Monochromatic Visible Light “Photoinitibitor”: Janus-Faced Initiation and Inhibition for Storage of Colored 3D Images

Abstract

Controlling the kinetics and gelation of photopolymerization is a significant challenge in the fabrication of complex three-dimensional (3D) objects as is critical in numerous imaging, lithography, and additive manufacturing techniques. We propose a novel, visible light sensitive "photoinitibitor" which simultaneously generates two distinct radicals, each with their own unique purpose-one radical each for initiation and inhibition. The Janus-faced functions of this photoinitibitor delay gelation and dramatically amplify the gelation time difference between the constructive and destructive interference regions of the exposed holographic pattern. This approach enhances the photopolymerization induced phase separation of liquid crystal/acrylate resins and the formation of fine holographic polymer dispersed liquid crystal (HPDLC) gratings. Moreover, we construct colored 3D holographic images that are visually recognizable to the naked eye under white light.

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“…However, in such a case, the conversion rate is rather slow with less than 60% of conversion obtained after 800 s of irradiation. This effect may be attributed partly to the formation of ITX ketyl radicals (ITXH•) which are known to act as terminating agents [19][20]. Addition of a triazine derivative (TA), which acts as oxidizing agent towards the ketyl radical, permits to turn ITXH• into the starting ITX and an additional initiating radical (Scheme 2).…”

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