title: Effect of changes in relative humidity and temperature on ultrathin chitosan films.
abstract: We have prepared uniform films of chitosan with thicknesses 20 nm < h < 200 nm by spincoating solutions of chitosan dissolved in dilute acetic acid onto silicon substrates while controlling the spin speed and the relative humidity inside the spincoater. After neutralizing the films, they readily absorbed water in the presence of high humidity. Heating of the films to elevated temperatures caused a large irreversible decrease in the film thickness, a small increase in the index of refraction, and a reduction in water absorption, as measured using ellipsometry. Comparisons of infrared absorption measurements of chitosan films collected before and after heating indicate an increase in the degree of acetylation with heating. Collectively, these observations are consistent with the release of bound water and a chemical change similar to acetylation at elevated temperatures.
authors.affiliation: Department of Physics, Guelph-Waterloo Physics Institute, and Centre for Food and Soft Materials Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Murray
authors.forename: John R
authors.initials: JR
authors.lastname: Dutcher
mesh_terms: D048271:Chitosan / Q000737:chemistry*; D020099:Coated Materials, Biocompatible; D006813:Humidity; D008968:Molecular Conformation; D008970:Molecular Weight; D013696:Temperature; D013816:Thermodynamics
chemical_list: D020099:Coated Materials, Biocompatible; D048271:Chitosan