Modeling of Biomaterials for Non-Linear Optical Applications.
Interim rept. 1 Jan 93-1 Jan 94,
VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
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Computational chemistry methods were used to explore the molecular conformations of a variety of optoelectronic biopolymers-spiropyran chromophore systems. An understanding of the molecular structure of such systems is required for the achievement of high x2 or x3 nonlinear optical NLO properties. Studies of the structures of such biologically synthesizable materials that exhibit NLO response contribute insight and understanding needed for the invention of complex novel biomaterials having defined structures and controlled optical properties. The effects of spiropyran chromphore isomerization on poly-L-alanine having the peptide backbone in the alpha-helical or beta-sheet conformations were investigated. Two variations of the spiropyran chromophores on two copolymers, the hexapeptide polygly-ser-gly-ala-gly-ala and the septipeptide polyasp-arg-leu-ala-ser-tyr-leu were also investigated. These polypeptides are compositionally representative of the naturally occurring amino acid sequences in silk and wool, having respectively, the beta-sheet and alphal-helical conformations. The structural possibilities for such materials could be very interesting. The helical or sheet segments could be collinear, and the peptide-chromophore molecules able to order easily, perhaps into a liquid crystalline phase. Furthermore, the presence of the chromophore could prelude crystallization and stabilize the liquid crystalline phase. Upon irradiation with light, formation of the merocyanine could cause the alpha-helix segments to become non-collinean, thus disrupting the packing of the liquid crystalline phase. Not only would the material become colored, its opacity would also change as a result of disruption of the molecular packing.
- Polymer Chemistry
- Theoretical Mathematics