Formation, morphology and control of high-performance biomedical polyurethane porous membranes by water micro-droplet induced phase inversion

Biomedical polyurethane (BPU) porous membranes with controlled morphology and excellent permeability and mechanical properties were prepared via a method involving a phase inversion induced by water micro-droplets, which were generated by an ultrasonic atomizer. The cross-section morphology, air permeability and mechanical properties of the porous membranes were investigated. The SEM images demonstrated that the adjacent pores were connected by a micro-hole, serving as a “backdoor” for the pore. An interconnected porous structure was obtained, improving the air permeability of the BPU membrane relative to the membrane produced by immersion precipitation. Our studies indicated that the diameter of the pores in the membrane depended on the solution viscosity, allowing porous membranes with a desired morphology to be obtained by adjusting the polymer concentration and solution viscosity. The application of micro-droplets of water during membrane preparation reduced the exchange rate between the solvent and nonsolvent, resulting in the microphase separation of polymer molecules and the formation of a uniform porous structure in the membrane, which improved the air permeability and mechanical properties of the BPU porous membranes. This is a simple and effective preparation method for high-performance porous membranes with potential applications in tissue engineering scaffolds, controlled-release drug delivery and vascular grafts.