Nitrogen sorption as a tool for the characterisation of polysaccharide aerogels

Supercritically dried aerogels of several polysaccharides (chitin, chitosan, alginate, alginic acid, k- carrageenan, and agar) have been characterised by physisorption ofN2. Surface areas as high as 570m2 g−1 have been measured. The nature of the functional groups of the polysaccharide significantly influences the adsorption of N2 on the surface of the aerogel. The net enthalpy of adsorption increases with the polarity of the surface groups of the polymer, in the order chitin < agar≤chitosan < carrageenan < alginic acid∼alginate. The surface area and the mesopore distribution of the aerogels depend both on the dispersion of the parent hydrogel and on the behaviour of each polymer in the drying treatment. Aerogels which retain the dispersion of the parent hydrogel are mainly macroporous (pores larger than 50 nm) while materials liable to shrink upon solvent exchange form mesoporous structures

La chimie organométallique du cobalt (Application à la reconnaissance moléculaire d'anions biologiques et d'alcools secondaires)

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Marine Polysaccharides and their Conversion into Functional Materials

International audienceNatural polysaccharides are supports for sensors, absorbents and catalysts. They are also gelling agents in the aqueous phase, due to the high level of dispersion of hydrocolloids. This article focuses on an effective method to prepare dry materials which retain the dispersion of the polymer hydrogel, namely polysaccharide aerogels. The diverse surface functionalities like hydroxy, carboxy or amino groups of the polysaccharide aerogels are accessible to catalysts and reactants and can be easily modified to tune the functionality of the materials

Synthesis and characterization of a small library of bisglucosides: Influence of the nature of the diol/diphenol used in O-glucosylation

International audienc

Natural materials with high surface area. Physisorption methods for the characterization of the texture and surface of polysaccharide aerogels

International audiencePolysaccharide hydrogels are open networks of naturally functionalized hydrocarbon materials. In this study, gels of several polysaccharides (alginate, alginic acid, j-carrageenan, agar, chitin and chitosan) have been prepared by various gelling methods. Supercritical drying allows to form aerogels with surface areas as high as 600 m2 g1 and active sites with acid (alginate or carrageenan) or basic (chitosan) properties, which confer them effective catalytic properties. The macroporous volume of polysaccharide aerogels can reach 40 cm3 g1 and provide an excellent accessibility of the active sites. Physisorption of N2 at 77 K has allowed to assess a secondary mesoporosity attributed to contacts between polymer fibrils. The enthalpies of physisorption have been analyzed through the BET method and the measurement of isosteric heat of adsorption of Ar. Comparison plots have been drawn on the basis of a reference isotherm exploiting the absence of microporosity of fumed silica and the absence of mesoporosity of Lichrospher. Deviations of the low-pressure part of the comparison plots have been exploited to evaluate a variation of density of the physisorbed monolayers in good correlation with enthalpies of adsorption. The molecular area of adsorbed N2 is an inverse function of the energetics of physisorption. The adsorption heat increases with the polarity of the polymer in the order of chiti