A commercially important polyelectrolyte, xanthan, was chosen for a systematic analysis of the relationship between molecular conformation and surface properties. In the first study the effects of ionic strength, xanthan concentration and temperature on the xanthan molecular conformation were investigated by potentiometric titration. The effects of the same factors and of the degree of ionization on the surface tension of xanthan solutions were then analyzed by the drop weight and the Wilhelmy plate methods. Potentiometric titration studies showed that the ordered xanthan conformation is stabilized mainly by hydrogen-bonds which can be disrupted by increasing the electrostatic potential of the molecule or by increasing the solution temperature. Adding salt or increasing the xanthan concentration did not affect the secondary structure. Surface tension studies showed that the random coil is more surface active than the helix xanthan structure. The rate of xanthan adsorption at the interface of the random coil is also faster than that of the helix structure. Surface tension was also shown to be dependent on the electrostatic potential of the polyelectrolyte. Added salt screened the electrostatic repulsive force and therefore decreased the surface tension of xanthan solution. / Graduation date: 1987

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 126-133).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 144-146). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 153-156). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--Lehigh University, 2001. / Includes bibliographical references and vita.

Conjugated polyelectrolytes (CP) show interesting electrical and optical properties for organic electronics as well as for life science applications. Their possibilities of supramolecular assembly with nanowire like misfolded proteins, amyloids, as well as synthetic polypeptides or DNA forming conducting nano composites is highly interesting as being a truly bottom up approach for fabrication of OLEDs, photovoltaic’s as well as logic devices. A special class of CPs is that of electroactive cojugated polymers (ECPs), which, due to their structure, will exhibits a unique combination of properties, including the following; electrically conducting, ability to store an electric charge and ability to exchange ions. The positive or negative excess charge can be introduced into the conjugated polymer by means of chemical or electrochemical oxidation/reduction (a process called doping) following the polymerization reaction. In order to preserve overall electroneutrality of the polymer during introduction of excess charge, ionexhange processes occurs between the polymer phase and the surrounding electrolyte solution. This charge/discharge process can be utilized for application such as; pseudo super capacitors (energy storage through oxidation/reduction processes), electro mechanical actuators (convert electrical energy to mechanical energy) and sensors (converts a chemical signal to electrical conductivity). In this thesis we describes the synthetic challenges with ECPs for applications vide supra. These mostly relates to solubility, ionic functionalization, conductivity and macromolecular properties such as size and shape of the ECPs. The key requirement in the synthesis of ECPs is that the conjugated nature of the monomer is conserved in the synthesis process and that insertion of excess charge (doping) can be obtained. This limits both the choice of monomer and the choice of polymerization process. Monomers of great complexity have been synthesized with this careful goal in mind. Furthermore, the development of novel monomers must also target the appropriate functionality for polymerization. As such, most ECP monomers are electron-rich molecules with pendant groups containing pyrroles, thiophenes, or 3,4-ethylenedioxythiophenes. These three well known ECP monomers are excellent additions to conjugated systems as they typically enable electrochemical polymerization and direct the polymerizations toward linear polymers with good stability towards doping. The first topic of this thesis we demonstrate how we can obtain water soluble ECPs with good electrical conductivity by controlling the polymerization techniques and proper ionic functionalization of the monomer. We also show how these polymers can be incorporated by self-assembly with biomolecular templates, such as, DNA and amyloid fibrils, thus generating novel electrically conductive nanowires. The second topics of this thesis demonstrate how hydrogels of ECPs can be used as bioand charge storage materials, were we demonstrate electronically controlled cell release for biology applications. Both applications are based on ECPs ability to ionexhange processes during electrochemical redox reactions. As well as ions, solvent and other neutral molecules may enter the film during charge/discharge processes. This cause a swelling or shrinking of the ECP films and the expansion and contraction of the polymer network in conjugation with the sorption/desorption of solvent molecules and ions can be described in terms of mechanical work. In the first case we were able to synthesize a water soluble ECP with high amphiphilic character. The polymer was immobilized onto a flexible electrode, suitable for cell growth and subjected to a cell growth media. When the desired cell layer was formed we applied a potential to the flexible electrode. This resulted in that the mechanical work of the immobilized ECP during the applied potential overcame the week adhesive forces to the flexible electrode, which resulted in super swelling and disintegration of the ICP and the cell layer could be harvested. In the second case the possibilities of using synthetically modified ECPs as a dopant during electropolymerization of another ECP monomer to obtain a polymer integrated network with high charge density and good charge transport properties. We demonstrate how this polymer network can be used as porous electrodes suitable for supercapacitors.

Gao Jun. / "November 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Graduation date: 1997