Photopolymer-Based Technologies for 3D Printing and Frontal Polymerization

Photopolymerization has become a widely utilized technique, extensively applied across various fields such as 3D printing, surface coatings, dental composites, and numerous other applications. The first three chapters of this work are dedicated to the development of innovative photoresin formulations aimed at conferring specific properties to the photocured materials or influencing their behavior during the photopolymerization process. The first chapter focuses on the incorporation of dynamic crosslinkers based on boronate ester functionalities into photoresins for vat photopolymerization (VP) 3D printing. These crosslinkers are evaluated as potential candidates to reduce mechanical anisotropy in the resulting 3D-printed structures. The investigation begins with an analysis of the viscoelastic properties of the materials during and after photocuring, followed by 3D printing experiments and a comparative evaluation of the mechanical isotropy of the printed materials against control samples. The results indicate an enhancement in the isotropy of the 3D-printed materials. The second chapter investigates isosorbide-based interpenetrating polymer networks (IPNs) synthesized via photopolymerization. The precursor photoresins for these materials were evaluated for their potential application in vat photopolymerization (VP) 3D printing. Leveraging their ability to fracture in water, isosorbide-based materials were identified as promising candidates for the production of disposable molds in complex-shape carbon fiber manufacturing and injection molding processes. The research focused on testing various formulations composed of two isosorbide derivatives, which were photocured using two principal protocols. A preliminary mechanical characterization of the photocured materials was performed, and prompt disintegration in water was confirmed. Finally, 3D printing trials demonstrated encouraging results but also revealed significant critical challenges. The third chapter focuses on the development of a formulation for fully cationic photoinduced frontal polymerization. This advanced manufacturing technique initiates a curing front by exposing localized regions of the resin to light. Once initiated, the curing front self-propagates, facilitating the polymerization of the entire resin. Typically, this process is achieved by combining cationic photoinitiators with thermal radical initiators, enabling the so-called radical-induced cationic frontal polymerization. In this study, a novel formulation was created by blending two primary epoxy crosslinkers with both a cationic photoinitiator and a thermal cationic initiator. This formulation demonstrated the ability to support both fully cationic thermally induced frontal polymerization and fully cationic photoinduced frontal polymerization. Finally, the last chapter presents a stand-alone topic, focusing on the study of quinoxaline cavitands as potential candidates for the sequestration of poly- and perfluoroalkyl substances (PFAS) from polluted water. PFAS represent an emerging class of persistent micropollutants characterized by hydrophobic, fluorinated tails of varying lengths. Given that quinoxaline cavitands have previously demonstrated the ability to reversibly complex a range of hydrophobic molecules, they emerge as promising candidates for the decontamination of wastewater from PFAS. The study aims to investigate the host-guest complexation of PFAS with well-known quinoxaline-based cavitands, and to design and synthesize new ad hoc receptors. The effective complexation of PFAS with quinoxaline-based cavitands was suggested by 1H and 19F NMR titrations although the precipitation of a salt worsen the quality of the outcomes. Also, the ability of these cavitands to absorb the micropollutants in water was investigated, the results suggest a higher efficiency in removing longer-chain PFAS compared to shorter ones. Research then switched on the development of a new receptor capable of efficiently hosting both long and short-chain PFAS by combining hydrophobic interactions with an ionic bond promoted by the presence of permanent ammonium function on one quinoxaline wall. Preliminary results on to absorption of PFAS in water was investigated leading to promising results for both long and short-chain species.