Thesis Details

Thesis Title: Electrostatic Self-assembled Nanolayers on Textile Fibers.
Thesis Author: Gary Kevin Hyde
Abstract: Electrostatic Self-assembled Nanolayers on Textile Fibers. (Under the direction of Juan P. Hinestroza.) This project reports the deposition of nanolayers of poly(sodium 4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) over cotton fibers using the electrostatic self-assembly method (ESA). While glass, silicon wafers, gold coated particles, quartz and mica have dominated the choice of substrates for ESA, the use of textile fibers has been rarely considered. Cotton, in particular, offers a unique challenge to the deposition of nanolayers because of its unique cross section as well as the chemical heterogeneity of its surface. The deposition of the nanolayers involved the preparation of cotton substrates via immersion in 2,3-epoxypropyltrimethylammonium chloride solutions to produce cotton with a high density of cationic groups. The cationic cotton was processed further by repeated sequential dipping into aqueous solutions of PSS and PAH with rinsing between each deposition step. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Transmission Electron Microscopy (TEM) were used to verify the presence of deposited nanolayers. This research work demonstrates the possibility of using the ESA method to tailor the surface of textile fibers at the molecular level by depositing nanolayers of biocidal, charged nanoparticles, non-reactive dyes, and polyelectrolytes in a controlled manner. Preliminary results indicate that the thickness and sequence of the nanolayers can be controlled to tailor and enhance the selectivity, diffusivity, and permeability of the textile fibers while maintaining their comfort and physical properties. Purpose of Research One of the most commonly used methods of surface modification involves the use of multilayer thin films. Electrostatic self-assembly is one of several methods used to alter the surface characteristics of multilayer thin films. Electrostatic self-assembly has been used extensively to deposit nanolayers on substrates made of silica, mica, gold, glass, and titanium. Until now, textile materials have not been explored as substrates for this process. This research work is aimed at determining the appropriate conditions that will allow textile products to be used as substrates for the controlled deposition of nanolayers using electrostatic self-assembly. 1.2 Challenges The electrostatic self-assembly process has not been implemented in textile materials as they pose a number of unique problems that are not found when using traditional substrates such as silicon wafers or gold particles. These problems include non-uniform surfaces and irregular shapes in yarns and fibers. In addition, the different types of fabric formation produce surfaces that are highly non-uniform. Examples of irregular surfaces can be seen in Figures 1-1 and 1-2. 1.3 Research Objectives The primary objective of this research work is to validate the hypothesis that textile materials can be used as substrates for the controlled deposition of nanolayers using the electrostatic self-assembly method. There are also several secondary research questions that will be answered during this study including evaluation of physical and 2 2 chemical methods by which cotton and other textile fibers can be modified in order to support multilayer thin films. Successful deposition of nanolayers onto textile by electrostatic self-assembly will provide a number of different benefits. This process will allow the surface of textile products to be controlled at a molecular level. The use of multilayer thin films will increase the surface functionality of the textiles without making major changes to the weight, bulk, or comfort of the material. In addition, it is possible that this deposition process would greatly reduce the number of chemicals normally needed for textile finishing. The self-assembly process is water-based and it does not require the use of expensive or hazardous solvents. The self-assembly process could also be easily adapted to current textile manufacturing techniques.