Properties of aligned poly(L-lactic acid) electrospun fibers

Poly(L-lactic acid) (PLLA)-aligned fibers with diameters in the nano- to micrometer size scale are successfully prepared using the electrospinning technique from two types of solutions, different material parameters and working conditions. The fiber quality is evaluated using scanning electron microscopy (SEM) to judge fiber diameter, diameter uniformity, orientation, and appearance of defects or beads. The smoothest fibers, most uniform in diameter and defect free, were found to be produced from 10% w/v chloroform/dimethylformamide solution using an accelerating voltage from 10-20 kV. Addition of 1.0% multiwalled carbon nanotubes (MWCNT) into the electrospinning solution decreases fiber diameter, improves diameter uniformity, and slightly increases molecular chain alignment. The fibers were cold crystallized at 120 degrees C and compared with their as-spun counterparts. The influences of the crystalline phase and/or MWCNT addition were examined using fiber shrinkage, temperature-modulated calorimetry, X-ray diffraction, and dynamic mechanical analysis. Crystallization increases the glass transition temperature, T-g, slightly, but decreases the overall fiber alignment through shrinkage-induced buckling of the fibers when heated above T-g. MWCNT addition has little impact on T-g, but significantly increases the orientation of crystallites. MWCNT addition slightly reduces the dynamic modulus, whereas crystallization increases the modulus in both neat- and MWCNT-containing fibers. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41779.