Tailoring morphology and crystallinity of poly(L-lactide acid) electrospun membranes

Abstract

Biodegradable poly(L-lactide acid) (PLLA) microfibers were prepared by electrospinning by varying applied potential, solution flow rate and collector conditions. Smoothly oriented and random fiber morphologies of PLLA were obtained and characterized by scanning electron microscopy. Optimum fiber orientation was obtained at 1000 rpm in a 20,3 cm diameter collecting drum, while for higher or lower drum rotation speeds, the fast random motions of the jets result in a random fiber distribution. The jet deformation with fast solidification during electrospinning often results in a meta-stable phase. PLLA eletrospun fibers are amorphous but contain a large number of crystal nuclei that rapidly grow when the sample is heated in the temperature range between 70 and 140ºC. In this way, the degree of crystallinity of the samples can be further tailored by temperature annealing from amorphous PLLA up to samples with 50% crystallinity. The infrared spectra show that the processing conditions do not affect the PLLA samples at a molecular level. Moreover, the infrared spectra reveal that the crystallinity of the samples is related to the presence of  crystals.