Aspects of amidization of chitosan

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dc.contributor.authorToffey, Ackahen
dc.contributor.committeechairGlasser, Wolfgang G.en
dc.contributor.committeememberFrazier, Charles F.en
dc.contributor.committeememberHelm, Richard F.en
dc.contributor.committeememberYoungs, Robert L.en
dc.contributor.committeememberWightman, James P.en
dc.contributor.departmentWood Science and Forest Productsen
dc.date.accessioned2014-03-14T21:11:56Zen
dc.date.adate2008-06-06en
dc.date.available2014-03-14T21:11:56Zen
dc.date.issued1996en
dc.date.rdate2008-06-06en
dc.date.sdate2008-06-06en
dc.description.abstractThe intent of this research was to develop an understanding of an amidized chitosan-from-chitosan regeneration process discovered in our laboratory. In this study several characterization methods including DMTA, TMA, TGA, X-ray diffraction, FTIR, solid state CP-MAS ¹³C NMR, and HPLC were used to study the transformation of various ionic complexes of chitosan (N-acylate) to their respective N-acyl homologs of chitosan; and several properties of these materials were examined. DMTA and TMA provided information on changes in T<sub>g</sub> as well as modulus-changes and glass formation underlying the transformation of the N-acylate to the N-acyl derivative. X-ray diffraction and FTIR shed some insights on the morphology of the N-acetyl homolog of chitosan in relation to native chitin. Solid state CP-MAS ¹³C NMR provided evidence of the conversion of N-acylate to N-acetyl. Enzymatic hydrolysis of native chitin and amidized chitosan homologs and subsequent identification of fractions by HPLC allowed a comparison of various amidized chitosan homologs in terms of their recognition and degradation by chitinolytic enzymes. Solid state CP-MAS ¹³C showed that the heat treatment of the ionic complex of chitosan results in thermal dehydration leading to the formation of the N-acetyl group at the C-2 of chitin. The DS of amidized chitosan varied between 0.1 and 0.6. T<sub>g</sub>-changes with time and heating temperature were used as a variable to monitor amidization. Kinetics analysis indicated that the amidization of various ionic complexes of chitosan is a first order, two-phase process with activation energies of 14±1 kcal/mol and 21±2 kcal/mol for the first and second phase, respectively. These values did not vary with the type of acid used in the formation of the chitosan complex. This two-phase behavior is explained with the influence of vitrification on chain mobility. In situ DMTA was found to be a suitable technique for monitoring the phase transformation of chitosonium acetate and chitosonium propionate from a rubbery to a glassy phase (vitrification). Consequently, the concept of TTT-cure diagram analysis was used to describe such phase changes and map out vitrification and full cure curves. As in thermosets, the vitrification curve describing glass formation in these materials is S-shaped. The time to full cure decreased with increasing heating temperature. The activation energy for vitrification is the same irrespective of the type of acid used in the preparation of chitosan complex. Thermal analysis revealed that the T<sub>g</sub> of N-acyl homologs of chitin displays a stepwise relationship with length of N-acyl substituent. These materials are characterized by two transitions designated as β- and α-relaxation. Additionally, enzymatic hydrolysis of N-acyl homologs of chitosan using an enzyme mixture of chitinase, chitosanase, and β-N-acetylglucosaminidase and subsequent identification of fractions revealed that these enzymes recognize and degrade chitin irrespective of the N-acyl substituent at the C-2 position of chitin at any DS.en
dc.description.degreePh. D.en
dc.format.extentxix, 214 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-06062008-144850en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06062008-144850/en
dc.identifier.urihttp://hdl.handle.net/10919/37955en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V856_1996.T644.pdfen
dc.relation.isformatofOCLC# 36114035en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectamidizationen
dc.subjectimidizationen
dc.subjectvitrificationen
dc.subjectglass transitionen
dc.subjectchitinen
dc.subjectchitosanen
dc.subject.lccLD5655.V856 1996.T644en
dc.titleAspects of amidization of chitosanen
dc.typeDissertationen
dc.type.dcmitypeTexten
thesis.degree.disciplineWood Science and Forest Productsen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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