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Chitosan may be chemically modified by reductive amination leading to the grafting of hydrophobic alkyl chains along the hydrophilic macromolecular chain. This allows to obtain amphiphilic polymers whose the hydrophobicity (or the hydrophile-lipophile balance, HLB) may be adjusted according to the length of the grafted alkyl chain or the degree of substitution of the amine functions. The existence...
In this paper, from many new examples, our approach on the preparation of chitins and chitosans with controlled physico-chemical characteristics was presented. The chitosan samples were prepared from α-chitin from crustacean shells and β-chitin from squid pens. The chitin deacetylation was carried out according to two methods using, respectively, as alkaline agent, the aqueous sodium hydroxide solution...
The complexation of copper ions by chitosan and its oligomers is investigated using potentiometric and spectrophotometric methods to study the nature of the complexes involved and the role of the degree of polymerisation. Two complexes are demonstrated. Their structure is proposed, the pH range in which they are respectively stable is determined and their stability constants calculated. Finally a...
The use of infrared spectroscopy for characterization of the composition of chitin and chitosan covering the entire range of degree of acetylation (DA) and a wide variety of raw materials is examined further. The ratio of absorbance bands selected was calibrated using 1 H liquid and 13 C CP-MAS solid-state NMR as absolute techniques. IR spectra of the structural units of these...
Methylcellulose is a natural polymer which gels on heating. This gelation is thermoreversible and attributed to hydrophobic interactions. Its mechanism is not well understood but the presence of hydrophobic zones is needed to initiate the physical crosslinking. Dynamic mechanical experiments performed in a large frequency range are presented and allow discussions for improving our understanding of...
Chitin was extracted from squid pens and the used conditions allow to obtain a completely N-acetylated β-chitin with a molecular weight large enough for the obtention of chitosans of high molecular weight. Deacetylation, leading to the obtention of chitosan, was performed according to two processes (Kurita and Broussignac conditions) and the physicochemical characteristics (degree of acetylation and...
This paper is devoted to the rheological properties of cationic cellulosic fibres with different degrees of substitution and swelling. Depending on the concentration of the fibre suspension, the system behaves as a solution (C<5g/l) or as a gel. The rheological characteristics of the suspensions are directly related to the degree of substitution, the degree of swelling and the degree of fibrillation...
This article concerns the protonation of chitosan in acetic acid aqueous solution with variable concentration. Comparison with HCl is also drawn. Potentiometry allows the determination of the degree of protonation and the pK0. Conductimetry and viscometry are combined to follow the role of protonation on solubilization of chitosan. Solubilization occurs for a degree of protonation around 0.5 as previously...
Methylcelluloses are widely used for industrial purposes due to their peculiar properties. These are the consequence of associative behaviour due to hydrophobic interactions involving highly substituted units. The properties of commercial samples with heterogeneous distribution of the substituents and laboratory-made samples, with a more homogeneous distribution, are compared to allow a better understanding...
In order to obtain thermoplastic starch-based materials with a reinforced hydrophobicity, amylose and amylopectin were acetylated following the pyridine-acetic anhydride procedure. An amylose-rich starch triacetate was saponified under controlled conditions to obtain products with different acetyl contents. The adsorption of water by these polymers equilibrated in a 98% r.h. atmosphere was studied...
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