Polyelectrolyte Association and Nanocomposite Application
Fu, Jingcheng (author)
Schlenoff, Joseph B. (professor directing dissertation)
Ma, Teng (university representative)
Dalal, Naresh S. (committee member)
Zhu, Lei (committee member)
Florida State University (degree granting institution)
College of Arts and Sciences (degree granting college)
Department of Chemistry and Biochemistry (degree granting department)
Water soluble polyelectrolytes have gained great interest for their low toxicity and wide applications. Oppositely charged polyelectrolytes (polycations and polyanions) can produce thin multilayers through a layer-by-layer technique and complexes by simultaneously mixing. This dissertation discusses a fundamental study on the driving force of the polyelectrolyte complex mixing and the application of complexes such as nanoparticle imbedded composites. In the first part of this dissertation, the driving force of mixing poly(diallyldimethyl-ammonium) (PDADMA) and poly(4-styrenesulfonate) (PSS) was studied using isothermal calorimetry (ITC). Entropy, rather than electrostatics, turned out to be the driving force of the complex precipitation. A series of Hofmeister anions with PDADMA were used to titrate with PSS in ITC and showed different enthalpies. Studies of attenuated total reflectance (ATR) and Raman spectroscopy on water perturbation difference in PDADMA with different Hofmeister anions showed that the enthalpy difference from anions was caused by defects of water structure (H-bond) in those polycations. The second part of this dissertation discusses the water content effect on the Tg of the polyelectrolyte complexes made of PDADMA-PSS. A layer-by-layer technique was used to build up a multilayer on the surface of an ATR germanium crystal and temperature scans were conducted under different NaCl concentrations. The third part of this dissertation discusses making Fe3O4 superparamagnetic nanoparticle-imbedded polyelectrolyte composites base on PDADMA-PSS. Magnetic nanoparticles with a diameter of approximately 11 nm were synthesized in lab and added to PDADMA-PSS complexes using a two-step mixing procedure. Nano-composites with 0.5 wt%, 2.1 wt% and 4.5 wt% of nanoparticle content were produced and extruded. Some degrees of aggregation of nanoparticles were observed using transmission electron microscopy (TEM). Nevertheless, all three composites showed superparamagnetic behavior at room temperature by superconducting quantum interference device (SQUID) tests. Nanocomposites were heated up to 102 °C using radio frequency. Tensile strength and toughness increased with the nanoparticle content in the nanocomposites. The final part of this dissertation compares 18 different polyelectrolyte complexes made with different polyelectrolytes. Different conditions were used to precipitate and extrude the complexes. Doping constants and diffusion coefficient for extruded complexes were tested and compared. The "toughness" of the complexes were compared and an approximation ranking was given to show the strength of a polyelectrolyte interacting with its oppositely charged polyelectrolytes. Radio labeling methods were used to test the stoichiometry of the complexes.
Association, Nanocomposites, Polyelectrolyte
March 27, 2017.
A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the Doctor of Philosophy.
Includes bibliographical references.
Joseph B. Schlenoff, Professor Directing Dissertation; Teng Ma, University Representative; Neresh Dalal, Committee Member; Lei Zhu, Committee Member.
Florida State University
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