Behaviour of Amphiphilic Polysaccharides in Aqueous Medium

This paper describes the rheological and thermal behaviour of alkylated chitosan and hyaluronan derivatives and methylcellulose, Their behaviour is characterized by the formation of hydrophobic domains which may be considered as crosslinked points. Then, depending on the thermodynamic conditions (temperature, salt concentration), an aqueous solution transforms to a 3D-physical network formed on the basis of hydrophobic cooperative interactions. Key Words: Alkylated chitosan, alkylated hyaluronan, amphiphilic polysaccharides, methylcellulose, rheological behaviour. RESUMEN Este trabajo describe el comportamiento reológico y térmico de quitosano y hialuronano alquilados y de metilcelulosa. Dicho comportamiento está caracterizado por la formación de dominios hidrofóbicos que pueden considerarse como puntos de entrecruzamiento. Por tanto, en dependencia de las condiciones termodinámicas (temperatura, salinidad), las disoluciones acuosas pueden transformarse en una red física tridimensional basada en interacciones cooperativas de carácter hidrofóbico. Palabras Clave: Quitosano alquilado, hialuronano alquilado, polisacáridos anfifílicos, metilcelulosa, comportamiento reológico. n this paper, different amphiphilic polysaccharides based on chitin, cellulose and hyaluronan are described and few of their properties are given. First, chitin is a poly (β(1-4)-N-acetyl-D-glucosamine); it is a natural polysaccharide of major importance, first identified in 1884 (Figure 1a). This biopolymer is synthesized by an enormous number of living organisms (schrimps, crabs…).1 As many polysaccharides, chitin has some hydrophobicity and in aqueous NaOH it can form a lower critical solution temperature (LCST) solution with a critical temperature around 30°C.2 This characteristic temperature is very important to characterize the influence of temperature on the behaviour of a polymer in solution: at a temperature lower than the LCST, the polymer is soluble and one gets one phase; over the LCST, two phases