Unexpected self-assembly of carbon dots during digital light processing 3D printing of vanillin Schiff-base resin

Abstract

Bio-based and recyclable composite thermosets were obtained through digital light processing (DLP) 3D printing by dispersing cellulose-derived carbon dots (CDs) in a photocurable vanillin Schiff-base resin. The exposure of CDs to DLP induced a partial reduction of the oxygen functionalities and a self-assembly of CDs into micrometric fibers embedded in the thermoset matrix. A comparison with the vanillin Schiff-base thermoset, illustrated lower transition temperature from the glassy to the rubbery state and inferior shape memory properties for the CD containing thermoset. This is ascribed to a lower crosslinking density due to the replacement of the covalent interactions of the thermosets with supramolecular interactions generated inside the microfibers and between the microfibers and the surrounding matrix. This can also explain the inferior mechanical rigidity of the composites with respect to the single component thermosets. However, the supramolecular interactions endow the composites with better mechanical and chemical recyclability with an almost complete preservation of the original mechanical properties.