Determination of the viscoelastic behavior of sodium hyaluronate in phosphate buffered saline with rheo-mechanical and rheo-optical methods

Abstract

Aqueous solutions of microbially produced sodium hyaluronate in phosphate buffered saline (pH=7.4, T=25 °C) were characterized with regard to their molecular parameters and viscoelastic behavior. The weight-average molar mass (MW), z-average radius of gyration (RG), and their distributions were determined using a hyphenated assembly of size exclusion chromatography, multi-angle light scattering, and a differential refractive index detector. Correlation of the obtained results with viscometric data enabled the establishment of [η]-M and RG-Mrelationships ([η]=0.034MW0.79; RG=0.039MW0.59). Viscoelastic behavior was investigated by steady state shear experiments. The viscosity yield was determined for varying concentrations and molar masses using shear rates from 10−3 to 103 s−1. The elastic behavior in shear flow, represented by the first normal stress difference N1, has been detected on one hand via rheo-mechanical experiments and on the other hand being correlated from the rheo-optical material functions flow birefringence Δn′ and its orientation ϕ utilizing the stress-optical rule. This correlation enabled the extension of the measurement range toward lower absolute values of N1 of more than two decades. The correlated values were in good agreement with the data obtained by rheo-mechanical measurements.