Dilute Solution Viscometry is one of the oldest but most informative techniques of polymer characterization. Solution viscometry reveals invaluable information on molecular density, conformation and structure (i.e. branching, chain length, chain flexibility and aggregation) of macromolecules in solution. Solution viscosity can also be used to determine the molecular weights of polymers. Intrinsic Viscosity, , a solution viscosity parameter, relates directly to the molecular mass of macromolecules in solution by the Mark-Houwink-Sakurada (M-H-S) equation:
Viscosity detectors can be used online coupled with a GPC/SEC setup to determine molecular density and conformation (i.e. Hydrodynamic Volume) and therefore can be used to generate Universal Calibration Curve. The Universal Calibration Principle is independent of the standard type and provides the TRUE molecular weight of polymers.
This technique is a perfect substitute for light scattering when the sample possesses fluorescence properties in solution, has a low Refractive Index Increment (dn/dc) or has molecular weight below the lower limit for light scattering measurement.
Using Einstein’s viscosity equation, solution viscometry can also determine the hydrodynamic size of macromolecules in solutions: