The Regulation And Control Of Pla Electrospun Fibers And Its Application

Poly(lactic acid)(PLA), a biodegradable and biocompatible polymer material have been attracted much attention in many fields as for biomedical, industrial packing,industrial separation. PLA has attracted more and more attention because of its good performance and it has become a new type of biodegradable polymer material. In order to expand scope of poly lactic acid’s application, many scholars focus on the regulating and controlling the structure of PLA, including chemical modification, physical processing and the combination of chemical and physical methods to composite with other materials and to optimize the structure of PLA. In recent years, the popularity of polymer physical processing methods is the electrospinning. With the aid of electrospining, the PLA solution is drawn by the electric field and create electrospun fibers.The electrospun fibers has a high specific surface area, and is widely used in textile, biological medical suture, gloves, etc.. The PLA combined with the electrostatic spinning technology has successfully regulate and control the structure of the PLA expanding its application range. Hence, the thesis takes the electrospinning technology as the carrier, PLA as the material, focus on the crystallization properties of PLA and its application on drug deliver-release and oil/water emulsions separation. The research results are carried out as follows:(1) In the asymmetric poly(L-lactide)/poly(D-lactide)(PLLA/PDLA) blends the pre-existed stereocomplex crystals can impose confinement effects on homocrystallization of uncomplexed PLLA among them. However, confinement effects are very weak in the blend films due to relatively large PLLA domains distributed in the skeleton of stereocomplex crystals. As a comparison, in the electrospun blend fibers fine distribution of uncomplexed PLLA results in strong confinement effects. It is manifested by the significant decrease in the crystallization temperature and melting point. Even so, confinement effects have little influence onthe crystal form, and PLLA α-crystals prevail in the electrospun blend fibers after melt crystallization. Finally, confinement effects in the electrospun blend fibers depend on annealing temperatures and almost disappear while being annealed above the melting point of stereo-complex crystals.(2) The electrospun fibers made of polylactide(PLA) have been attracting much attention in many applications because of biodegradability and biocompatibility.Introducing porous structure into electrospun PLA fibers is helpful to enhance surface area and thus to extend their applications. Here we report a novel and facile route to produce highly porous structure in the electrospun PLA fibers by simple immersion in poor solvents. It arises from swelling and subsequent solvent-induced crystallization in the electrospun PLA fibers,depending on solvent polarity, immersion temperature and PLA molecular weight. The highly porous PLA fibers have a very large surface area of 137.7 m2 g-1, which is almost unapproachable by other routes. The highly porous structure of PLA193 k fibers is well in loading doxorubicin hydrochloride(DOX) while the pure PLA193 k fibers weak in loading DOX. In a short period,the delivering of drug of highly porous structure reachs to 20%where the comparison PLA fibers peaks to 80%. Therefore,the modified PLA fibers of highly porous structure can be well used in drug deliver-release system.(3) Ideal membranes towards separation of oil/water emulsions should have submicron pores and surface hydrophilicity. The membranes of PLA electrospun fibers are hydrophobic and their diameter range from 100 nm to 10 um, which is not suitable for oil/water emulsions separation. To decrease the diameter of PLA fibers and improve the hydrophily of PLA, the cellulose are coated onto PLA fibers. Hence,the composite membrane of PLA-cellulose is suitable for separation of emulsion.