Dielectric and Optical Characterization of Polar Polymeric Materials: Chromophore Entrained PMMA Thin Films

Open Access
Author:
Deily, Kevin John
Graduate Program:
Electrical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 21, 2008
Committee Members:
  • Ruyan Guo, Thesis Advisor
  • Michael T Lanagan, Thesis Advisor
  • Joseph Patrick Dougherty, Thesis Advisor
Keywords:
  • electro-optic effect
  • PMMA
  • DR-1
  • thin films
Abstract:
The dielectric and optical response of thin film organic polymer poly(methyl methacrylate) (PMMA) doped with the chromophore N-Ethyl-N-(2-hydroxyethyl)-4-(4-nitrophenylazo)aniline (DR-1) samples were investigated over a wide frequency and temperature range for electro-optic. The DR-1 was directly doped into the PMMA matrix as a guest-host polymer system and three different concentrations of the DR-1 (0%, 5%, and 10% DR-1 by weight) were prepared. Thin film samples of uniform composition, thickness, and smoothness were successfully fabricated for all three concentrations by spin coating. The frequency and temperature dependent dielectric measurements were taken for the samples. The relative dielectric constant and loss factor were to be in good agreement with the reported values for the polymer system. A voltage was applied to the sample in an attempt to align the dipole moments of the chromophore. Breakdown in the film (the capacitance and loss shorting) was a problem with the thinner samples. A polarization verses electric field (P-E) measurement was taken and showed a weak nonlinear response that became more noticeable at elevated electric fields. Also, the biased dielectric measurement was determined by finding the slope of the linear section of the P-E graph. The index of refraction was determined using an ellipsometer. No observable electro-optic coefficient was measured from the samples using a Michelson electro-optic measurement configuration. It was determined that the current polymer samples were not ideal for electro-optic applications. A major contribution of the work was a methodology to extrapolate low frequency dielectric response to GHz and optical frequency.