LAUSR

Abstract Polyureas (PU) are of prime importance for a great number of applications from protective coatings and catalyst support to biomaterials for hydrogels and drug release. Novel physical and chemical methods of their synthesis have been great interests in order to obtain these materials of different morphologies with different surface and structural properties. Herein, PUs with exotic structures, including bead-skewer and string-form, are prepared through a very simple interfacial polymerization of toluene diisocyanate (TDI), by adding it into an aqueous solution of ethylenediamine (EDA) at constant rate. The effects of experimental conditions, including EDA/TDI ratio, polymerization temperature, pore size of syringe needle for TDI addition and the addition rate, on the morphology of PU materials were studied. The results showed that bead-skewer PU was obtained with EDA/TDI ratio at 1.43–1.51, and string-form PU achieved with the same ratio at 1.59–2.20. A hard shell was first formed on the surface of TDI once extruded out of the syringe needle. The size of bead-skewer and string-form PU was easily adjusted. Their chemical structure characterization by NMR confirmed that a PU shell was formed in the early stage of the polymerization, owing to the reaction of TDI with EDA. PU materials thus prepared are macroporous regardless of their shape. This paper provides therefore a novel and simple way to the preparation of porous PU with specific shapes, such as bead-skewer and string-form, along with the formation and shape transition mechanism of the materials.