60ª Reunião Anual da SBPC

INTRODUÇÃO:

In the last years liquid crystals have been explored in the design of novel molecular functional materials, where the mesophases, structural and optical properties can be varied 1,2. The interacting property of these materials possibly the molecular alignment due to boundary conditions, leading to the obtention of polarized light emission 3.

METODOLOGIA:

The physical properties of a series of light emitting liquid crystal compounds were investigated in solid thin films. These compounds present preferentially smectic and nematic phases between 1250C and 2300C and show good fluorescent properties 4. The films were produced on glass plates via spin-coating, using solutions of 2% (wt.) of the compounds in chlorophorm. The films were then heated until the nematic or smectic phase leading to an anisotropic organization of the molecules inside the film after subsequent crystallization.

RESULTADOS:

The film anisotropy produces photo-emission of polarized light. The absorption and emission spectrums of the heated films present significant differences compared to the non-heated ones. Interesting differences into the organization of the molecules were observed when deposited on anisotropic substrates. In addition, these compounds were dissolved in a commercial liquid crystal (E7 - Merck) and inserted in treated cells constructed with polymer rubbed substrates to induce a specific orientation to the liquid crystal medium. These cells presented also partially polarized photo-emission with dichroic ratios between 4.8 and 7.6.

CONCLUSÕES:

The important result of this work is the possibility of polarized light emission using these materials. In this way we heated spin-coated films and dissolved the luminescent molecules (guest) in commercial liquid crystals (host). References 1 Cristiano, R.; Vieira, A. A.; Ely, F.; and Gallardo, H., Liq. Cryst. 2006, 33, 381. 2 Wang, C. S.; Wang, I-W.; Cheng, K. L.; and Lai, C. K., Tetrahedron 2006, 62, 9383. 3 Tokuhisa, H.; Era, M.; and Tsutsui, T., Appl. Phys. Lett. 1998, 72, 2639. 4 Vieira, A. A.; Cristiano, R.; Bortoluzzi, A. J.; and Gallardo, H.; J. Molec. Struct. 2007, xx,xxx.

Instituição de fomento: UFSC, CNPq and IMMP/MCT

Trabalho de Iniciação Científica

Palavras-chave: liquid crystal, luminescent molecules, polarized light emission

E-mail para contato: nnnathalia@hotmail.com