Abstract: Polydiacetylenes (PDAs) are attractive materials forboth electronic and photonic applications because oftheir highly conjugated electronic structures. Theyhave been investigated for applications as both 1Dconductors and nonlinear optical (NLO) materials. Oneof the chief limitations to the use of PDAs has beenthe inability to readily process them into useful formssuch as films and fibers. In our laboratory we havedeveloped a novel process for obtaining amorphous filmsof a PDA derived from 2- methyl-4-nitroaniline usingphotodeposition with UV light from monomer solutionsonto transparent substrates. Photodeposition fromsolution provides a simple technique for obtaining PDAfilms in any desired pattern with good optical quality.This technique has been used to produce PDA films thatshow potential for optical applications such asholographic memory storage and optical limiting, aswell as third-order NLO applications such asall-optical refractive index modulation, phasemodulation and switching. Additionally,copolymerization of diacetylenes with other monomerssuch as methacrylates provides a means to obtainmaterials with good processibility. Such copolymers canbe spin cast to form films, or drawn by either melt orsolution extrusion into fibers. These films or fiberscan then be irradiated with UV to photopolymerize thediacetylene units to form a highly stable cross-linkedPDA-copolymer network. If such films are electricallypoled while being irradiated, they can achieve theasymmetry necessary for second-order NLO applicationssuch as electro-optic switching. On Earth, formation ofPDAs by the above mentioned techniques suffers fromdefects and inhomogeneities caused by convective flowsthat can arise during processing. By studying theformation of these materials in the reduced-convection,diffusion- controlled environment of space we hope tobetter understand the factors that affect theirprocessing, and thereby, their nature and properties.Ultimately it may even be feasibly to conduct spaceprocessing of PDAs for technological applications. !15
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