Gelation of steroid-bearing dextrans by surfactants

摘要: Gelation of hydropho-bically modified dextrans, prepared by covalent attachment deoxy-cholic acid (DCA) to dextran (Dex), with several surfactant categories was investigated viscosity and rheological techniques. Freshly Dex—DCA solutions do not gel over a large range polymer concentration for any categories, anionic, cationic, nonionic, zwitterionic, as indicated only minor change in the solution’s apparent (capillary viscometers). For 1% (w/w) at intermediate sodium deoxycholate concentrations (0.008–0.03 M) stiff macroscopic transparent is formed when samples mature more than 10 days room temperature (independently sonication during preparation). The time required formation varies shows minimum around about mM DCA increases up 30 near phase boundaries. Continuous-flow measurements were carried out Dex-DCA/DCA mixture. indicate high yield stress but an easy breakdown into small particles stressed. extrapolated zero-shear transition from fluid solution 33 °C (heat scan) opposite gelation 20 (cool scan). In these gelation—fluidization cycles recovers practically its initial mechanic properties.