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|Title:||Wet Adhesion of Polyvinylamine-Phenylboronic Acid to Cellulose Hydrogel|
|Advisor:||Pelton, Robert H.|
|Keywords:||wet adhesion, acid, cellulose, hydrogel, boronic, polymers|
|Abstract:||<p> The ability of a never-dried paper web on a paper machine to resist breakage is commonly referred to as paper wet-web strength. Low wet-web strength can lead to frequent breaks which interrupt production and lower paper machine efficiency. Currently, no commercial products provide the function of enhancing wet-web strength. Boronic acid derivatized polyvinylamine (PVAm-PBA) showed high instantaneous wet adhesion to regenerated cellulose membranes. The objective of the research summarized in this thesis was to determine the factors and mechanisms dictating PVAm-PBA adhesion to wet cellulose. In addition, narrowly distributed PVAm microgel was prepared and the wet adhesion of boronate-microgels to cellulose is reported.</p> <p> The phase behavior and surface tension of PVAm-PBA were measured as functions of pH and the degree of PBA substitution. The pH ranges over which phase separation occurred increased with PBA substitution. 150 kDa PVAm-PBA with 4% derivatization phased separated at pH 8.5 to 9.5.The copolymer based on 51 % substitution was insoluble over most of the pH range. The hydrophobicity of copolymers was reflected in the significant lowering of surface tension particularly at high pH. Additionally, fructose, which binds to borate, influenced the titration curves but did not influence surface tension.</p> <p> Pairs of wet, regenerated cellulose films were laminated with PVAm-PBA and the forces required to delaminate the never-dried laminates, were measured as functions of adhesive structure and application conditions. The greatest wet adhesion was obtained with 150 kDa PVAm with 16% of the amines bearing phenylboronic moieties. The pH at which the PVAm-PBA was adsorbed onto the cellulose was the dominant process parameter. The specific role of the phenyl boronic groups was illustrated in two ways: a) replacing the B(OH)2 with OH (i.e. phenol) gave much lower adhesion; and, b) wet adhesion was greatly reduced by the presence of sorbitol which effectively competes with cellulose for boronate binding sites.</p> <p> The interaction of boronate and cellulose was studied. Owing to poor solubility of cellulose, two model polymers: dextran and hydroxyethyl cellulose (HEC) and two saccharides: glucose and cellobiose were measured by boron NMR measurement, tensile extension, fluorescence spectra, viscometer and peeling test methods. In conclusion, carbon-1, 2 diols at one end of cellulose chain can react with boronic acid. By contrast, carbon-2, 3 diols, which are abundant on cellulose chains, cannot react with boronic acid and the other diols, such as carbon-3, 4 diols and carbon-4, 6 diols cannot react with boronic acid. The high adhesion of boronate containing polymers to cellulose membranes was attributed to boronate ester formation with the cellulose end groups on the membrane surfaces. </p> <p> Finally, a simple and effective methodology was demonstrated for the preparation of polyvinylamine microgel with a narrow distribution. Boronate derivatives of PVAm microgels displayed very high wet adhesion to cellulose over a broad pH range.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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