Synthesis Optimization and Characterization of Polymeric Microgels

Microgels are spherical particles suspended in solution, comprised of crosslinked polymer chains. Due to the amphiphilic property of the parent polymer, microgels display a temperature dependent volume phase transition (de-swelling), and thus have the potential to be used for drug delivery. Microgels were synthesized using a polysaccharide polymer and cross-linker, in a surfactant solution. Synthesized particles were characterized using dynamic light scattering (DLS) for temperature and angular dependence to study their shape and determine the apparent hydrodynamic radius (R_h) of the swollen and de-swollen states. Previous studies suggest that increasing the concentrations of the chemical cross-linker reduces R_h and the de-swelling ability. Initial microgel synthesis revealed a dependence of R_h on microgel concentration in samples, requiring a correction factor during analysis. Primary experiments focused on the variation of cross-linker concentration ratios. Increasing the ratio from 1 to 30 causes R_h to decrease from 150 - 190 nm at 25^oC, and from 65 - 95 nm at 50^oC. Ratios from 30 to 50 resulted in swelling from 70 nm at 25^oC to 165 nm at 50^oC. At a ratio of 60, an apparent bulk gelation occurred.