Chiral Power Change upon Photoisomerization in Twisted Nematic Liquid Crystals

SABRINA SIMONCELLI; PEDRO F. ARAMENDÍA

SPECTROCHIMICA ACTA A: MOLECULAR AND BIOMOLECULAR SPECTROSCOPY

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Lugar: Amsterdam; Año: 2015 vol. 142 p. 94 - 100

0584-8539

In this work, we use the photoisomerization of azobenzenes, a phenanthrospirooxazine, anda fulgide in a twisted nematic liquid crystalline phase to change the chiral twisting power of thesystem. The changes are probed by the rotatory power of linearly polarized light. Time resolved andsteady state experiments are carried out. The chiral change and the photoisomerization process havesimilar characteristic recovery times and activation energy, thus probing that the change is induced bythe modification in the chemical composition of the photochromic dopant system. The amplitude of thelight twisting power change correlates with the order change in the LC but not with the modification inthe absorption characteristics of the system. This indicates that the driving force of the chiral change isthe microscopic order modification in the LC phase that affects the helical pitch of the phase.