The Effects of Crosslinker on Polymeric Microgels*

Microgels are nanoparticles suspended in solution and comprised of crosslinked polymer chains. Due to the amphiphilic property of the parent polymer, microgels exhibit a reversible volume phase transition, de-swelling with an increase in temperature. Microgels in this study were synthesized by crosslinking hydroxypropylcellulose (HPC) in a surfactant solution. The amount of crosslinker used for synthesis was varied by a factor of a hundred. Using dynamic light scattering, microgels were characterized at various temperatures and scattering angles to determine the particles’ hydrodynamic radius (Rh) and dynamics both in the swollen and de-swollen states. It was shown that for low crosslinker concentrations, microgels exhibit standard behavior, with a decrease in radii as crosslinker concentration increases. Above a certain concentration, the behavior switches from standard behavior to microgel growth with temperature increase. Also observed was that some particles exhibiting standard microgel behavior increase in size at very high temperatures, possibly due to non-uniform crosslinker distribution.