Ultrasonication-induced and diluent-assisted suspension polymerization for size-controllable synthesis of polydimethylsiloxane droplets

초록

Submicroscale polydimethylsiloxane (PDMS) spheres are emerging as a promising solution for a variety of engineering applications due to their unique material properties and size. It is, however, still considered as challenging to produce submicroscale PDMS droplets. This leads to the need for development of a deterministic method for producing size-controllable, monodisperse PDMS droplets and, by extension, comprehensive understanding of the physicochemical players and processes involved in the synthesis method. Here, we develop an ultrasonication-induced and diluent-assisted (UIDA) suspension polymerization process to achieve the scalable synthesis of monodisperse PDMS droplets. The UIDA suspension polymerization process is essentially the same as conventional suspension polymerization processes except ultrasonic agitation and organic diluent addition. The use of ultrasonication is intended to controllably reduce the size of PDMS droplets, while the addition of a diluent to PDMS is designed to enhance the monodispersity of PDMS droplets (major) and decrease their size (minor). First, we explore the dependence of PDMS droplet size and polydispersity on rudimentary factors such as stabilizer (i.e., polyvinyl alcohol (PVA)), magnetic stirring, ultrasonication, diluent (i.e., benzene), and synthesis vessel. Next, a time-variant change in the size and size distribution of PDMS droplets under UIDA suspension polymerization process are investigated by deconvoluting the droplet dispersity in size into two components, each of which is described using an envelope of the log-normal distribution. The main cause of a bimodal distribution is also identified. Finally, we demonstrate the applicability of PDMS droplets in altering the hydrodynamic properties of polymer surfaces by fabricating a set of rose petal-inspired substrates through evaporation coating of PDMS droplets on flat PDMS surfaces. The findings of this study will lead to better understanding of suspension polymerization for synthesizing monodisperse submicroscale droplets made of thermosetting polymers.

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