聚乳酸/醋酸纤维素复合多孔超细纤维的制备

FABRICATION OF PLLA/CA COMPOSITES POROUS ULTRAFINE FIBERS

以DMF／二氯甲烷（DCM）或丙酮／DCM为溶剂，通过静电纺丝制备了直径为0．89-1．21μm、孔径大小为61-123nm的PLLA／CA复合多孔超细纤维．探讨溶剂组成、溶剂比例、聚合物浓度和环境湿度对纤维直径、孔径大小和比表面积的影响．通过SEM观察纤维形貌及其孔径大小，通过N2吸附-脱附曲线计算多孔纤维的比表面积．实验结果表明，相比较丙酮／DCM和DMF／DCM溶剂，以丙酮／DCM为溶剂所制备的纤维孔径小、比表面积大．主要因为丙酮／DCM沸点低，溶剂挥发过程越剧烈，聚合物温度降低越多，热致相分离越剧烈，越有利于形成密集的孔．且混合溶剂中随着DCM比例的增加，纤维上的孔密度和比表面积都增加．聚合物浓度从3％增加到15％，形貌从“多孔颗粒”过度到“珠-串多孔纤维”直到最后生成均匀无珠多孔纤维．纤维上纳米孔的形成主要是由于静电纺丝过程中溶剂的快速挥发引起纤维表面温度急剧降低导致热致相分离而产生多孔结构．且纤维中形成了相互贯穿的三维连通孔．因此可以判断此体系主要是旋节相分离机理进行相分离．

PLLA/CA composites porous ultrafine fibers with diameters of 0. 89 -1.21μm and mesopores of 61 -123 nm were prepared by electrospinning using DMF/DCM or acetone/DCM as solvent. The effects of composition of solvent,ratio of solvent,concentration and environment humidity on the diameter and porosity of PLLA/CA composites porous ultrafine fibers were investigated. The fiber diameter and surface morphology were studied using scanning electron microscopy （SEM） , and specific surface area was calculated by N2 adsorption/ desorption isotherms. The PLLA/CA composites porous uhrafine fibers electrospun from acetone/DCM showed smaller pore diameter and larger specific surface area compared with those from DMF/DCM solvent. This was attributed to the boiling point of acetone/DCM was lower than that of DMF/DCM,the more decrease of polymer temperature when solvent was volatized, the sharper thermal induced phase separation, so the density of pore was increased. Moreover, with increasing of DCM content, the density of pore and specific surface area of PLLA/CA composites porous ultrafine fibers were increased. With increasing of polymer concentration from 3 % to 15% ,the morphology was transformed from ＂ porous particle＂ to ＂bead on the string＂ ,and finally forming uniform porous fibers. The characteristic PLLA/CA porous fibers was formed by thermal induced phase separation （TIPS） mechanisms,because of the sharp temperature drop caused by the quick solvent evaporation in the electrospinning process. Moreover, because the interconnected porous structure was formed, the phase separation took place in a spinodal decomposition mechanism in this system.