title: Transient and quasi-permanent networks in xyloglucan solutions.
abstract: Viscoelastic properties of aqueous solutions of xyloglucan extracted from Hymenaea courbaril seeds (Jatobá gum) were investigated by rheology over a wide range of concentrations and temperatures. The polymer was characterized in dilute solutions by light scattering measurements and size exclusion chromatography. Xyloglucan formed, in semi-dilute solutions (C 0.3 wt%), a transient network with cross-links characterized by a broad distribution of lifetimes, independent of the temperature and concentration. Progressively, at higher temperatures (>60°C), a second much weaker quasi-permanent network was formed and attributed to the exchange of intra- to inter-chain bonds. The stiffness of the second network increased with decreasing temperature, but it could be easily broken by applying a relatively weak shear stress and is readily reversible on re-heating, and partially reversible on resting at 20°C.
authors.affiliation: LUNAM Université, Université du Maine, CNRS UMR 6283, IMMM, Avenue Olivier Messiaen, 72085 LE MANS Cedex 9, France; BioPol, Chemistry Department, Federal University of Paraná, 81531-980 Curitiba, PR, Brazil. Electronic address: rilton@ufpr.br.
authors.forename: Rilton Alves
authors.initials: RA
authors.lastname: de Freitas
authors.affiliation: BioPol, Chemistry Department, Federal University of Paraná, 81531-980 Curitiba, PR, Brazil.
authors.forename: Vivian C
authors.initials: VC
authors.lastname: Spier
authors.affiliation: BioPol, Chemistry Department, Federal University of Paraná, 81531-980 Curitiba, PR, Brazil.
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Sierakowski
authors.affiliation: LUNAM Université, Université du Maine, CNRS UMR 6283, IMMM, Avenue Olivier Messiaen, 72085 LE MANS Cedex 9, France.
authors.forename: Taco
authors.initials: T
authors.lastname: Nicolai
authors.affiliation: LUNAM Université, Université du Maine, CNRS UMR 6283, IMMM, Avenue Olivier Messiaen, 72085 LE MANS Cedex 9, France.
authors.forename: Lazhar
authors.initials: L
authors.lastname: Benyahia
authors.affiliation: LUNAM Université, Université du Maine, CNRS UMR 6283, IMMM, Avenue Olivier Messiaen, 72085 LE MANS Cedex 9, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Chassenieux
mesh_terms: D002236:Carbohydrate Conformation; D005936:Glucans / Q000737:chemistry*; D052597:Hymenaea / Q000737:chemistry*; D009844:Oligosaccharides / Q000737:chemistry; D012996:Solutions; D014783:Viscosity; D014990:Xylans / Q000737:chemistry*
chemical_list: D005936:Glucans; D009844:Oligosaccharides; D012996:Solutions; D014990:Xylans; C029353:xyloglucan
keywords: Gel; Transient network; Viscosity; Xyloglucan