Chloroform micro-evaporation induced ordered structures of poly(l-lactide) thin films

Self-assembly of poly(l-lactide) (PLLA) in thin films induced by chloroform micro-evaporation was investigated by microscopic techniques and X-ray diffraction studies. A film-thickness dependent on highly ordered structures has been derived from disordered films. Ring-banded spherulitic and dendritic morphologies with radial periodic variation of thicknesses were formed in dilute solution driven by micro-evaporation of the solvent. Bunched morphologies stacked with a flat-on lozenge-shaped lamellae were created in thinner films. The formation of the concentric ring banded structures was attributed to the periodic rhythmic growth associated with radial periodic changes in the concentration gradient of PLLA. A diffusion-induced rhythmic growth mechanism was proposed to explain the formation of the ring banded morphologies with periodic variation of thicknesses.