Odd-even oscillations of SHG efficiencies in twin NLO chromophores

Asha, SK and Ray, Paresh Chandra and Ramakrishnan, S (1997) Odd-even oscillations of SHG efficiencies in twin NLO chromophores. In: Polymer Bulletin, 39 (4). pp. 481-487.

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Abstract

Twin NLO chromophores having two azobenzene units linked by a flexible polymethylene spacer of varying lengths are shown to exhibit odd-even oscillations in their second harmonic generation (SHG) efficiencies, when measured in the powder form. These twin systems were designed to also exhibit liquid cystallinity, and indeed most of them do exhibit a nematic mesophase. The anticipated odd-even oscillations, in both their isotropization transition temperatures (Ti) and isotropization entropies (Delta Si), were also observed. The odd-even oscillation of the SHG efficiencies has been ascribed to a more effective cancellation of mesogenic dipoles in the even twins as compared to their odd counterparts, due to a preferred centrosymmetric packing in the former case. Based on the behaviour of these twin chromophoric molecules, it may be anticipated that such odd-even oscillations will also be observed in the analogous main chain NLO polymers.

Item Type:	Journal Article
Publication:	Polymer Bulletin
Publisher:	Springer
Additional Information:	Copyright of this article belongs to Springer.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	30 Jun 2011 14:31
Last Modified:	30 Jun 2011 14:31
URI:	http://eprints.iisc.ac.in/id/eprint/38330

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