کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5190811 | 1381218 | 2006 | 8 صفحه PDF | دانلود رایگان |
This paper concerns the preparation of new water-soluble alkylated derivatives of hyaluronan (HA); these derivatives were synthesized under mild aqueous and well controlled conditions. The first step was to prepare a HA derivative selectively modified with adipic dihydrazide (HA-ADH) with a substitution degree of 0.08; then, alkyl chains with different chain lengths were introduced with a substitution degree around 0.05. These polymers being still water-soluble exhibit associating properties in the presence of external salt. Formation of hydrophobic domains is demonstrated from fluorescence measurements in the presence of pyrene as a probe. Then, it is shown that the viscosity of polymer solutions in 0.1Â M NaCl becomes non-Newtonian for HA grafted with C-10 and C-12 chains and increases rapidly with the polymer concentration over 1Â g/L. When the polymer concentration increases, a gel-like behaviour was observed from rheological measurements with the Gâ² modulus larger than Gâ³ in all the frequency range covered. The dependence of the shear stress on shear rate applied according to a continuous linear ramp provided evidence of the deformation or rupture of aggregates. The latter were shown to reform slowly. At the end, the influence of temperature was examined: first a slight increase in the modulus was observed followed by a decrease corresponding to reinforcement of the hydrophobic interactions.
Journal: Polymer - Volume 47, Issue 8, 5 April 2006, Pages 2706-2713