Study On Structure Control And Application Of Polylactic Acid Electrospun Membrane Reinforced By Modified Cellulose

As one of the most significant methods for fabricating nanofibrous membranes,electrospining have attracted considerable attention because electrospun fibers enjoy unique features such as large specific surface areas,high porosities,controllable diameters and adjustable morphologies.Electrospining poly lactic acid(PLA)nanofibers has been wildily investigated over several decades since the excellent properties of biodegradbility and good biocompatibility.Therefore,it has been wildly used in the biomedical field especially for use in medical dressings and drug carriers.However,some limitations including poor mechanical,thermal properties which lead to obviously burst release,low dispersity of hydrophilic drug loading and poor adsorption capacity.Therefore,to overcome the above prolems,in this paper,we would plan to prepare PLA nanocomposites fibrous membranes by addition of modified cellulose nanocrystals.The introduction of modified cellulose nanocrystals into the PLA matrix enhanced the mechanical properties,thermal properties and hydrophilicity and achieve sustained drug release.The following is the main research contents:(1)A wide range of parameters affecting the morphology of electrospun fibers while the solution properties(viscosity,surface tension and electrical conductivity)are the crucial factors.In this paper,the interaction between solution properties and fibrous diameters was investigated by changing solvent ratio and solution concentration.The relationship between solution properties and fibrous diameter was analyzed by SPSS software and obtained the prediction formula of nanofiber diameters.Therefore,the diameters of the fiber was controlled by adjusting the property of the solution.(2)The compatibility between cellulose nanocrystals and polylactic acid matrix was improved by grafting maleic anhydride and L-lactide on the surface of cellulose nanocrystals.Thus,the mechanical properties,thermal properties and hydrophilicity of the modified composite fibrous membrane were enhanced.The tensile strength of the fibrous membranes in the maleic anhydride modified nanocrystals system increased by1.74 times,the initial decomposition temperature increased to 296 °C,the contact angle was reduced to 87.3°.The tensile strength of composite fibrous membranes in the Llactide modified system increased by 2.32 times.The initial decomposition temperature increased to 289 ? and the contact angle decreased to 78°.(3)Smooth fibrous membranes,bead-on-string fibrous membranes and porous fibrous membranes were prepared by modified morphologies.Bead-on-string drug loaded fibers effectively allievated the drug burst release which could result from smooth drug loaded fibers.For smooth PLA nanofibers encapsulating drugs,the drug release rate of was 60% while beaded composite drug loaded fibers was only 30%.Porous composite fibrous membranes enhanced drug adsorption capacity and increase water retention and specific surface area.In detail,the drug adsorption capacity,water retention and specific surface area were increased by 1.91 times,1.8 times and 4.64 times respectively.Therefore,the porous fiber is more suitable for medical dressings.