Linalool Derivatives for Natural Product-Based 4D Printing Resins
David Merckle, E. Constant, Andrew C. Weems
Abstract
The use of green alternatives to petrochemicals from renewable feedstocks is of great interest globally, especially within additive manufacturing efforts. To this end, the utilization of the terpenoid linalool is presented for photopolymer resins 3D printed using digital light processing (DLP) with thiol-ene click chemistry. Linalool derivatives are made from single-step modifications, providing multiple greener alternatives to current acrylate photopolymers, and are characterized based upon rheology, thermomechanical, and shape memory properties. The use of aliphatic and aromatic diisocyanates to produce tetra-functional monomers is demonstrated to provide tunability to the photoreactivity/gelation time as well as significantly enhancing the tensile properties (2–3 orders of magnitude increase in elastic modulus) and thermal properties (glass transition temperature increase from ∼12 °C for linalool to 75 °C for the isophorone diisocyanate-containing linalool urethane derivative) and 4D behavior, in this case shape memory response. Ultimately, the derivatives are shown to be better candidates for DLP-type 4D printing of complex prototypes, using a porous cubic structure to demonstrate the additive manufacturing potential of this simple material platform.