Investigating Acrylic Acid Polymerization by Using a Droplet-Based Millifluidics Approach

We present herein the basic concept of droplet-based millifluidics as an original tool to monitor polymerization kinetics. As a proof of concept, we use aqueous droplets of acrylic acid mixed with sodium persulfate at various pH as polymerization microreactor models. According to the pH and the temperature, completion could be obtained within a minute. Despite the fact that this reaction is quite fast and exothermic, we were able to acquire data in order to obtain valuable information about the polymerization kinetics. We were also able to estimate the overall activation energy for polymerization rate. Furthermore, offline analyses by Size Exclusion Chromatography show high molecular weights and high polydispersities. These results set the stage for further studies of polymerization reactions where detailed basic kinetic data must be acquired in conditions which cannot be investigated by using conventional batch glassware (i.e. high temperatures or concentrations). This new approach can also be used as an efficient High Throughput Screening tool.