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Optical Gain from Polyfluorene Keto Defects in a Liquid Crystal Mixture

par Bolis, Serena ;Celebrano, Michele;Ghirardini, Lavinia;Finazzi, Marco;Botta, Chiara;Beeckman, J.;Kockaert, Pascal ;Virgili, Tersilla
Référence FISMAT2015 (28 September-2 October 2015: Palermo (Italy))
Publication Non publié, 2015-10-01

Communication à un colloque

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Résumé :

In this work we show, by means of confocal photoluminescence measurements and fspump-probe spectroscopy, that a large polarized stimulated emission from polyfluoreneketo defects is obtained in a mixture of polyfluorene with a nematic low molecularweight Liquid Crystal (LC). This mixture is placed in 9-micron thick cell constituted bytwo polyamide-coated plates rubbed to induce a macroscopic optical anisotropy of theLC molecules. In this blend a peculiar phase separation generates an ordered networkof LC-rich micro-domains with the most of the polyfluorene chains placed on the microdomainsboundaries. These well-defined phase boundaries have an anchoring effectso strong that the polymeric chains are forced to align parallel to them, despite thealignment of the nematic LC induced by the rubbing layers. The isolation andorientation of the polymeric chains reveal the possibility to obtain polarized optical gainfrom the keto defect. The results are expected to have broad implications in the fieldsof photophysics and material design of polyfluorene materials, since the fomation offew fluorenone units can be seen not anymore as a form of degradation of thepolyfluorene but as an improvement of the physical properties of this interestingpolymer.