Model-based prediction of the hydrodynamic radius of collapsed microgels and experimental validation

Microgels are functional colloidal polymer networks with diverse applications. Various applications require microgels of different sizes. The microgel size is determined during the synthesis and depends among other conditions on the reactor type, reactor temperature, monomer-to-initiator ratio, cross-linker concentration, and surfactant concentration. While experimental data covering these synthesis conditions are available in literature, a model taking into account all of the above factors has not yet been proposed. We present a mechanistic model considering all of the above conditions that agrees with experimental data from various literature sources. The effect of surfactant type and concentration is included by addition of a term in the coagulation kinetics. The reactor type and Reynolds number in the reactor is accounted for with a semi-empirical parameter describing the kinetics of particle coagulation. This parameter is fitted to the data of one of the available experiments, while all other experiments are used for validation. The model predictions quantitatively match the experimental data for stirred batch reactors. For unstirred batch reactors, the agreement with the experimental data is only qualitative. The mechanistic model enables model-based design of functional microgels for new applications.