Fabrication of Porous Poly (L-lactic acid)/Graphene Electrospun Fibres

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Abstract

Porous materials enter people's field of vision and are widely used due to high specific surface area and porosity. This project firstly adjusted the concentration of poly (L-lactic acid) (PLLA) and N,N-dimethylformamide (DMF) in dichloromethane (DCM) solution to obtain the best ratio to fabricate relatively fine and uniform electrospun fibres from the PLLA pellets with an ultra-high MW of 1,340,000 g/mol. The results show that the S-PLLA2 .0DMF5.0 solution was the optimal one and prepared the electrospun film with a fibre diameter of 3.1 ± 0.5 μm. Secondly, to improve the performance of the PLLA electrospun fibrous film for broader application by the introduction of graphene oxide (GO) or reduced graphene oxide (rGO), the GO flakes with different size were ultrasonically coated on the PLLA electrospun films with different morphology and structure. The GO flakes used were SGO and LGO. The PLLA electrospun films used were M1, the bare-corncob-like F-PLLA2.0DMF5.0 film with post-treatment of acetone, M2, the F-PLLA2.0DMF5.0 Film possessing relatively smooth fibre, and M3, the F-PLLA2.0DMF0.0 film having droplet-like pores on the fibre surface. The results show that the surface morphology of PLLA electrospun film and the flake size of GO directly affected the GO coating, and also affected the subsequent GO reduction by L-ascorbic acid (LAA). Among these three films, the M1 film was the least friendly to the LGO coating but with relatively even distribution of GO flakes on the surface. The introduction of GO and the reduction of LAA both increased the crystallinity of the amorphous PLLA electrospun fibres. The introduction of GO by ultrasonic coating technique changed the PLLA electrospun fibre from hydrophobic to super-hydrophilic and increased the mechanical strength of PLLA electrospun films. The introduction of LrGO increased the hydrophobicity of the M2 and M3 films. The introduction of SrGO not only improved the mechanical strength but also increased the strain at break of the M1 film. Considering the properties of the porous PLLA/Graphene electrospun composites comprehensively, the SGO-coated M1 film was expected to become a biomaterial because SGO was relatively uniformly distributed on the membrane, made the membrane super-hydrophilic and improved mechanical properties; while the LrGO-coated M3 film was expected to become a water-oil separation material because the introduction of LrGO further improved the hydrophobicity and mechanical properties of the film.

Keyword(s)

Electrospinning; Graphene; Poly (L-lactic acid); Porous material

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