| Popis: |
The micellar properties of the ABA poly(oxyethylene)-poly(oxypropylene) block copolymer Pluronic F127 have been examined in water and electrolyte solution by photon correlation spectroscopy, total intensity light scattering and viscometric techniques. The hydrodynamic micellar radius in water, as calculated from diffusion data at the critical micelle concentration, remained constant at 10.2 ± 0.1 nm, over the temperature range 35–45 °C. Viscometric studies, however, showed a progressive dehydration of the micelles with temperature increase and it is clear from total intensity light scattering that this dehydration is accompanied by a concomitant increase in anhydrous volume such that the overall hydrated volume is unaffected by temperature change. Increase of solution concentration above about 10 g · dl−1 over this temperature range caused a marked increase of mean micellar size and of the polydispersity of micellar sizes, indicative of the onset of gelation. The influence of temperature on micellar size and hydration was less pronounced in the presence of 0.5 mol-dm−3 sodium chloride and gelation commenced at higher solution concentrations. The relevance of these studies to the thermal gelation of this poloxamer is discussed. |
