Spatial control of curing kinetics in thiol-ene-systems through antagonistic photoreactions

The use of two wavelengths to activate different photoreactions in a resin system has recently attracted much attention in the scientific community. Here, wavelength orthogonal photochemistry was used to spatially control the curing kinetics of the thiol-ene photopolymerization reaction. Antagonistic photochemical control is successfully applied to thiol-ene polymerization. In the investigated resin (pentaerythritol-tetrakis(3-mercaptopropionat); PETMP and triallyl-triazine-2,4,6(1H,3H,5H)-trione; TATO) system, radical curing is activated by a type II photoinitiator at 450 nm, while light at 365 nm is used to photorelease a base, resulting in an inhibition of the curing reaction. The antagonistic nature of these photoreactions is demonstrated in laser writing with minimum feature sizes below 0.5 µm as well as in grey scale patterning experiments. Spatially controlled inhibition and retardation of the thiol-ene curing reaction on a sub-micron scale have potential applications in advanced large area lithography, e.g. interference lithography.