Microfluidic-Assisted Synthesis of Waterborne and Solvent-Free Urea-Crosslinked Polydimethylsiloxane Microparticles

Submillimetric and highly monodisperse urea‐crosslinked polydimethylsiloxane microparticles are synthesized without solvent with a microfluidic‐assisted process comprising a co‐axial capillaries microdevice. This device allows for the continuous‐flow production of double droplets in a stream of an aqueous solution. The core of the droplets is composed of a pure isocyanate compound (IPDI). The shell is composed of either a dicarboxylic‐acid‐functionalized silicon oil or a PDMS‐amide prepolymer resulting from the reaction of the former silicon oil with an amine compound (Jeffamine). By preventing the isocyanate groups to get in contact with the water, the shell phase constrains the polyaddition reaction inside the droplets, leading to the formation of urea‐crosslinked polydimethylsiloxane microparticles in the size range of 580–620 μm. Double droplets of isocyanate core and dicarboxylic‐acid‐functionalized silicon oil or PDMS‐amide prepolymer shell in water are produced by means of a capillary‐based microfluidic process. This drop‐in‐drop stucture allows avoiding direct contact of isocyanate groups with water and results in the waterborne and solvent‐free formation of urea‐crosslinked PDMS microparticles having an extremly narrow size distribution.