Date of Award
Doctor of Philosophy (PhD)
Materials Science and Engineering
Mefford, O. Thompson
This dissertation presents the building and study of a "universal" enrichment polymer layer system (EPLS). Thin polymer films have been utilized as enrichment layers for evanescent waveguide chemical sensors. The chemical nature of the polymer provides affinity which promotes the analyte to be absorbed. Having one highly sensitive polymer layer is suitable for a single target volatile organic compound (VOC). Here, the development of multi-layered and multi-component thin polymer films has been done to allow for more diverse affinity. Several parameters were identified to make the EPLSs suitable as enrichment layers for chemical sensor devices. The evanescent sensor devices used chalcogenide (ChG) glass, which is an infrared (IR) transparent material, and the principle of attenuated total reflection (ATR). This allowed the use of mid-IR spectroscopy to identify the absorbance of the absorbed VOCs in the polymer films. Changes of the absorbance due to influences of the EPLS were observed. These changes have not been reported before by researchers but can potentially be used to aid in fast and accurate identification of chemical compounds. The thicknesses of the total EPLS were kept to ≤ 30 nm so the evanescent wave would not be completely absorbed by the EPLS and absorbed VOC. Poly(glycidyl methacrylate) (PGMA) was a binding polymer for all EPLSs. As such, a single component PGMA film was tested to understand how the polymer influences the EPLS. Sensitivity to VOC concentration was conducted by mixture analysis and dilution by nitrogen gas in dynamic flow conditions. Comparison of each EPLS is done as well as to determine wavelengths of interest. Polymers were applied to ChG microdisk and amorphous silicon microring resonators and were found to increase sensitivity versus no polymer film at all. Two distinct layered enrichment nanoscale systems were synthesized and characterized - a six layer system and a five layer system. The polymer layered systems were characterized by atomic force microscopy, ellipsometry, and IR spectroscopy. Polymers utilized were PGMA, poly(acrylic acid), 60% epoxidized poly(butadiene), and poly(4-vinyl pyridine). In-situ ellipsometry was done to determine the swelling fraction of the film. In-situ attenuated total reflection (ATR) FT-IR spectroscopy was used to identify absorbance differences. Each EPLS proved to promote unique interactions which brought about differences in VOC absorbance in the mid-IR region.
Giammarco, James, "Synthesis and Characterization of Multi-Component Enrichment Polymer Layers for Chemical Sensor Applications" (2013). All Dissertations. 1205.