Dissertation > Excellent graduate degree dissertation topics show

Microwave radiation synthesis of poly-L- lactic acid

Author: DongTuanRui
Tutor: ChenYaShao
School: Shaanxi Normal University
Course: Polymer Chemistry and Physics
Keywords: Straight-chain poly-L- lactic acid Star- poly-L- lactic acid Microwave radiation Synthesis
CLC: R318.08
Type: Master's thesis
Year: 2008
Downloads: 47
Quote: 0
Read: Download Dissertation

Abstract


Polylactic acid (PLA) based on a renewable plant resources as raw material, after chemical synthesis, biological degradable polymers. Because of its good biodegradability and biocompatibility, and degradation and in vivo metabolite harmless carbon dioxide and water, it is made from a variety of biodegradable packaging materials, efficient, low toxicity biomedical materials such as drug release microspheres, surgical sutures, surgical fixation materials, so much in the field of environmental protection and medical attention. PLA often by direct polycondensation of lactic acid and lactide to ring-opening polymerization prepared by two methods. Prepared by the ring-opening polymerization of lactide PLA is the basic methods of industrial production, but the method exists multi-step, technical requirements, equipment investment, low yield, product cost of many defects, national researchers hopes to improve lactate this method of direct polycondensation, to obtain a short process, low cost, high molecular weight PLA. Microwave radiation, L-lactic acid as raw materials, SnCl 2 for the catalyst synthesis of poly-L-lactic acid having a straight chain and the star structure, using FTIR, NMR its structural characterization, and further GPC and DSC analysis of the product was subjected to optimize the synthesis conditions. (1) Synthesis of the microwave radiation conditions straight chain of PLLA under microwave irradiation, 120 ° C, negative pressure and under the protection of nitrogen, L-lactic acid monomer to dehydration treatment, and then adding a certain amount of the catalyst of SnCl 2 , under certain temperature and time so as to melt polycondensation. Until the end of the reaction after the product is first dissolved in chloroform, and then ethanol to fractional precipitation, the final product is placed in the vacuum oven drying, the use of FTIR, 1 H NMR, the product structure Characterization prove that the product was a poly-L-lactic acid (PLLA) having a straight chain structure. Further use of the GPC and DSC analysis of the synthetic product under different temperature and reaction time, to optimize the synthesis conditions obtained when the reaction temperature of 155 ° C, the reaction time of 3 h, the microwave radiation synthesis under conditions of negative pressure and nitrogen protection polylactic acid having a straight chain structure a viscosity-average molecular weight and glass transition temperature are high. The experimental results also concluded that the larger the size of the nitrogen flow rate of synthetic product color, small hour when large product purity nitrogen flow, nitrogen flow product of whiteness. (2) the star SPLLA under microwave irradiation synthesis under microwave irradiation, 120 ° C, L-lactic acid monomer under negative pressure and nitrogen protection dehydration processing, and then adding a certain amount of initiator the pentaerythritol and catalyst SnCl 2 under a certain temperature and time to melt polycondensation. Upon completion of the reaction after the product was first dissolved in chloroform, and then ethanol to fractional precipitation, the sample was then placed in the vacuum oven drying. By FTIR 13 the C NMR product structural characterization, prove that the product is a four-arm star structure of poly-L-lactic acid (SPLLA). Further use of GPC and DSC analysis of synthesized product under different temperatures and reaction times, to optimize the synthesis conditions obtained when the reaction temperature was 155 ° C, the reaction time was 7 h, the viscosity-average molecular weight of microwave radiation under the conditions of the synthesis of SPLLA and glass transition temperature are high. DMA of PLLA and SPLLA mechanical properties are analyzed and compared draw, SPLLA strain small, quick recovery, and is conducive to maintaining the characteristics of the product Dimensions.

Related Dissertations

  1. Studies on the Synthesis and Technology of Dipentaerythritol and Its Derivative,TQ223.164
  2. Synthesis and Characterization on Semi-Aromatic Polyamides Containing Benzoxazole Units,O633.5
  3. Hydrothermal Synthesis of Oxide Hollow Spheres,TB383.4
  4. Video Coding Research Based on Texture Characteristics,TP391.41
  5. Poetic alienation : graphics,J506
  6. Urothermal Synthesis, Structure and Characterization of Functional Coordination Polymers,O631.3
  7. The Total Synthesis of a Flavonoid Glycoside Apigenin-7-O-β-D-glucuronide,R284.1
  8. Flexible,rigid,Synthesis and characterization of mixed ligand complexes,O621.1
  9. Experiments on Microwave Radiation Activation YunNan Unburned Coal-gangue Concrete,TU528
  10. Study on the Synthetic Process of Vat Pink R,TQ616.2
  11. Study on the Mechanism of Night Temperature to Grain Filling of Inferior in Rice,S511
  12. Curing Mechanism and Properties of Fluorenyl Epoxy Resin,TQ323.5
  13. Study on Antioxidant Activities and Lipase-catalyzed Transesterification of Lard to Produce L-ascorbyl Fatty Acid Esters,TS202.3
  14. Research on the Physiology Mechanism of Grain Filling of inferior Grain during Day and Night Chemical Regulations,S511
  15. Expression of β-Catenin in Pig’s Ovary and the Effect of β-Catenin on Porcine Granulosa Cells Apotosis and Steroidogenesis Related Enzyme,S828
  16. The Research on Texture Synthesis Technology from Cloud Theory & Been Evolution Genetic Algorithm,TP391.41
  17. Synthesis and Structures of Metal (Mn, Zn and Sn) Complexes Incorporating with the Sily-linded Bis (Amidinate) Ligands,O621.2
  18. The Oxidation Mechanism and Stability Improved of Conjugated Polyunsaturated Fatty Acids,O621.25
  19. The Synthrsis of Novel Purine Nucleoside Modified by C~6-Alkyl and C~6-Heterocyclic,TQ460.1
  20. More than enough calcium and magnesium metal ligand complexes Synthesis, Structural Characterization and Antibacterial Activity,O641.4
  21. Schiff base Synthesis, Characterization and Antibacterial Properties,O641.4

CLC: > Medicine, health > Basic Medical > Medical science in general > Biomedical Engineering > General issues > Biomaterial
© 2012 www.DissertationTopic.Net  Mobile