Constrained crystallization of poly(L-lactic acid) in thin films prepared by dip coating

Dip coating process used at various withdrawing speeds showed a great ability to control the crystalline structure of thin films of poly(L-lactic acid) which can be of great importance for applications where mechanical or optical properties are involved. Thin films were studied by Atomic Force Microscopy and Grazing Incidence Angle X-ray Diffraction. Withdrawing the silicon substrate in the draining regime (at high speeds) led to amorphous films with flat surface whatever the solvent and the molar mass. At low speeds (capillary regime), AFM demonstrated the presence of spherulites or hedrites in the films depending on the solvent and the molar mass. GIXRD showed that spherulites were less crystallized than hedrites. This difference was attributed to solvent evaporation rate.