A supercritical CO2 assisted electrohydrodynamic process used to produce microparticles and microfibers of a model polymer

An evolution of traditional electrospray and electrospinning is proposed in this work, adding SC−CO2 in the liquid polymeric solution. This new process arrangement allows to overcome some intrinsic limitations of the traditional processes, namely surface tension and viscosity control. The influence of various process parameters was studied. The increase of electric potential difference did not significantly modify the particle size distributions and the fiber size distributions; but, the distributions became sharper as the electric potential difference increased. At low PVP percentages in the solution, electrospray was favored, forming small particles, due to low solution viscosity. The viscosity of the solution increased with PVP concentration: therefore, first large and very large particles were formed; then, the process was no more able to produce jet break-up, microfibers were obtained and the process was converted to electrospinning, producing microfibers with diameters down to about 1.4 μm. Using lower molecular weight PVP, smaller particles (down to 0.35 μm) were produced and the particles/fibers transition occurred at larger polymer percentages. Pressure and PVP percentage played opposite roles in generating the different morphologies; therefore, electrospray and electrospinning assisted by SC−CO2 are like two faces of the same medal: they could be performed using the same apparatus, properly setting the process conditions and polymer concentration.