Leveraging Itaconic Acid in Microcrystalline Cellulose Reinforced Shape Memory Photopolymers for Sustainable 4D Printing

Abstract

Developing sustainable 3D printable materials that confer competitive mechanical properties as well as advanced properties such as shape memory has remained a challenge. To address these issues, this work investigated the incorporation of economically accessible microcrystalline cellulose reinforcing particles with itaconate surface grafting within itaconated castor oil monomer and isobornyl (meth)acrylate (IBO(M)A) reactive diluent formulations. Using itaconate surface grafted microcrystalline cellulose particles tolerated high reinforcement loading up to 10 wt.%, and yielded improved mechanical properties compared to unmodified particles. Varying the reinforcing particle loading achieved tailorable mechanical properties, while the choice of reactive diluent also led to differing mechanical properties (IBOA: E of 0.86–1.59 GPa, UTS of 14.8–24.7 MPa and IBOMA: E of 1.01–1.39 GPa, UTS of 21–27.7 MPa). Formulations up to 5 wt.% particle loading were 3D printed using masked stereolithography, achieving detailed features and intricate structures with low polymerization shrinkage. The 3D printed polymers displayed efficient shape memory behavior with thermal actuation at 100°C. This work highlights the efficacy of microcrystalline cellulose and its ease of surface modification, the potential to use itaconic acid as a sustainable source of reactive unsaturation in vat photopolymerization additive manufacturing, and that 3D printed materials with a high biobased carbon content that were also mechanically competitive and displayed shape memory capabilities could be readily achieved through facile synthetic pathways.