title: Physicochemical behaviour of chitin gels.
abstract: Syneresis of chitin gels formed in the course of N-acetylation of chitosan in hydroalcoholic media has been studied. A critical cross-linking density related to a critical acetylation degree for which the gel undergoes weak syneresis and swells in water was shown (degree of acetylation (DA) 88%). Above this value, the weight loss during syneresis increases with DA. Conversely, syneresis decreases on increasing the polymer concentration, but disappears at a macroscopic level for a polymer concentration close to the critical concentration of entanglement in the initial solution. An increase in temperature favours the formation of hydrophobic interactions and new inter- and intramolecular hydrogen bondings. Due to the weak polyelectrolyte character of chitin, the weight of the gel depends on the pH and ionic strength of the media. Swelling-deswelling experiments show that the swelling of the gel is not fully reversible in relation with the formation of new cross-links during the depletion of the network. Our results reveals that the balance between segment-segment and segment-solvent interactions as well as the molecular mobility play the major role.
authors.affiliation: Laboratoire des Matériaux Polymères et des Biomatériaux (UMR CNRS 5627), Université Claude Bernard, Villeurbanne, France.
authors.forename: L
authors.initials: L
authors.lastname: Vachoud
authors.forename: N
authors.initials: N
authors.lastname: Zydowicz
authors.forename: A
authors.initials: A
authors.lastname: Domard
mesh_terms: D000107:Acetylation; D000438:Alcohols / Q000737:chemistry; D002686:Chitin / Q000737:chemistry*; D005782:Gels; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D011108:Polymers / Q000737:chemistry*; D011189:Potassium Chloride / Q000737:chemistry; D013696:Temperature
chemical_list: D000438:Alcohols; D005782:Gels; D011108:Polymers; D002686:Chitin; D011189:Potassium Chloride