Functional Materials for DLP-SLA 3D Printing Using Thiol–Acrylate Chemistry: Resin Design and Postprint Applications

Three-dimensional (3D) printing techniques have greatly simplified prototype manufacturing and complex design. However, most commercially available stereolithography (SLA) material components are based on (meth)acrylate-based resin systems that have several disadvantages associated with their use, such as inhibition of polymerization by oxygen, solvent resistance, and the inability to modify surfaces post printing. Polymerization via a thiol–acrylate mechanism can help overcome many of these drawbacks; however, these systems are less studied in the context of SLA 3D printing. In this work, we report on the design and optimization of thiol–acrylate resin formulations with a view toward effectively controlling the polymerization depth of the cured polymer layer. Four different photoblockers were studied and the use of 1,3-bis(4-methoxyphenyl)propane-1,3-dione enabled optically transparent and colorless printed objects with good resolution to be realized. Fully enclosed microchannels with diameters as low as 250 μm were successfully printed using this approach. Taking advantage of ready postprinting surface modification of thiol–acrylate polymers, various hydrophilic, hydrophobic, and fluorescent polymer chains were successfully grafted to the object surface via reversible addition–fragmentation chain transfer (RAFT) polymerization. Free thiol groups at the surface of off-stoichiometric resin formulations were also used to immobilize gold nanoparticles for the catalytic conversion of 4-nitrophenol to 4-aminophenol. The tunability of these thiol–acrylate resins for SLA 3D printing and feasible postprint surface modifications make them attractive candidates for commercial applications.