Dynamic network based on eugenol-derived epoxy as promising sustainable thermoset materials

Abstract

Permanently crosslinked polymer networks, such as fully cured thermosets derived from fossil-based epoxies, cannot be reuse after damage and/or recycled since they cannot be reprocessed by heating or solubilization as non-crosslinked thermoplastics. As a result, they are not really sustainable materials, generating non-renewable resources consumption, CO 2 emissions and plastic pollution. Herein we employed a strategy to tackle the lack of sustainability in conventional thermosets by the development of a promising partially biobased epoxy for numerous applications, integrating a covalent adaptable network using associative dynamic chemistry and catalyst free mechanism. This strategy is based in two sustainable approaches. First, vegetal biomass has been used as a renewable resource for the synthesis of epoxy systems from epoxidized eugenol oil. Then, the crosslinking reaction with an diamine integrating disulfide bonds to attain a thermally induced reorganizable eugenol-derived epoxy network in a dynamic way by disulfide metathesis reaction. The viscoelastic behavior characterization of eugenol-derived epoxy network displays a fast macroscopic flow with a stress relaxation time of 37 s at 230 °C, suggesting an interesting melt-reprocessability of this network at high temperatures in short times. Moreover, this strategy has a strong potential for the progress of sustainable plastic applications as yield a synthetic procedure to develop stiff thermosets (storage modulus of around 1 GPa at glassy state) with high renewable carbon contents (around 70 wt%), enhanced thermal properties (T g of around 190°C) and additional properties such as promising reshaping, repairing and recycling capability.

Aromatics from Lignocellulosic Biomass: A Platform for High-Performance Thermosets

“…Fortunately, recent advances in polymer chemistry have enabled the fabrication of covalent adaptable networks (CANs) and the incorporation of degradable linkages to produce materials that, like conventional thermosets, are dimensionally stable under most thermal, mechanical, or chemical stress but are reprocessable, repairable, weldable, or degradable under external stimuli, such as heat, ultraviolet light, and pH. ,− CANs also could address some of the sustainability challenges around waste management by increasing the useful lifetime of next-generation thermoset materials and enabling facile recycling . For example, imine-based vitrimers, a subset of CANs, often employed in self-healing hydrogels, leverage reversible bonds formed through an associative, dynamic exchange reaction mechanism between aldehydes and amines. − Several types of reversible chemistries are shown in Figure , including associative (e.g., imine exchange, transesterification, , disulfide exchange, , transcarbamoylation , ) and dissociative (e.g., Diels–Alder (DA), , cyclic carbonate aminolysis , ) reactions for CANs and degradable linkages (e.g., spiro acetals) for thermosets that selectively break down.…”

Synthesis and characterization of new bio-based poly(acylhydrazone) vanillin vitrimers

“…In recent years, products derived from renewable resources have attracted huge interest in materials science to reduce the use of petrochemical compounds as well as to find greener synthetic routes to avoid the depletion of fossil resources. The researchers have focused their attention on synthesizing vitrimeric materials based on compounds derived from biomass such as catechol, 27 eugenol, 28,29 or vanillin. 30,31 In particular, vanillin (4-hydroxy-3-methoxy benzaldehyde) is not only one of the most important aromatic compounds used in food, beverages, perfumes, and pharmaceuticals, but it is also very interesting as a feedstock for the development of materials due to its phenolic and aldehyde groups that can be further modified to get the suitable functionality.…”

Recent progress in bio‐based eugenol resins: From synthetic strategies to structural properties and coating applications

“…The amine hardener such as non‐dynamic 3,3′‐diaminodiphenyl sulfone (DDS) and dynamic 4‐aminophenyl disulfide (DSA), DSA containing disulfide bonds, were used for the curing (Figure 8). 55 In the DSC study, the uncured resin displayed T g around 7°C along with an exothermic peak at 185°C. After fully cross‐linking TEUP‐epoxy/DSA, the exothermic peak has disappeared.…”