DLP 3D Printing of Levoglucosenone-Based Monomers: Exploiting Thiol-ene Chemistry for Bio-Based Polymeric Resins

Abstract

Additive manufacturing (AM) is a well-established technique that allows for the development of complex geometries and structures with multiple applications. While considered a more environmentally-friendly method than traditional manufacturing, a significant challenge lies in the availability and ease of synthesis of bio-based alternative resins. In our endeavor to valorize biomass, this work proposes the synthesis of new α,ω-dienes derived from cellulose-derived levoglucosenone (LGO). These dienes are not only straightforward to synthesize but also offer a tunable synthesis approach. Specifically, LGO is first converted into diol precursor, which is subsequently esterified using various carboxylic acids (in this case, 3-butenoic, and 4-pentenoic acids) through a straightforward chemical pathway. The resulting monomers were then employed in UV-activated thiol-ene chemistry for digital light process (DLP). A comprehensive study of the UV-curing process was carried out by Design of Experiment (DoE) to evaluate the influence of light intensity and photoinitiator to find the optimal curing conditions. Subsequently, a thorough thermo-mechanical characterization highlighted the influence of the chemical structure on material properties. 3D printing was performed, enabling the fabrication of complex and self-stain structures with remarkable accuracy and precision. Lastly, a chemical degradation study revealed the potential for end-of-use recycling of the bio-based thermosets.

Keywords: DLP 3D printing; UV-curing; bio-based; levoglucosenone; thiol-ene.

Scheme 1

Synthesis of HO‐LGOL from LGO.

Figure 1

(A) Monomers used for the thiol‐ene formulations; (B) Schematic view of the UV‐curing stage and the chemical degradation step; (C) Chemical reactions involved in the UV‐curing (formation of thioether linkage) and in the degradation (hydrolysis of ester bond).

Scheme 2

Synthesis of functional α,ω‐dienes LGO‐M1 and LGO‐M2 from LGO.

Figure 2

(A) 2D and 3D surface of the conversion and h_peak derived from DoE performed with photo‐DSC test on LGO.M1_4SH; (B) response surface of LGO.M2_4SH formulation for conversion and h_peak in function of UV‐intensity and phr of PhI.

Figure 3

(A) FTIR spectra of LGO.M1_4SH pre and post UV‐curing; (B) spectra pre and post UV‐curing for the LGO.M2_4SH.

Figure 4

Storage modulus trend as a function of the time for (A) LGO.M1_4SH and (B) LGO.M2_4SH at different UV‐light intensities.

Figure 5

(A) DSC thermograms of LGO.M1_4SH (red) and LGO.M2_4SH (green); (B) Storage modulus and Tanδ trend in function of temperature for LGO.M1_4SH (red) and LGO.M2_4SH (green).

Figure 6

Viscosity over time (24 h) in function of the shear rate for LGO.M1_4SH (A) and LGO.M2_4SH (B).

Figure 7

Jacob′s curve obtained for LGO.M1_4SH (red) and LGO.M1_4SH (green).

Figure 8

Resolution over xy‐axis testing for LGO.M1_4SH (A) and LGO.M2_4SH (B).

Figure 9

CAD model of square pyramid (base of 10 × 10 mm² and height of 10 mm), picture of 3D printed object of LGO.M2_4SH, 3D scanner file of the object, and overlay map with scale bar of 100 μm.

Figure 10

3D printed object with LGO.M1_4SH and LGO.M2_4SH. The ring had a diameter of 12.56 mm and height of 7.5 mm. The scale bar unit is 100 μm.

Figure 11

Degradation profile of the LGO.M1_4SH and LGO.M2_4SH in the alkaline environment.