Poly (l-Lactic acid)/silk fibroin composite membranes with improved crystallinity and thermal stability from non-solvent induced phase separation processes involving hexafluoroisopropanol

The crystallinity of semi-crystallized Poly (l-Lactic acid) (PLLA) is low, especially as a porous membrane prepared from non-solvent induced phase separation (NIPS) process. To improve the crystallinity and thermal stability of PLLA porous membranes, hexafluoroisopropanol (HFIP) was added into the PLLA casting solution together with a small amount of Silk Fibroin (SF). It is found that by optimizing the additive amounts of HFIP and SF, PLLA composite membranes with improved crystallinity (up to 47.1%) and endurance to temperature (above 90 °C) could be prepared with comparable mechanical property to the virgin PLLA membranes. The effects of HFIP in NMP solution on PLLA during the NIPS process was further investigated using dynamic rheological methods relating to the crystallinity of the formed PLLA porous membranes.