Chemical and Biomolecular Engineering Research and Publications

 

Date of this Version

May 2006

Comments

The authors of this paper are :James R. Heflin(virginia Tech,Blacksburg), Matthew T. Guzy(virginia Tech,Blacksburg), Patrick J. Neyman (virginia Tech,Blacksburg), Kylie J. Gaskins(virginia Tech,Blacksburg), Charles Brands(virginia Tech,Blacksburg), Zhiyong Wang(virginia Tech,Blacksburg), Harry W. Gibson(virginia Tech,Blacksburg), Richey M. Davis(virginia Tech,Blacksburg), and Kevin E. Van Cott* (University of Nebraska ,Lincoln) This paper was originally published in the journal of "Langmuir" Vol. 22 ,Issue no13 on may 27 2006.All the copy rights © of this paper belongs to American Chemical Society.This article may be downloaded for personal use only any other use requires prior permission of the author and American Chemical Society. The publisher version of this article can be found at langmuir 2006 Any other relevant information about this article can be found at American Chemical Society.

Abstract

A covalent/electrostatic layer-by-layer self-assembly method was used to achieve polar ordering of a water soluble, reactive dye in the fabrication of nonlinear optical (NLO) films. We observed a quadratic relationship between the second harmonic intensity I2 and bilayer number for all films made with Procion Brown MX-GRN, demonstrating that the polar ordering of the chromophores is consistent in each successive bilayer. As the ionic strength of the dye deposition solution was increased to 0.5 M NaCl, the of the films increased by approximately 250% to 50 × 10-9 esu, with a corresponding average chromophore tilt angle of 38. This was attributed to increased shielding of the dye charges which led to higher chromophore density in the bilayers. The electrooptic coefficient for films of 50 bilayers fabricated at 0.5 M NaCl was 14 ± 2 pm/V. Importantly, these films exhibited excellent thermal stability, with only a 10% decrease in (I2)1/2 after 36 h at 85 C and then 24 h at 150 C. Furthermore, the (I2)1/2 recovered completely upon cooling to room temperature. These results with a commodity textile dye point to the potential value of this class of reactive chromophores and this self-assembly method for fabrication of electrooptic materials at ambient conditions from aqueous solutions.

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