A. Application of Polymeric Quaternary Ammonium Surfactant Clay Intercalates in Triphase Catalysis
A series of polymeric quaternary ammonium layered silicate catalysts were synthesized through intercalation reaction of poly(propylene glycol) (POP) amine and polyethyleneimine (PEI) salt with Na-montmorillonite (MMT). The resulting heterogeneous catalysts were then utilized to perform triphase catalysis to carry out various nucleophilic substitution reactions. In these reactions, n-butyl bromide was converted to n-butyl chloride, n-butyl iodide and n-butyl acetate by using the appropriate nucleophile. All the catalysts were characterized using x-ray powder diffraction analysis as well as infrared spectroscopy prior to their use. Pseudo first order kinetics was observed for all the substitution reactions. Reasonable catalytic activities were observed for all the catalysts. However, much higher catalytic activity was anticipated using these novel catalysts due to their multiple catalytic sites within the polymeric backbone. The catalytic activity of these catalysts was even lower than traditional quaternary ammonium catalyst such as tetraoctyl ammonium bromide (TOABr) when it was intercalated in the MMT clay. There may be several factors involved in the observed catalytic activities of these polymeric quaternary ammonium layered silicate catalysts. Factors such as higher hydrophobicity exerted via polymer structure, orientation of polymer on the clay surface and polymer encapsulation within the gallery surfaces may have played critical rolls in lowering the catalytic activities.
B. EFFECT OF VARIOUS COMPATIBILIZERS IN POLYMER-CLAY NANOCOMPOSITES
Two types of common polymers (polyethylene, PE and polystyrene, PS) were used to develop various polymer-clay nanocomposites to study the effect of various compatibilizers on the properties of the resulting nanocomposites. Two different techniques have been chosen for the synthesis of these nanocomposites. Melt intercalation technique was used for all the samples containing PE and in-situ polymerization method was used to make nanocomposite samples containing PS. Five different compatibilizers with different polymeric structure and percent maleic anhydride (MA) were used to explore which factor will be more crucial in enhancing the resulting nanocomposite properties namely structural and thermal properties. The nanocomposites were characterized and compared using x-ray powder diffraction analysis (XRD), infra-red spectroscopy (FT-IR), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC).
Some of the compatibilizers did improve the extent of MMT exfoliation within the nanocomposites. In general, higher degree of exfoliation produce a significant enhancement in the nanocomposite properties (such as thermal properties). More significant thermal property enhancement occurred when compatibilizers with higher percentages of MA was utilized. However, the observation in this research indicates not a significant change in the nanocomposite thermal properties occur due to compatibilizer’s chemical structure.
|Commitee:||O'brien, Leah, Voss, Eric|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 54/06M(E), Masters Abstracts International|
|Subjects:||Physical chemistry, Materials science|
|Keywords:||Catalysis, Nanocomposites, Polymer, Surfactants, Triphase|
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