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Photopolymers are fast becoming one of the most popular holographic recording media due to their suitability for a wide range of holographic applications, such as sensors, diffractive optics and data storage. The majority of the investigated water-soluble holographic photopolymers are Acrylamide (AA) based. However, the toxic and carcinogenic nature of AA is a growing concern. In order for photopolymer recording media to be a viable option for holographic applications, efforts must be made to remove any occupational and environmental hazards involved in large-scale material development and device fabrication. The main objective of the work presented here is the development and characterisation of an environmentally friendly photopolymer for holographic applications which uses the non-toxic, non-carcinogenic monomer Diacetone Acrylamide (DA) as a substitute for AA in the photopolymer composition. The new DA photopolymer has been shown to achieve diffraction efficiency values of up to 95 % in transmission mode with refractive index modulation values of 3.5×10-3, and diffraction efficiencies of up to 38 % in the reflection regime with the incorporation of a chain transfer agent and after UV post exposure. Parameters such as shrinkage of the photopolymer layer and rate of polymerisation during the recording process have been quantified. The effect of the incorporation of the additives, namely glycerol and zeolite nanoparticles, on the holographic recording properties of the DA-based material has been investigated. A cytotoxicity comparison between the DA and AA photopolymers has also been carried out. The ability of the new photopolymer material to act as a gas sensor has been demonstrated. For the first time, reflection gratings recorded in the photopolymer have been successfully used as pressure-sensing devices, producing a visible and quantifiable colour change under exposure to different pressures.
Cody, D. (2014) Low-Toxicity Diacetone Acrylamide-Based Photopolymer For applications in Holography. Doctoral Thesis. Technological University Dublin. doi:10.21427/D76C7H