title: What is the real value of chitosan's surface energy?
abstract: Because of conflicting reports and unrealistic literature values, a systematic study of the surface energy of chitin, chitosan, and their respective monomeric counterparts was carried out using contact angle measurements on films and pellets, before and after different purification procedures. All the commercial samples of these polymers were shown to contain nonpolar impurities that gave rise to enormous errors in the determination of the polar component of their surface energy. After their thorough removal, the value of the total surface energy (gamma(s)), and particularly of its polar component, increased considerably and reached the classical polysaccharide figures of gamma(s)d approximately 30 and gamma(s)p approximately 30 mJ/m2. The characterization of the impurities by gas chromatography/mass spectrometry analysis indicated the presence of significant amounts of higher alkanes, fatty acids, and alcohols and sterols.
authors.affiliation: CICECO and Department of Chemistry, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal. gcunha@ua.pt
authors.forename: Ana G
authors.initials: AG
authors.lastname: Cunha
authors.forename: Susana C M
authors.initials: SC
authors.lastname: Fernandes
authors.forename: Carmen S R
authors.initials: CS
authors.lastname: Freire
authors.forename: Armando J D
authors.initials: AJ
authors.lastname: Silvestre
authors.forename: Carlos
authors.initials: C
authors.lastname: Pascoal Neto
authors.forename: Alessandro
authors.initials: A
authors.lastname: Gandini
mesh_terms: D048271:Chitosan / Q000032:analysis* / Q000737:chemistry*; D004734:Energy Metabolism; D013499:Surface Properties
chemical_list: D048271:Chitosan