materials have covalent adaptable networks in their microstructures and perform reversible transesterification processes inside a polymer network. These thermoset polymers are completely decomposed in solution by disulfide-thiol reduction of DTDBA with reversible cleavage or coupling capability in the presence of reducing agent, allowing chemical recycling capability into the thermoset polymer network.

Designed to Degrade: Tailoring Polyesters for Circularity

“…The presence of disulfide linkages enabled chemical recycling under mild conditions in the presence of reducing agent 2-mercaptoethanol. The thermoset with only ester bonds remained stable under the same conditions …”

“…Research with regard to chemical recycling and degradation of disulfide containing polymers has mainly focused on the synthesis of recyclable thermosets. In this regard, a series of novel recyclable thermosets were designed to have ester and disulfide linkages, using simple condensation and epoxy chemistry . The epoxy ester thermosets were synthesized by reacting 4,4′-dithiodibutyric acid (DTDBA) with two epoxy monomers; difunctional bisphenol A diglycidyl ether (BADGE) and trifunctional triphenylolmethane triglycidyl ether (TMTE), to form thermosets with ester or ester and disulfide linkages, varying in crosslink density (Figure ).…”

Role of Cyclodextrin Cross-Linker Type on Steroid Hormone Micropollutant Removal from Water Using Composite Nanofiber Membrane

“…Despite the widespread use of EP for βCD cross-linking, its toxicity and carcinogenicity have been documented, , rendering it unsuitable for water treatment applications. Consequently, alternative and more biocompatible cross-linkers have been reported in the literature for βCD cross-linking. − Triphenylolmethane triglycidyl ether (TMTE) and trimethylolpropane triglycidyl ether (TPTE) have been selected in this study as alternative cross-linkers based on characteristics of lower toxicity, commercial availability, and similar epoxy groups suitable for cross-linking reactions, as present in EP. − TMTE and TPTE have been reported as cross-linkers in biomaterials including dental materials − and drug delivery materials. , Chung et al reported TMTE cross-linked photocurable material that aimed to be applied in dental applications showing low curing shrinkage, low water sorption, and low water solubility. Suner et al reported the biomaterials containing TPTE, which showed fast enzymatic degradation of 80–90% using pectinase and amyloglucosidase.…”

Research on Toughening Polylactic Acid by an Epoxy Soybean Oil Curing Network Based on Dynamic Cross-Linking

“…Dynamic reversible reactions are founded upon the presence of reversible groups within the polymer structure, wherein internal chemical bonds can be disrupted and reorganized under specific conditions. This phenomenon enables the polymer to exhibit reversible flow and self-repair capabilities and facilitates recycling. − Furthermore, certain resins utilize dynamic reversible reactions to establish reversible three-dimensional networks internally, leading to structural modifications and conferring exceptional properties upon the material, making it suitable for specific applications. Notable dynamic reversible bonds encompass ester bonds, − disulfide bonds, , silyloxy bonds, , and imine bonds, , among others.…”