Spectroscopic study on water diffusion in poly(lactic acid) film

The diffusion of water in biocompatible semicrystalline poly(lactic acid) (PLA) is investigated using time-resolved ATR-FTIR. There are three different states of water molecules diffusing into the film. Using a 2D correlation analysis, the diffusion process and the role of different functional groups on diffusion is obtained. First, the moderately strongly bound water forms a hydrogen bond with -C=O. Then, the water diffuses into free volume (microvoids) and strong hydrogen bonds are formed between two -C=O groups and water. The conformations of semicrystalline PLA change during the diffusion process and recover after re-drying. In addition, water first interacts with amorphous segments and then interacts with crystalline segments.