New chemical resins for SLA-based 3D printers

Advances in additive manufacturing (often referred to as "3D printing" technologies have greatly simplified prototype manufacturing and complex design over the past decade. One particular class of 3D printing, namely stereolithography (SLA) and its variants, has particular appeal due to the ability to create objects with small feature sizes and high resolution. However, most commercially available SLA material components are based on (meth)acrylate-based resin systems that have several disadvantages associated with their use, such as inhibition of polymerisation by oxygen, solvent resistance, and the inability to modify surfaces post-printing. The aims of this work were to prepare new chemical resins for SLA-based 3D printers to reduce the disadvantages associated with (meth)acrylate-based commercial resins. Polymerisation via a thiol-acrylate/alkene/alkyne mechanism can help overcome many of these drawbacks, however, these systems are less studied in the context of SLA 3D printing.

In this work, firstly, we report the design and optimisation of thiol-acrylate resin formulations with a view towards effectively controlling the polymerisation depth of the cured polymer layer. Four different photo-blockers were studied and the use of 1,3-bis(4-methoxyphenyl)propane-1,3-dione enabled optically transparent and colourless printed objects with good resolution to be realised. Taking advantage of ready post-printing surface modification of thiol-acrylate polymers, various hydrophilic, hydrophobic, and fluorescent polymer chains were successfully grafted to the object surface via RAFT polymerisation. Free thiol groups at the surface of offstoichiometric resin formulations were also used to immobilize gold nanoparticles for the catalytic conversion of 4-nitrophenol to 4-aminophenol. Secondly, A new 3D printable resin formulation was developed and optimised from commercially available thiol-alkyne monomers. A 3D device was designed from the resin formulation to remove malachite green (MG) from real water samples collected from tap and river, respectively. The results displayed excellent dye removal efficiency, and >95% dye was removed within 5 min. The 3D printed devices were found to be recyclable and removed 100% dye over 6 times after simple washing with de-ionized water and methanol. Thirdly, new alkyne-based monomers were synthesised in house and optimised to prepare formulations for SLA printing. The prepared materials exhibited better solvent resistance and mechanical properties compared to the acrylate-based formulations. The free alkyne surface groups were utilised for post-print alkyne-azide click polymerisation. The successful development of these resins has resulted in novel systems for stereolithography (SLA) 3D printing. The easily tuneable resin composition and post-print surface modifications make them an attractive candidate for SLA printers as well as hold immense potential for broad commercial applications.