Characterization and Applications of Ph-Responsive Polyelectrolyte Complex and Multilayers

• Other Authors: Sui, Zhijie (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Chemistry
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-0401

Polyelectrolyte complexes (PECs) have received a growing interest since the early sixties. PECs have been used for large-scale industrial applications and have demonstrated enormous potentials in various fields such as coatings, binders and flocculants. Using the Layer-by-layer deposition technique, an ultrathin polyelectrolyte multilayer coating was first built in 1990 and soon both theoretical and practical interest in these coatings were growing exponentially. In the first part of this dissertation, studies were focused on the fundamental properties of polyelectrolyte multilayer and complex systems, such as the effect of molecular weight of polyelectrolytes and the effect of ionic strength on the multilayer buildup and the thermodynamics of the polyelectrolyte complexation. In the second part, a series of pH-tunable polyelectrolyte complexes and pH-responsive multilayers were designed and studied. Random copolymers composed of pH-independent "strongly" charged parts and pH-dependent "weakly" charged parts were introduced for making pH-tunable polyelectrolyte complex and pH-responsive multilayers. A systematic study of the pH induced change of multilayer configuration, including film decomposition, phase separation and surface charge rearrangement, was conducted. It was found, by varying the mole percent of the weakly charged segments in the multilayers, the outcome of external pH changes on the multilayers varied from total film decomposition, to forming microporous surface, and finally to yielding a surface-charge-tunable multilayer, which meant the ability of controlling the surface charge polarity and density via pH. The outcome was essentially due to the combination of two types of charge interaction, charge extrusion and charge expulsion. It was also demonstrated that, with the use of the pH-responsive polyelectrolyte multilayer coatings to modify the substrate surface, the adsorption and release of biomaterials, such as proteins, could be controlled by varying the surface charge property via simple pH switch. Potential applications of this finding were proposed in the dissertation. === A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. === Degree Awarded: Summer Semester, 2004. === Date of Defense: May 5, 2004. === Polyelectrolyte, PH-Responsive, Multilayers, Complex === Includes bibliographical references. === Joseph B. Schlenoff, Professor Directing Dissertation; Rufina G Alamo, Outside Committee Member; John G. Dorsey, Committee Member; Randy L. Rill, Committee Member.