Evolution of Self-Assembled Lignin Nanostructure into Dendritic Fiber in Aqueous Biphasic Photocurable Resin for DLP-Printing

Abstract

The design of lignin nanostructures where interfacial interactions enable enhanced entanglement of colloidal networks can broaden their applications in hydrogel-based materials and light-based 3D printing. Herein, an approach for fabricating surface-active dendritic colloidal microparticles (DCMs) characterized by fibrous structures using nanostructured allylated lignin is proposed for the development of lignin-based photocurable resins. With allyl-terminated surface functionality of 0.61 mmol g−1, the entanglement between lignin-DCM fibrils with a size of 1.4 µm successfully produces only lignin-based hydrogels with structural integrity through photo-crosslinking. The colloidal network of lignin dendricolloids reinforces the poly(ethylene glycol) (PEG) hydrogels during a digital light processing (DLP) 3D printing process by generating bicontinuous morphologies, resulting in six-fold increases in toughness values with respect to the neat PEG hydrogel. The dual effectiveness of photoabsorption and free-radical reactivity of lignin-DCMs allow the light-patterning of rather dilute PEG hydrogels (5–10%) with high geometric fidelity and structural complexity via DLP 3D printing. This study demonstrates a green and effective strategy for the design of 1D lignin-DCMs that increases the versatility of the nanostructured biopolymer, opening up numerous opportunities for formulating functional hydrogels with robust structure-property correlations.