Measuring dn/dc for Polysaccharide Microgels of Varying Crosslinking Density

Crosslinking chains of amphiphilic polymer suspended in solution yields microgel particles. Due to the properties of the parent polymer, microgels undergo reversible temperature dependent de-swelling. Our microgels were synthesized from a polysaccharide, hydroxypropylcellulose. Static light scattering (SLS) was used to determine the molecular weight, Mw, the radius of gyration, Rg, and the second virial coefficient, A2, of synthesized microgels at varying cross-linker density. However, proper SLS measurements require determination of the specific refractive index increment (dn/dc) for the samples studied. This project is focused on dn/dc measurements for microgel samples of varying crosslinking concentrations. The dn/dc values were found to have a temperature dependence as well as a crosslinker concentration dependence at higher crosslinker concentrations. Here we present how dn/dc results affect the obtained Mw, Rg, and A2 of the microgels and show the importance of direct dn/dc measurements for the samples studied by SLS.