Type of Document Dissertation Author Sui, Zhijie Author's Email Address firstname.lastname@example.org URN etd-07072004-171316 Title Characterization and Applications of PH-Responsive Polyelectrolyte Complex and Multilayers Degree Doctor of Philosophy Department Chemistry and Biochemistry, Department of Advisory Committee
Advisor Name Title Joseph B. Schlenoff Committee Chair John G. Dorsey Committee Member Randy L. Rill Committee Member Rufina G. Alamo Committee Member Keywords
Date of Defense 2004-05-05 Availability unrestricted AbstractPolyelectrolyte 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.
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