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

Effect of rate of pyrolysis on the textural properties of naturally-templated porous carbons from alginic acid

AbstractThe effect of pyrolysis rate on the properties of alginic acid-derived carbonaceous materials, termed Starbon®, was investigated. Thermal Gravimetry-IR was used to prepare porous carbons up to 800°C at several rates and highlighted increased CO2 production at higher pyrolysis rates. N2 porosimetry of the resultant carbons shows how pyrolysis rate affects both the mesopore structure and thus surface area and surface energy. Surface capacity of these carbons was analysed by methylene blue dye adsorption. In general, as the rate of pyrolysis increased, the mesopore content and adsorbent capacity decreased. It is considered here that the rapid production of volatiles at these higher rates causes structural collapse of the non-templated pore network. The work here demonstrates that pyrolysis rate is a key variable which needs to be controlled to maximise the textural properties of Starbon® required for adsorption applications

Recognition of Chiral Carboxylic Anions by Artificial Receptors

Many carboxylic molecules, ranging from drugs to flavors and fragrances, contain chiral centers. As a consequence, research has been carried out in order to design and synthesize artificial receptors for carboxylic anions. Many problems have to be solved for binding anions. The results obtained in the binding of carboxylic anions by guanidine, secondary ammonium and metal-center have been selected. The last part of this review focuses on chiral recognition of carboxylic anions by organic and metal-based chiral receptors

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

Trapping the oligomers: new promises in neurosciences

International audienc