title: Synthesis and swelling behavior of xanthan-based hydrogels.
abstract: In this work xanthan chains were crosslinked by esterification reaction at 165 °C either in the absence or in the presence of citric acid. Higher crosslinking density was obtained using citric acid, as evidenced by its lower swelling degree. Tensiometry, a very precise and sensitive technique, was applied to study swelling rates and diffusion mechanisms of water, which was initially quasi-Fickian, controlled by wicking properties, changing to Fickian or Anomalous, depending on hydrogel composition. Hydrogels swelling degree increased at high pH values, due to electrostatic repulsion and ester linkages rupture. Equilibrium swelling degree was affected by salts, depending on gel composition and kind of salt. Effects could be explained by interaction between ions and polymeric chains, EPA/EPD ability of water or osmotic gradient.
authors: Instituto de Química, Universidade de São Paulo, P.O. Box 26077, São Paulo, SP 05513-970, Brazil.
authors: Vania Blasques
authors: VB
authors: Bueno
authors: Ricardo
authors: R
authors: Bentini
authors: Luiz Henrique
authors: LH
authors: Catalani
authors: Denise Freitas Siqueira
authors: DF
authors: Petri
mesh_terms: D060326:Chemistry Techniques, Synthetic; D019343:Citric Acid / Q000737:chemistry; D004058:Diffusion; D020100:Hydrogels / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D011135:Polysaccharides, Bacterial / Q000138:chemical synthesis* / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D020100:Hydrogels; D011135:Polysaccharides, Bacterial; D014867:Water; D019343:Citric Acid; C002563:xanthan gum