Synthesis of NLO-Active Surfactants and Investigation of the Effects of Noncovalent Interactions on Molecular Orientation in Multilayer Films

Date of Award

2005

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Johal, Malkait

Keywords

Thin Films, Sufactant, SHG, Synthesis, NLO

Area of Concentration

Chemistry

Abstract

Surfactants of the type X-azo-O-(CH2)10-SO3, where X = -NO2, -CN, and -COCH3, were synthesized and incorporated into multilayer films using the electrostatic self-assembly (ESA) method and the Langmuir-Blodgett technique. The presence of various electron-accepting groups at the alkyl tail termini allowed for variations of the D1t-A properties of the azobenzene moiety for possible applications in nonlinear optics. The novel technique of dynamic wettability variation (DWV) was used to study the in situ adsorption kinetics of the surfactants on the PEl adsorbent. DWV is the first method that employs surface force and contact angle measurements to investigate equilibrium adsorption and surface structure equilibration of ESA films. UV-visible spectroscopy, single-wavelength ellipsometry, and second harmonic generation (SHG) were also used to study the kinetics, multilayer formation, and nonlinear optical properties of the ESA films. Monolayer adsorption of the X-azo-O-(CH2)10-SO3- chromophores followed the Langmuir model. The SHG results of the ESA films are consistent with the expected trends in the D-1t-A properties of the amphiphiles, although the measured nonlinear optical response declined with layer number in all systems studied. The observed blue shift from the bulk solution to the film for both the ESA and LB systems suggests the presence of H-aggregation and 1t-1t interactions among the constituent molecules in the multilayer films. In the LB films, decreasing group dipole moment led to increasing packing density and more significant Haggregation. Preliminary studies using the LB method to construct welldefined multilayer assemblies of X-azo-O-(CH2)10-SO3- gave insight into the interplay between dipolar and 1t-1t interactions and their effect on chromophore alignment.

Rights

This bibliographic record is available under the Creative Commons CC0 public domain dedication. The New College of Florida, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.

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