Systematic study on interfacial polymerization mechanism of toluene diisocyanate and water for the preparation of polyurea microspheres

Abstract

• Droplets-based microfluidics is used to generate TDI droplets in aqueous phase. • Polyurea microspheres were prepared by interface polymerization of TDI with water. • Interface polymerization mechanism of TDI with water is studied in details. Polyureas (PU) are important materials in wide range of applications from protective coatings and catalyst supports to biomaterials for drug release and hydrogels. However, it has been a challenging task to prepare porous PU with definite form or shape limited by the nature of the PU synthesis, that is, precipitation polymerization. New chemical and physical techniques of PU synthesis have gained great attention in order to fabricate these materials with diverse morphologies and structural features. In this communication, droplet-based microfluidics approach is adopted to convert conventional precipitation polymerization of PU synthesis to interface polymerization and PU microspheres with porous morphology are prepared. In this process, first toluene diisocyanate (TDI) droplets were generated in flowing PVA aqueous solution inside a tube and then converted to uniform porous PU microspheres through interface polymerization. The interface polymerization mechanism is discussed in details by controlling the polymerization time. It was found that polymerization of TDI with water was started at the interface of TDI droplet and water, and PU shell was formed around the TDI droplets, leading to formation of microcapsules. After the formation of PU shell, polymerization was continued inside the microcapsule by the diffusion of water molecules through the PU shell until all the TDI was finished and PU microspheres with porous morphology were obtained. This communication provides therefore a systematic study on interfacial polymerization of TDI with water to get porous PU microspheres and enabling technical advantages for potential applications to get PU materials with specific shapes and textural modifications.