Porous electrospun PCL fibres in a single step by phase separation

Porous polycaprolactone (PCL) nanofibers were produced by phase separation during electrospinning in a single step process using binary solvent systems with a broad range of properties which consisted of a mixture of a good solvent for PCL such as chloroform (CF), dichloromethane (DCM), tetrahydrofuran (THF) and formic acid (FA), and a poor solvent such as dimethyl sulfoxide (DMSO). Phase separation was induced when the good solvent evaporated leaving a solution of PCL rich in poor solvent resulting in saturation of the solution and phase separation. The effect of the solution properties and of the ratio of good/poor solvent to the morphology of the fibres and pore formation mechanism were studied. The production of porous, bead free fibres was achieved in CF/DMSO solution with good/poor solvent ratios varying from 75-90% v/v. The ternary mixture compositions that lead to the formation of porous fibres were mapped on a ternary graph. The pore formation was favoured at high good/poor solvent ratios, whereas, the production of fibres with ribbon cross sections or fibres with beads was more pronounced at low good/poor solvent ratios. The effect of the process parameters (flow rate, voltage, distance) on the pore covered area were also studied and voltage was found to exert the strongest effect on fibre morphology while increasing the process parameters led to increased pore coverage.