Fabrication And Application Of Porous Poly(L-lactide) Micro-Spheres/Fibers/Films

As an important field of material science,porous materials have been widely applied in biology,medicine,chemistry and chemical engineering due to their low density,high strength and high surface area.Various fabrication strategies have been developed to improve the surface area.The porous nano-materials are significant for this purpose as well as the different requirements in practical applications.In this work,therefore,the PLLA/PEO blend has been employed because of the environment-friendly properties of PLLA,the crystallization behaviors of PEO and the special miscibility between them.With the combination of“top-down”and“bottom-up”strategies,the porous PLLA micro-spheres,fibers and films have been fabricated by electrospray?3D confined?,electrospinning?2D confined?and spin-coating?1D confined?respectively.Furthermore,the control of pore sizes and morphologies has been achieved successfully.Scanning electron microscopy?SEM?,and transmission electron microscopy?TEM?were used to evaluate the pore structures.The special crystallization behaviors are investigated by DSC?Differential Scanning Calorimeter?and XRD?X-ray diffraction?.The resultant porous materials were applied in the adsorption,separation and shape memory.1.Porous PLLA microspheres made by electrospray and their application of drug loading:Porous PLLA microspheres are fabricated by electrospray?3D confined?PLLA/PEO?polyethylene oxide?blend solution and subsequent removal of PEO by water etching.Our results show that the porous PLLA microspheres with continuous nanochannels inside have been successfully fabricated and the size of microspheres and nanochannels can be adjusted by the blend ratio of PLLA/PEO.In the electrospray,PEO crystallized and produced an interpenetrating network with amorphous PLLA,accounting for the formation of the porous PLLA microspheres upon water etching.These microspheres can absorb BSA?Bovine Serum Albumin?,which exhibits pH sensitivity.The BSA adsorption is the highest at the pH of 5.2.Porous PLLA fabrics made by electrospinning and their application of oil adsorption,emulsion separation and loading Ag nanoparticles:Porous fibers and resultant fabrics are fabricated by electrospinning?2D confined?PLLA/PEO?polyethylene oxide?blend solution and subsequent removal of PEO by water etching.The formation mechanism of porous structures is much like the porous microspheres.The roughness in micro-and nano-scales enlarges the wettability difference between oil and water,resulting in the superhydrophobic and superoleophilic membrane.As a result,the hierarchically porous PLLA fabrics possess high flux in the separation of water-in-petroleum ether emulsion driven solely by gravity.The flux summed up to 1.13×10⁴±576L·m^-2·h^-1.The Ag nanoparticles can be loaded facilely to the open pores of fabrics to prepare an excellent anti-bacterial membrane.3.Porous PLLA membranes made by spin-coating and their shape memory effect:Porous PLLA films were prepared by spin-coating PLLA/PEO blend solution and selectively removal of PEO by water etching.The DSC results suggest the very low crystallinity of PLLA.Consequently,the tiny PLLA crystals act as the shape-fix phase while the amorphous parts serve as the shape-recovery phase.The PLLA porous films exhibit excellent shape memory performance with 100%shape fix ratio and shape recovery ratio.And amazingly,these micropores can completely copy the deformation of the whole film during uniaxial and biaxial tensions.According to the discussion above,a novel strategy for fabricating porous shape-memory membrane has been developed.