淀粉/DL-丙交酯接枝共聚物的合成和生物降解性能研究

STUDIES ON SYNTHESIS AND BIODEGRADABILITY OF STARCH/DL-LACTIDE GRAFTING COPOLYMER

以淀粉为接枝骨架 ,DL 丙交酯为接枝单体 ,在无水LiCl存在下 ,合成了淀粉 /DL 丙交酯接枝共聚物 .研究了接枝反应的投料比、反应时间、反应温度对单体转化率 (C % )、接枝率 (G % )和接枝效率 (GE % )的影响 .当DL 丙交酯与淀粉结构单元的摩尔比为 10∶1,反应温度为 80～ 85℃ ,反应时间为 4h ,C % ,G %和GE %可分别达到 37 3 %、179 7%和 6 8 0 % .用差示扫描量热 (DSC)分析仪、红外光谱仪和X 射线衍射仪对合成的接枝共聚物进行了表征 ,结果表明 ,淀粉和DL 丙交酯反应生成了淀粉 /DL 丙交酯接枝共聚物 .防水实验结果表明 ,该产物在给定条件下可使纸板的吸水率由 41 1%降低到 1 0 % .降解实验表明该接枝共聚物能够被酸。

A novel grafting copolymer was synthesized by reacting DL lactide with corn starch in N,N dimethylacetamide (Me\-2NAC) in the presence of triethylamine(NEt\-3) and anhydrous lithium chloride.The effect of reaction time and the molar ratio of DL lactide to structural unit of starch on monomer conversion( C %),grafting ( G %) and grafting efficiency( GE %) has been studied.The C %, G % and GE % could approach 37.3%,179.7% and 68.0%,respectively when the molar ratio of DL \|lactide to structural unit of starch is 10∶1,the grafting copolymerization was carried out at 80～85℃ for 4h in a nitrogen atmosphere.Several techniques such as Fourier transform infrared(FTIR) spectroscopy,differential scanning calorimetry (DSC) and X\|ray diffraction (XRD) were used to characterize the grafting copolymer.FTIR spectrum shows an absorption band at 1740cm -1 confirming the formation of ester bond,indicating the starch/ DL lactide grafting copolymer was produced.The DSC characteristic result showed the melting temperature of the grafting copolymer elevated slightly as the molar ratio of DL lactide to glucose structural units of starch increased and the X ray diffraction pattern showed the synthesized grafting copolymer was an amorphous copolymer.The degradability of grafting copolymer was tested with the aid of acid,alkali and microbe.The weight loss of the grafting copolymer was 100% after 70h in 0.5mol/L hydrochloric acid solution at 30℃,but the weight loss of the grafting copolymer approaching to 100% after 35h in 0.2mol/L sodium hydroxide solution at 30℃,the weight loss of the glucose structural unit of starch and DL polylactide chain in the grafting copolymer was 41.8% and 24.0% after 20 days and 30 days of incubation with bacillus subtilis and staphylococcus aureus at 37℃ respectively.The grafting copolymer produced can be used as a component in hot\|melt adhesives and as an impermeable coating for paper and cardboard.