Construction And Their Application Of Three-Dimensional Nanofibrous Structure Based On High Molecular Weight Poly (Lactic Acid)

Electrospun fibers with the diameter of ten nanometers to several microns, forming a pile of random non-woven fiber material, have a great surface area, high porosity and interconnected three-dimensional network structure. In this dissertation, firstly high molecular weight poly(lactic acid) were synthsized by the direct polycondensation. And a series of polymer helical fibers including PLA/PBS, PLA/PEG and PLA/PBT-PTMG-PEG were fabricated by electrospinning. Subsquently, nanostructured biocomposite scaffolds of PLLA were prepared by electrospinning, and their biocompatiblilty was observed by cell culture. Finaly, a new heat-assisted compression method was introduced to enhance the phsical properties of the PLLA electrospun membranes. The characterization and observatiions were carried out by DSC, XRD, SEM, TEM, etc. 1. The high molecular weight PLA was sytheszied by the direct polycondensation, and the third component e. g.2,2-dimethylol propionic acid and pentaerythritol as co-momoner play an important part in the coupling of the PLLA chains. The direct polyconsation with the third component here was a simple and inexpensive method to synthezise high molecular weight PLA.2. A series of PLLA helical micro/nanofibers was studied by two-spinneret electrospinning. PLA/PBS, PLA/PEG and PLA/PBT-PTMG-PEG helical fibers spontaneously formed in the electrospnning process. And the prepared fibers were characterized by scanning electron microscopy (SEM).3. By blending with collagen (coll) or Hydroxyapatite (HA), or both for tissue engineering application, nanostructured biocomposite scaffolds of PLLA including PLLA/coll, PLLA/HA and PLLA/coll/HA scaffolds were prepared by electrospinning. The prepared scaffolds were observed the biocompatiblity by cell culture. Acorrding to the observation, the composite had better physical properties and cell adhesion than that of pure PLLA scaffolds, especially on PLLA/HA/collagen scaffolds.4. PLLA electrospun fiber membranes were treated with a simple post-processing to improve the crystallinity of the fiber membrane and the bonding among fibers. Based on the treatment, the mechanical properties of electrospun membranes significantly improved. PLLA electrospun membranes crystallized in a form and strong fiber-to-fiber bondings occurred with the aid of heat and compression. The tensile properties including tensile strength and modulus of membranes treated with a press at 6 MPa and a temperature at 60℃(80℃and 100℃) increased by more than 100% compared with those of the as-electrospun membranes. The heat-assisted process provides a simple method to enhance the mechanical properties of electrospun membranes. This simple method was potential for application in filtration, tissue engineering and protective clothings, and so on, attributing to the enhancement of the structural integrity and physical properties.