title: Rheological study of chitosan acetate solutions containing chitin nanofibrils.
abstract: Rheological properties of chitosan acetate solutions containing chitin nanofibrils (n-chitin) and biocompatible plasticizers intended for preparation of biodegradable films are reported in the steady, oscillatory and transient shear flow. The experiments were performed on slurries with an optimum proportion of 65/35 wt.% between chitosan and n-chitin in the films which was determined from our results of mechanical properties and absorption of water vapor. The time-dependent dynamic experiments revealed the chitin nanofibrils as an effective "gelling agent" of chitosan phase. The phenomenon is explained by a chitosan-like surface of n-chitin and by the interactions inducing orientational cooperativity of chitosan molecules dissolved in close neighborhood of the anisotropic chitin nanofibrils. Additions of glycerol or poly(ethylene glycol), improving mechanical properties of the films, delay significantly the onset of gelation of chitosan/n-chitin slurries. The effect is induced by an increase in viscosity of the slurries and by their enhanced chaotropic character.
authors.affiliation: Institute of Macromolecular Chemistry AS CR, v. v. i., Heyrovského nám. 2, 162 06 Praha 6, Czech Republic. Electronic address: mikesova@imc.cas.cz.
authors.forename: Jana
authors.initials: J
authors.lastname: Mikešová
authors.affiliation: Institute of Macromolecular Chemistry AS CR, v. v. i., Heyrovského nám. 2, 162 06 Praha 6, Czech Republic; Institute of Biotechnology AS CR, v.v.i., Vídeňská 1083, 142 20 Prague 4, Czech Republic.
authors.forename: Jindřich
authors.initials: J
authors.lastname: Hašek
authors.affiliation: Institute of Macromolecular Chemistry AS CR, v. v. i., Heyrovského nám. 2, 162 06 Praha 6, Czech Republic.
authors.forename: Galina
authors.initials: G
authors.lastname: Tishchenko
authors.affiliation: Mavi Sud Srl, Viale Industria 1, 04011 Aprilia, Italy.
authors.forename: Pierfrancesco
authors.initials: P
authors.lastname: Morganti
mesh_terms: D000085:Acetates / Q000737:chemistry; D002686:Chitin / Q000737:chemistry*; D048271:Chitosan / Q000737:chemistry*; D005782:Gels; D005990:Glycerol / Q000737:chemistry; D049329:Nanostructures / Q000737:chemistry*; D010968:Plasticizers / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D012212:Rheology / Q000379:methods; D013227:Steam; D014783:Viscosity
chemical_list: D000085:Acetates; D005782:Gels; D010968:Plasticizers; D013227:Steam; D002686:Chitin; D011092:Polyethylene Glycols; D048271:Chitosan; D005990:Glycerol
keywords: Chitin nanofibrils; Chitosan solutions; Rheology