Preparation and morphology control of porous microspheres of different crystalline polymers

PCL and PLA have good biocompatibility and degradability, which are widely used in biomedical fields. Here, PDLLA, PLLA and PCL porous microspheres with different crystallinities were prepared using the single emulsion solvent evaporation method. The effects of polymer crystallinity, molecular weight, concentration and temperature on the morphology of microspheres were systematically studied, and flat porous and concave porous microspheres were accurately prepared. Petroleum ether, n-dodecane and paraffin liquid were used as alkane porogens. DSC and XRD showed that the crystallinity of PDLLA, PLLA, and PCL increased in turn. Porous microspheres with different morphologies were prepared using three different porogens. The results showed that the polymer microspheres with different crystallinities have different morphologies, including concave porous and flat porous microspheres. Different types of porogens have the greatest influence on the morphology of PLLA microspheres while having little effect on PCL and PDLLA. The larger the molecular weight of PDLLA microspheres, the larger the particle size. The phase separation trend of low molecular weight PCL and high concentration porogen increased, and it facilitated easy formation of hollow porous and bowl-shaped microspheres, which affected the integrity of the microspheres. The mechanism of the microsphere morphology can be analyzed and attributed to two main processes, namely polymer phase separation and organic solvent volatilization. This study provides an effective strategy for the precise preparation of microspheres with a porous morphology.