http://repositorium.sdum.uminho.pt/bitstream/1822/21935/1/Optical%20Materials.pdf

Fast thermal cis-trans isomerization of heterocyclic azo dyes in PMMA polymers

In this study, we synthesised two series of cholesteric liquid crystal polymers CPQ and CPZ series. First, we prepared four different monomers ML1 containing a cholesteryl group, ML2 containing a c...

Phase and optical behaviours of chiral-azo liquid crystal polymethylsiloxanes with isosorbide units

In order to get novel photochromic fiber-forming polyamides with liquid crystal (LC), high inherent viscosity and thermal stability properties, two linear azobenzene polyaramides were synthesized by alternative polycondensation reactions of trans-azobenzene-4,4′-dicarbonyl chloride with various diamine monomers without any substituents under low temperature. As expected, the resulting polyamides exhibit high degree of crystallinity (the highest value reaches 52%), inherent viscosity (the highest value reaches 4.26 dL/g), and thermal stability (≤5% weight loss at 350 °C) due to intensively intermolecular hydrogen bonding and extremely symmetric and rigid molecular structures, which were identified by FT-IR spectroscopy and elemental analysis. Moreover, important liquid crystal and photoisomerization properties for optical devices and photochromics fibers spinning are also observed in N,N-dimethylacetamide (DMAc) solutions due to the regular rigid structure and intermolecular hydrogen bonding. The synthesized azo polyamides are suitable for fiber spinning and can be applied in fields of potential optical techniques and novel anti-ultraviolet and photochromic fibers industry at wide temperature ranges.

Liquid–crystal azopolyamides with high thermal stability and inherent viscosity

M Gutierrez1*, A Rodriguez-Cobos1, R E Balderas-Navarro1, M Bello-Jimenez1, J A Alvarez2, G RamirezFlores1, S Guel1, L E Elizalde3 and R Ledezma3 1Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Av. Karakorum 1470, Lomas 4a. Secc. C.P. 78210, San Luis Potosi, S. L. P., Mexico 2Facultad de Ingenieria, Universidad Autonoma de San Luis Potosi, Dr. Manuel Nava #8, Zona Universitaria, C.P. 78290, San Luis Potosi, S. L. P., Mexico 3Centro de Investigacion en Quimica Aplicada, Blvd. Enrique Reyna 140, C.P. 25100, Saltillo, Coahuila, Mexico

http://nopr.niscair.res.in/bitstream/123456789/14523/1/JSIR%2071%288%29%20539-543.pdf

Polymer-based hybrid integrated optical photochromic switch

This paper discusses the absorption spectra of films of new azopolymers and polycomplexes of azobenzene derivatives with cobalt before and during the switching on of an electric field. It has been detected that an external electric field affects the transmission by the films of plane-polarized light at the long-wavelength absorption edge. This effect is caused by spatial reorientation of the dipole moments of azobenzene groups, photoinduced by polarized light in an external electric field. The fact that an electric field affects the transmission of light is explained by the appearance of forces that act on the dipole moments of the azobenzene groups and on the metal ions. The increase of the dipole moment of the azobenzene groups when donor or acceptor substituents are introduced into their composition reduces the influence of metal ions on the electrooptic properties of the polycomplex films.

Electrooptic properties of films of azopolymers and polycomplexes with donor and acceptor substituents

We present our results on a newly synthesized bis-phenylazo derivative, namely bisperfluoroalkylsulfonylamino- arylazomethylene-triphenyl-phosphorane (BAM-TPP). Thin films of BAM-TPP in polymethylmethacrylate (PMMA) matrix were prepared. The films (thickness, d < 60 μm) were exposed to UV-vis light with variable intensity in order to stimulate the photochromic reaction of BAM-TPP. The resulting absorption changes of the BAM-TPP/PMMA films were investigated by spectrophotometry. The absorption spectra reveal that BAM-TPP molecules in PMMA undergo photoisomerization with resulting decrease of absorbance in the range 500–700 nm. Finally, the time response of film transmittance at 514 nm under increasing CW light intensity was recorded, showing that the reverse photochromic process brings the absorbance back to its pristine value. The obtained films thus proved to be suitable for optical switching applications.

Optical switching of a photochromic bis-phenylazo compound in PMMA films

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Optical switching of a photochromic bis-phenylazo compound in PMMA films