Electrospun polylactic acid non-woven mats incorporating silver nanoparticles

This research is focused on the influence of silver nanoparticles (AgNPs) on the spinnability, morphology and wetting properties of electrospun polylactic acid (PLA) non-woven mats. PLA was electrospun from a chloroform solution (4.7 % g/g) and a filament and beads morphology was obtained, the filaments having an average diameter of 1.25 mu m. Interestingly, water contact angle measurements showed a contact angle of theta = 81A degrees, an improvement relative to as-cast film which exhibited a contact angle of theta = 54A degrees. When AgNP, of ca. 12 nm size, were incorporated at 1 % g/g relative to PLA weight, to the 4.7 % PLA-chloroform solution, and electrospun, the filaments diameter was greatly reduced to an average of 0.65 mu m, and the density of polymer beads was also reduced. It is believed that the electric conductivity of silver enhanced the spinnability of the polymer solution. Strikingly, water contact angle measurements showed that the PLA/AgNP mats exhibited an angle as high theta = 134A degrees. Increasing the solution concentration to 6.7 % g/g still produced a beads-and-filament morphology, but with larger filament diameters, probably due to an increase in solution viscosity. When AgNP were added (again at 1 % g/g relative to PLA weight), the occurrence of beads diminished and the average filament diameter decreased confirming the enhancement in spinnability by the AgNPs. Moreover, contact angles remained above 110A degrees suggesting that the overall morphology is key to PLA's mats hydrophobic behavior and not only filament diameter. Finally, the non-woven mats were rather amorphous, as revealed by differential scanning calorimetry and X-ray scattering, due presumably to the quenching process associated with the electrospinning process.