Polymeric microspheres preparation by membrane emulsification-phase separation induced process

•An emulsion is generated by injecting the polymeric solution through the membrane.•The continuous phase allows the phase inversion and precipitation of the polymer.•Droplets formation and solidification occur in a single step.•Membrane emulsification was combined with phase inversion method.•Uniform PES microspheres with target size have been produced.

Uniform Polyethersulfone (PES) microspheres of target size in the range of 30–60 µm were successfully prepared by combining membrane emulsification technology and phase separation induced process in one step. An emulsion is generated by injecting the polymeric solution through a microporous membrane into the continuous phase which allows also the phase separation induced process and precipitation of the polymer (coagulation bath). Therefore, the droplets formation and solidification occur in a single step. Furthermore, the preparation of non-aqueous (O/O) emulsions by membrane emulsification as well as the preparation of polymeric microspheres by non-solvent induced phase separation has never been reported previously. The effect of continuous phase-coagulation bath composition, hydrophobic emulsifier, dispersed phase flux and shear stress on size and uniformity of PES microspheres has been investigated. Key factors in microspheres production by membrane emulsification and phase separation induced process mechanism include the solvent/non-solvent system type, non-solvent composition and O/O interface composition. Polymeric microspheres with spherical morphology have been produced by tailoring such key factors.