Synthesis and thermal behavior of new liquid crystals arylaldoxime esters

• Autor(a) principal: Tavares,Aline
• Data de Publicação: 2012
• Outros Autores: Arruda,Bárbara C., Boes,Elvis S., Stefani,Valter, Stassen,Hubert K., Campo,Leandra F., Bechtold,Ivan H., Merlo,Aloir A.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532012000500013
• topic: arylaldoxime esters; liquid crystals; infra-red analysis; isoxazolines

We report the synthesis of a series of liquid-crystalline materials based on arylaldoxime esters and the characterization of these materials by ¹H, 13C NMR, ATR/FT-IR spectroscopy and elemental analysis. The chemical stability and liquid-crystalline as well as photophysical properties of the compounds are described being dependent on the heating/cooling cycles. The changes in chemical stability and the liquid crystals properties of arylaldoxime esters were observed during these thermal cycles by IR analysis. All samples underwent a thermal degradation yielding the corresponding nitriles and carboxylic acid as evidenced by IR and ¹H NMR spectra. Due to the decomposition process, information about the mesomorphic behaviour is lost. The UV-Vis absorption spectra in solution display three absorption bands between 230 and 340 nm. The fluorescence spectra exhibit a broad and structureless emission band located at 430 nm. Ab initio calculations were performed to obtain information on the molecular structure and properties of the title compounds.