The Study Of Controllable Electrospinning Polylactide-based Porous Fibers

In this work,the porous fibers of polylactide acid（PLLA）,poly（lactide acid-co-caprolactone）（poly（LLA-co-CL））andpolylactideacid/polyaniline（PANI）/camphorsulfonic acid（CSA）were prepared.The condition for the preparation of controllable porous fibers were studied by changing the proportion of components,the parameters of electrospinning,the properties of the solvents and the electrical conductivity of polymer solution.The morphology and physical properties of the prepared fibers were also characterized.This thesis consisted of the following three parts:（1）The effects of volatility and boiling temperature for electrospun solvent on the prepared porous PLLA fibers were studied.The results showed the porosity decreased with the increase of the boiling point of solvent.And the porous PLLA fibers could be prepared by phase separation from the rapid evaporation of solvent or the addition of non-solvent.The tensile strength would decrease with the increased porosity of fibers.The BET results showed the fibers specific surface area would be greater with smaller diameter and more pores.The fibers diameter had a greater influence on the specific surface area than porous structure.The contact angle（CA）test showed CA would increase with the increase of specific surface area or porous structure,thus increased hydrophobicity.（2）The effects of solvent volatility and solubility of different segments on the porous fibers of the copolymer were studied.The properties of the fibers could be controllable by changing the content of different segments in copolymer and properties of electrospinning solution.The SEM results showed the fibers diameter influenced by the electrical conductivity of solvent.The volatility and the solubility for the different segments of the solvents were the main factors that affecting the porosity of fibers.The mechanical test showed the fibers tensile strength decreased with the increase of porosity.Compared with PLLA fibers,when the content of CL segments in copolymer was within 10%,the porosity was the main factor that influencing the mechanical properties.The tensile strength decreased as CL segments content increased.However,when the content of CL segments increased to 30%,the segment content was the main factor that influencing the mechanical properties of the fibers and the tensile strength was significantly enhanced.BET results indicated the smaller diameter and the more porous structure,the fibers specific surface area would be greater.CA test indicated the hydrophobicity of fiber membranes was enhanced with the increase of the BET specific surface area or porosity.（3）The effects of solvent electrical conductivity on porous fibers were studied.The spinning voltage was set at 10 kV,SEM results showed the fibers porosity and diameter decreased as the electrical conductivity of the spinning solution increased.After the doping of CSA in the solution of PLLA/PANI,the electrical conductivity increased to 0.507μS/cm,and the porous structure in the fibers surface was disappeared.While the pores were appeared again with increasing the voltage to 14 kV.FTIR results approved the structure of PLLA/PANI/CSA composite fibers.DSC showed adding PANI could improve melting point（T_m）and glass transition temperature（T_g）of PLLA fibers,but the addition of CSA would reduce the T_m and T_g of PLLA/PANI fibers.The mechanical properties test showed the tensile strength of the fibers were enhanced by the rigid chain of PANI molecular.While the tensile strength of PLLA/PANI fibers will be reduced with the addition of CSA dopant.The BET results indicated when increased the spinning voltage to 14 kV,PLLA,PLLA/1P,PLLA/5P,PLLA/1P/1C fibers diameter significantly decreased and the pores on fibers surface increased,which could effectively increase specific surface area.The CA test indicated the amino groups in PANI（-NH-）and sulfonic acid groups（-SO₃H）in CSA could effectively improve hydrophily.For the same components of polymers,the larger specific surface area or the more porous structure,the contact angle would be greater.