Preparation and characterization of poly (4- Vinyl Pyridine) grafted chitin beads

ABSTRACT: The subject of this thesis is the preparation and characterization of chitin gel beads by thermoreversible gelation, which followed by nonsolvent addition, and via chemical modification followed by non-solvent addition. Physical properties of the chitin gels obtained by nonsolvent addition and by heating to the gelation point followed by nonsolvent addition were investigated. The effects of the type and composition of the solvent system on the gelation time, gelation temperature, swelling ratio and the Young’s modulus were studied. Another aspect of this study was to exploit the gel formation capability of chitin to form modified gel beads based on the polymer. To fulfill this aim, a new combined approach was taken to carry out redox initiated grafting under homogeneous conditions followed by nonsolvent addition to prepare poly(4-vinyl pyridine) (P4VP) grafted chitin gel beads. Grafting percentages up to 226% were obtained. The grafted and nongrafted products were characterized by FTIR spectrophotometry, XRD and SEM analyses and by TGA. The swelling behaviour of the beads was studied in aqueous solution in neutral, acid and phosphate buffers. XRD analysis showed that the characterized product had a lower crystallinity when compared to the pure chitin. Thermal analysis carried out by TGA revealed that the products were less stable against thermal treatment than chitin. While chitin had a weight loss of 75 % at 500ºC the grafted product showed 90 % weight loss. The maximum decomposition temperature for chitin was 380ºC, but for the grafted products this value was as low as 305ºC. The DSC analysis of the chitin and the grafted chitin confirmed less heat stability of chitin-g-P4VP. The potential of the gel beads for wastewater treatment applications was tested by studying their heavy metal and fat binding properties. The P4VP grafted and nongrafted gel beads were tested for their cholesterol and Fe3+ adsorption capacities. The beads derived from chitin-g-P4VP were found to have higher adsorption capacities than chitin beads due to a microporous bead surface and chemical modification. The quaternized chitin-g-P4VP gel bead proved to be a potential Hg2+ adsorbent. …………………………………………………………………………………………………………………………………………………………………………………………………………