A facile route to preparation of uniform polymer microspheres by quiescent polymerization with reactor standing still without any stirring

This paper presents a novel and facile route to preparation of highly uniform polymeric microspheres through a quiescent polymerization with the reactor standing still without any stirring. Using one single monomer, isophorone diisocyanate (IPDI), highly uniform polyurea microspheres are achieved with high yield via precipitation polymerization of IPDI with water in water–acetone mixed solvent. Full conversion of IPDI to polymer is readily achieved thanks to the step polymerization mechanism involved. The monomer concentration can go up to 11 wt.% with the polymerization accomplished within 2 h, with a much higher yield of microspheres in a much shorter time than those reported with vinyl monomers. The size of the microspheres is adjustable by changing IPDI concentration, acetone/H2O ratio in the solvent or polymerization temperature. Without need of any stirring or shaking during the polymerization, the protocol renders the fabrication of uniform microspheres more practical and economical, particularly for large scaled production.

Graphical abstractHighly uniform microspheres bearing amine groups on the surface were prepared using one single monomer, isophorone diisocyanate (IPDI), via step polymerization with water in water–acetone mixture. The process was accomplished within 2 h with the bottle reactor standing still without any stirring or shaking. The size of the microspheres was adjustable from 2 to 10 μm by changing IPDI concentration, acetone/H2O ratio or polymerization temperature.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Highly uniform polymer microspheres are prepared without any stirring. ► The process is featured by step polymerization of isocyanate and water. ► No residual monomer exists at end of process due to step polymerization mechanism. ► Much higher microsphere yield achieved in much shorter time than those reported. ► Size of the microspheres easily adjustable by changing polymerization conditions.