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Title: Structured porous materials of chitin and chitosan
Author: Lizardi-Mendoza, Jaime
ISNI:       0000 0001 3611 5035
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2007
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Chitin is an abundant polysaccharide that is mainly found in the exoskeleton of arthropods (insect, crustaceans, etc.). It is chemically and structurally similar to cellulose but chitin has an acetamido group in the second position: Chitosan, the main derivative ofchitin, is deacetylated leaving the amide groups uncovered and liable to be protonated in acid environments. These together with other features provide chitin and chitosan with a range of distinctive functional properties that including structural qualities, adsorption capacity, reactivity, biocompatibility, bioactivity and biodegradability. Such chitin and chitosan properties have been the origin of increasingly interest and oftheir application in diverse fields. In order to improve the availability ofthe functional groups ofchitin and chitosan in the solid stat~ it is proposed the generation ofporous materials with large surface area. The proposal is remove the liquid phase of chitin and chitosan physical gels using C02 critical point drying to minimize the disruption of the formed microstructure. The analysis of the diverse solution characteristics and their relationships with' the features ofthe gel and porous structures produced provide basic information that could allow the design offunction specific structures. Two types ofchitin solutions were obtained using dimethylacetamide containing 5% LiCI and cold «4°C) 10% NaOH as solvents. Chitosan was dissolved in diluted acetic acid and in formaldehyde sodium bisulfite (FSB) solution. Homogeneously deacetylated chitosan was obtained and dissolved in water. The basic characterisation ofthe solutions indicate that the molecular interaction ofthe polysaccharide with each solvent is distinctive. Every solution type were cast and physical gels were generated by diffusion of gelating agent fumes. Additionally, gels of alkali chitin (chitin in 10% NaOH) were produced by thermal treatment. Once washed, a portion of each type ofgel was equilibrated in water and other part in acetone; except the homogeneous chitosan gels that were equilibrated only in acetone. The water gels were freeze dried and the acetone was removed by C02 critical point drying to get porous materials. The porous structure of such materials were analyzed by scanning electron microscopy, crystallinity, chemical compositionand BET gas adsorption. The freeze dried materials have porous structure morphology similar to what has been previously reported. On the other hand, most ofthe critical point dried porous structures are in the mesoporous range and have large specific surface areas (323-887 m2/g). Apparently, for this tYpe ofmaterials the molecular interactions occurring in the solution could be related with the morphology of their respective porous structure
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available