Biobased Reversible Cross-Linking Enables Self-Healing and Reprocessing of Epoxy Resins

Abstract

The rapid development of thermosetting polymers contributes strongly to environmental pollution, petrochemical resource consumption, and increasing carbon dioxide emission. Introducing a reversible supramolecular cross-linking network into the thermosetting polymer to endow it with reprocessability and self-healing ability is highly attractive for the reduction of fossil fuel consumption. Despite the tremendous advancement in recyclable thermosetting polymers, using biobased materials to construct reversible cross-links, which can realize the high biomass carbon content of materials, remains challenging. Here, we present a selfhealing and reprocessable epoxy resin enabled by biobased multiple hydrogen bonds between biological tannic acid and chitosan. The binding energy simulation demonstrates that effective hydrogen bonds are constructed in the epoxy resin. The resultant supramolecular cross-linked epoxy resin shows improved mechanical properties (tensile strength increased by two times, toughness increased by 2.7 times), high self-healing efficiency (104% toughness recovery) at room temperature, and excellent reprocessability (109% toughness recovery). We envision that the proposed biobased reversible cross-linking strategy will be useful in the greening and recycling of various thermosetting polymers, such as rubbers, crosslinked plastics, etc.

Self-Healing Bimodal Sensors Based on Bioderived Polymerizable Deep Eutectic Solvent Ionic Elastomers

“…Conversely, the intensity at 3108 cm –1 attributed to hydrogen-bonded −NH groups gradually decreases with a blue shift, and the hydrogen bonds related to CO also gradually dissociate (Figure S7). , These spectral features indicate the formation of −OH hydrogen bonds and the dissociation of −NH and CO hydrogen bonds during the warming process. ,− Since −NH and CO groups are, respectively, attributed to PDA and IA, this suggests that PDA@CNC has a possible weakening of the inherent −OH hydrogen bonds in IA/ChCl PDES to some extent but established stronger hydrogen bonding interactions with IA molecular chains at room temperature. Further probing of the ν­(C–N) shifts of PDA and ChCl reveals that an increase in temperature leads to a greater preference for IA binding to ChCl, while the interaction with PDA is weakened (Figure f,i) .…”

“…The characteristic peaks at 3412 cm –1 attributed to the −OH group red-shift to 3343 cm –1 with increasing temperature (Figure e). Conversely, the intensity at 3108 cm –1 attributed to hydrogen-bonded −NH groups gradually decreases with a blue shift, and the hydrogen bonds related to CO also gradually dissociate (Figure S7). , These spectral features indicate the formation of −OH hydrogen bonds and the dissociation of −NH and CO hydrogen bonds during the warming process. ,− Since −NH and CO groups are, respectively, attributed to PDA and IA, this suggests that PDA@CNC has a possible weakening of the inherent −OH hydrogen bonds in IA/ChCl PDES to some extent but established stronger hydrogen bonding interactions with IA molecular chains at room temperature.…”

“…41 The characteristic peaks at 3412 cm −1 attributed to the −OH group red-shift to 3343 cm −1 with increasing temperature (Figure 2e). Conversely, the intensity at 3108 cm −1 attributed to hydrogen-bonded −NH groups gradually decreases with a blue shift, 48 and the hydrogen bonds related to C�O also gradually dissociate (Figure S7). 49,50 These spectral features indicate the formation of −OH hydrogen bonds and the dissociation of −NH and C�O hydrogen bonds during the warming process.…”

Functional Epoxy Elastomer Integrating Self-Healing Capability and Degradability for a Flexible Stretchable Strain Sensor

“…The mechanical and thermomechanical performances of the PEG-SS 8 -ESO y ( y = 0.1, 0.2, 0.3, and 0.4) elastomers were also studied (Figure S4b,c). Compared with relevant self-healing epoxy composites and bio-based materials, the PEG-SS x -ESO 0.2 ( x = 4, 6, 8, and 10) elastomers exhibited lower T g , higher tensile stress, and elongation at break (Figure h). ,,,− Meanwhile, the crosslinking densities ( ν c ) of the PEG-SS x -ESO 0.2 ( x = 4, 6, 8, and 10) elastomers were also calculated according to the storage modulus at the rubbery plateau ( T g + 40 K). The ν c of all of the samples were in a narrow range of 205.7–222.1 mol/m 3 (Table S4).…”

A Polyvinyl Alcohol–Tannic Acid Gel with Exceptional Mechanical Properties and Ultraviolet Resistance

“…Tannic acid is a natural polyphenol compound. Tannic acid with catechol groups can easily form hydrogen bonds and crosslink domains with other active groups [ 1 , 25 , 26 ]. Nevertheless, because tannic acid possesses strong free-radical scavenging ability, its free-radical polymerization is inhibited and retarded [ 1 ].…”