Cellulose is one of the most abundant natural macromolecule and commercially available in a variety of forms. One of the most significant markets concerns carboxymethyl cellulose (CMC) because of its widespread application as a biomaterial and in industrial processes. As a consequence, CMCs are studied for a long time by a selection of techniques. Associated to applications in medicine, pharmacy, biology, and particularly as components of biomaterials, its fundamental properties on a molecular scale are of high importance. However, CMCs are known for their dispersity, which may impose problems for a more fundamental molecular characterization.
We approach this characterization challenge by two seminal macromolecular characterization techniques in solution. These techniques comprise molecular hydrodynamic analysis via viscometry and sedimentation analysis in analytical ultracentrifugation (AUC) as well as size exclusion chromatography (SEC) coupled to multi-angle laser light scattering (MALLS). We do this over a wide range of molar masses and desired degrees of dilution.
We start our approach with the determination of intrinsic viscosities followed by the calculation of the degree of dilution. In the following, we perform sedimentation velocity experiments via AUC. Here, we could verify the range of concentrations suitable for sedimentation velocity experiments to perform the extrapolation to infinite dilution, aiming at reconciliation of the molecular hydrodynamic properties. Consequently, molar masses are determined by SEC-MALLS.
All of the hydrodynamic parameters of a particular CMC sample – intrinsic viscosity, intrinsic sedimentation coefficient, molar masses / diffusion coefficients – are subsequently shown to interrelate via a hydrodynamic invariant concept that demonstrates the quantitative nature of our approach. This quantitative nature is further underpinned by physical interrelation of scaling relationships. Our approach provides an opportunity for a comprehensive characterization of biomaterials in solution even at very high degrees of dispersity. This includes valuable information to establish quantitative structure-property relationships of biomaterials.