| Abstract
| - Dynamic and static light scattering experiments were performed on 0.1 M NaCl aqueoussolutions of semirigid hyaluronan and rigid xanthan in the dilute and semidilute regime. In the diluteregime, typical good solvent behavior is found, and the intrinsic persistence length of hyaluronan (≈100Å) and xanthan (≈1000 Å) is determined. However, in the semidilute regime the time autocorrelationfunction of the scattered electric field is found to be bimodal for hyaluronan and xanthan solutions. Theshort time relaxation has a typical q-2 dependence and is attributed to the relaxation of concentrationfluctuations characterized by a cooperative diffusion mechanism. The long time relaxation has a q-3dependence, characteristic of intraparticle dynamics. This behavior is not consistent with predictedsemidilute, good solvent system behavior but instead indicates the presence of associations or microgels.The corresponding slow relaxation times appear to be related to the macroscopic viscosity of thesurrounding polymer solution. The effect of the molecular weight and polymer concentration wasinvestigated.
|
