Synthesis and Characterization of Potassium Dihydrogen Phosphate (KDP) Nanocomposites.

Potassium Dihydrogen Phosphate (KDP) nanocrystals were synthesized in micellar solutions of block copolymers of polystyrene (PS) and poly(ethylene oxide) (PEO) in toluene/Dimethoxyethane solvent. The synthetic procedure entailed the doping of the block copolymer solutions with phosphoric acid and the stochiometric neutralization of the aciddoped system with potassium hydroxide (KOH). The neutralization reaction was localized within the core of the micelle which in effect served as a hanoreactor or nanovessel for the reaction. Micellization of the block copolymer molecules was induced upon doping the solution with phosphoric acid which resulted in ion dipole binding of the protons to the ethylene oxide molecules in the core of the micelle. The polystyrene segments of the copolymer surround the micelle core as a corona. Dynamic and static light scattering and solution viscometry were used to elucidate the micellization process and the extent of aggregation (micelle size) in the block copolymer solutions doped with phosphoric acid. Light scattering results indicated that acid doping, at levels of 20 mole% or higher, based on the concentration of ethylene oxide residues, induced complete micellization of copolymer molecules. The acid-doped micellar solutions were neutralized with the KOH to form colloidal solutions in which K+H2P04~ ions were ostensibly bound within the PEO core of the micelle. These neutralized colloidal solutions were precursors for the nanocrystallization of KDP. Solutions were puddle cast on glass slides and dried at -50C to yield films that were subsequently annealed to promote crystallization of KDP. Differential scanning calorimetry (DSC) and atomic force microscopy (AFM), respectively, were used to study the xn crystallization of KDP and the morphology of thin films spin coated from the micellar solutions. The objective of this thesis was to synthesize an ordered array of KDP nanocrystals within the block copolymer film. DSC scans on the annealed films in some cases showed the presence of crystalline KDP in the composite film. AFM micrographs also showed the formation of nanosized particles of KDP. However, these nanocrystals were polydisperse in sizes and were randomly distributed. The random distribution and polydispersity indicated the crystallization of KDP material was not confined within the core of micelle