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 mu m 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.