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.

pH-responsive hydrogel membranes based on modified chitosan: water transport and kinetics of swelling

“…In most published reports on the hydrogel swelling, values of n close to 0.5 or over 0.5 are presented. Only a few papers report values of n<0.5 [25,[43][44][45][46][47].…”

Controlled release effervescent buccal discs of buspirone hydrochloride:in vitroandin vivoevaluation studies

“…Variety of dosage forms like tablets (Boyapally et al, 2010, Kanjanabat & Pongjanyakul, 2011, discs (Yehia et al, 2008;Jaipal et al, 2013), patches (Abu-Huwaij et al, 2011;Kaur & Kaur, 2012;Govindasamy et al, 2013) and gels (Das et al, 2012;Bueno et al, 2013) have been reported in the literature for buccal delivery of drugs. Buccal discs are flat, thin solid unit non-flexible compacts; and are similar to buccal tablets.…”

Introduction of Microbial Biopolymers in Soil Treatment for Future Environmentally-Friendly and Sustainable Geotechnical Engineering

“…When soils have increasing amounts of water, dehydrated biopolymer gels (Figure 6a,b) or biopolymer-clay matrices (Figure 6c,d) will adsorb and transfer water to hydrogels with a resulting volumetric expansion (i.e., swelling) [111,112]. The elastic properties of biopolymer hydrogels, such as their tensile strength and stiffness, diminish exponentially with increased water content [113], resulting in a remarkable reduction in soil strength, to approximately 1/10th of the strength of the dried state in a fully saturated condition.…”