Electrospinning Poly(Lactic Acid) With A Bimodal Inter-Fiber Pore Size Distribution
This research concerns the fabrication of electrospun Poly(lactic acid) membranes onto a patterned surface to produce a bimodal pore size distribution as well as the control of fabric properties via control of fiber properties. In the case of patterned electrospinning, a grid substrate was utilized to selectively collect electrospun fibers in desired locations while amassing fewer fibers between the grid wires. Membranes produced from grids with 3mm or 5mm spacing between copper wires possessed bimodal inter-fiber pore size distributions. Membranes produced from grids with 1mm spacing between copper wires had no significant difference in pore size distribution when compared with control samples prepared on flat copper sheets. The pore size distribution affects membrane wettability. It is shown that membranes possessing small pore sizes and small pore size distributions absorb more wetting liquid than membranes with large pore sizes and large pore size distributions. This phenomenon results from capillary action. The capillary action equation can be modified to model the pores as a series of interconnected spheres. Determining the number of pores of a given size remains a challenge, but with an appropriate pore number approximation, this equation has the potential to provide an accurate prediction of absorbency for a given membrane. Fiber morphology and ionicity was altered by modifying applied electrospinning voltage, spinning dope solvent concentration, and ionic filler concentration. These variations did not affect fiber properties significantly enough to alter load sharing in the full membrane; thus, compliance was not significantly affected by changes in fiber qualities.
dissertation or thesis