Control of structure and morphology of highly aligned PLLA ultrafine fibers via linear-jet electrospinning

In this work, poly(l-lactic acid) (PLLA) ultrafine fibers with different morphology and structure were fabricated by a novel linear-jet electrospinning method which relies on a conventional electrospinning set-up with continuous rotating drum. To control the morphology and structure of PLLA electrospun fibers, different solution systems and electrospinning conditions were investigated. Two PLLA solution systems (PLLA/DMF/CH2Cl2 and PLLA/CH2Cl2) with different concentration and conductivity were used for the electrospinning and their influences on the formation of the linear electrospinning jet were discussed. Two types of collecting patterns with aligned buckling and linear structure were achieved under the linear electrospinning jet. Highly aligned PLLA electrospun fibers with porous surface could be formed by using the highly volatile solvent CH2Cl2. Here, it should be emphasized that the diameter and surface porosity of such highly aligned PLLA electrospun fibers can be fine tuned by varying the winding velocity. The results of SEM images and polarized FTIR investigations verified that the as-spun PLLA porous surface fibers were highly aligned and molecularly oriented, leading to the enhanced mechanical performance as compared to the non-woven PLLA electrospun fibers.