Effect of Film Formation Method and Annealing on Morphology and Crystal Structure of Poly(L-Lactic Acid) Films

The poly(L-lactic acid) (PLLA) has potential medical usage such as drug delivery since it can degrade into bioabsorbable products in physiological environments, while the degradation is affected by its crystallites. In this paper, the effects of film formation method and annealing on the crystallites formed in PLLA films are investigated. The films are made through solvent casting and spin coating, and subsequent annealing is conducted. The resulting morphology, molecular order, conformation, and intermolecular interaction are examined using optical microscopy, wide-angle X-ray diffraction, and Fourier transform infrared spectroscopy. It is observed that solvent casting produces category 1 spherulites while annealing the spin coated films leads to spherulites of category 2. The crystal structure of the two kinds of films also shows distinct features. The results enable better understanding of the crystallites in PLLA, which is essential for its medical application.