Physico chemical and phase separation characterization of high molecular PLLA blended with low molecular PCL obtained from solvent cast processes

Blends of PLLA and PCL yielded by solvent casting usually exhibit phase separation and crystallization behavior which have a strong impact on their suitability for certain biomedical applications such as degradable coatings or drug carriers. Therefore, it is important to understand the underlying mechanisms. In this study, high-molecular biodegradable semi-crystalline poly(L-lactide) (PLLA) (Mw = 320 kDa) was blended with low-molecular biodegradable semi-crystalline poly(ε-caprolactone) (PCL) (Mw = 40 kDa) in various combinations (10, 50 and 90 wt.% PCL) by solvent casting. The yielded blends were subjected to annealing at 40 °C, 80 °C and 200 °C and cooled down slowly to maintain thermodynamic equilibrium. Scanning electron microscopy, atomic force microscopy, Raman images and differential scanning calorimetry were used to investigate the structure, morphology and thermal properties of the solvent cast PLLA/PCL blends. It was shown that the physico-chemical properties of PLLA/PCL blends prepared by solvent casting differ substantially compared to those accessed by melt manufacturing processes. In summary, the blends showed a complex phase separation behavior, which is completely dependent on the method of preparation and the adjusted temperature during production process.