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It is of great importance to develop epoxy vitrimers with the combination of high performance and versatile recyclability. Herein, two imine-containing hardeners were synthesized from bio-based vanillin and petroleum-based p-hydroxy benzaldehyde. The epoxy resins cured by these two hardeners show high T g (>120 °C), tensile strength (>60 MPa), Young's modulus (>2500 MPa), and good solvent resistance. Owing to the incorporation of imine dynamic covalent bond, the cured epoxy resins are reprocessable and degradable. Notably, the chemical degradation products can be reused to prepare new epoxy resins, thus achieving a closed-loop recycling process. Both the reprocessed and chemically recycled epoxy resins exhibit high-percentage retention of thermal and mechanical properties. Finally, this study demonstrates that the epoxy resin cured by the vanillin-based hardener shows comparable thermal, mechanical, and recycling properties compared with the epoxy resin cured by the petroleumbased counterpart.

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In this work, novel electrospun scaffolds with fibers oriented randomly and evenly in three dimensions (3D) including in the thickness direction were developed based on the principle of electrostatic repulsion. This unique structure is different from most electrospun scaffolds with fibers oriented mainly in one direction. The structure of novel 3D scaffolds could more closely mimic the 3D randomly oriented fibrous architectures in many native extracellular matrices (ECMs). The cell culture results of this study indicated that, instead of becoming flattened cells when cultured in conventional electrospun scaffolds, the cells cultured on novel 3D scaffolds could develop into stereoscopic topographies, which highly simulated in vivo 3D cellular morphologies and are believed to be of vital importance for cells to function and differentiate appropriately. Also, due to the randomly oriented fibrous structure, improvement of nearly 5 times in cell proliferation could be observed when comparing our 3D scaffolds with 2D counterparts after 7 days of cell culture, while most currently reported 3D scaffolds only showed 1.5- to 2.5-fold improvement for the similar comparison. One mechanism of this fabrication process has also been proposed and showed that the rapid delivery of electrons on the fibers was the crucial factor for formation of 3D architectures.