Measuring and Using the dn/dc of HPC Polymer and Microgel Solutions

Document Type

Conference Proceeding

Publication Date


Publication Title

APS March Meeting


The specific refractive index increment (dn/dc), the change in index of refraction with concentration, is essential for static light scattering (SLS) experiments on polymer solutions. With a reliable value for dn/dc, SLS yields basic polymer properties such as radius of gyration, molecular weight, and second virial coefficient. This study focuses on determining dn/dc values of hydroxypropylcellulose (HPC) polymer and microgel solutions and practically applying these values in SLS. Using a differential refractometer, HPC solutions were analyzed at a range of concentrations, molecular weights, wavelengths, temperatures, and filtration protocols. It was determined that dn/dc of HPC polymer is independent of temperature in good solvents, slightly dependent on molecular weight, inversely proportional to wavelength squared, and sensitive to polymer solution's filtration protocol. HPC microgel testing produced dn/dc values one order of magnitude larger than those of HPC polymer solutions and did not support the expected wavelength dependence. These findings were analyzed and used to obtain a molecular weight, radius of gyration, and second virial coefficient for HPC polymer and microgel solutions.