Fabrication of hierarchical porous poly (l-lactide) (PLLA) fibrous membrane by electrospinning

Nanofibres with high surface area have various applications in many fields, such as filtration, tissue engineering and drug delivery. In the previous reported works, a lot of researchers have fabricated porous polymer nanofibres with porous surface structure, but few researchers could produce thoroughly hollow porous nanofibres by electrospinning. Here, we developed porous poly(l-lactide) (PLLA) fibres with good internal pore connection by two methods, i) removal of a pore-forming agent from PLLA composite fibres; ii) nonsolvent induced re-crystallization of pure PLLA fibres. In the first method, electrospun PLLA/cellulose acetate butyrate (CAB) composite fibres were immersed into acetone to remove CAB. Results showed that the fibres with less CAB could produce porous structures. However, with the increasing of CAB content, the fibre surface had only a collapsed structure. In the second method, while pure PLLA fibres were immersed into acetone, the solvent-induced recrystallization of PLLA generated porous structures throughout the whole fibres. Owing to the higher crystallization, the mechanical properties of PLLA fibres were also highly improved.