發(fā)布時(shí)間：2018-04-16 15:23

  本文選題：聚乳酸 + 聚ε-己內(nèi)酯　； 參考：《吉林大學(xué)》2017年碩士論文

【摘要】：聚乳酸(PLA)和聚ε-己內(nèi)酯(PCL)作為領(lǐng)先的生物可降解合成聚酯,已經(jīng)引起人們?cè)絹?lái)越多的關(guān)注。較比于直接聚合,開(kāi)環(huán)聚合(ROP)丙交酯(LA)和ε-己內(nèi)酯(ε-CL)單體能夠獲得高分子量的PLA和PCL產(chǎn)物。對(duì)于LA的聚合,異構(gòu)體的作用對(duì)所得PLA材料的物理、機(jī)械、流變和降解性能至關(guān)重要。金屬配合物能夠良好地控制PLA結(jié)構(gòu)和性能是生產(chǎn)PLA最有效的方法,包括分子量、組成、微結(jié)構(gòu)和單體結(jié)合等方面,尤其是立體選擇性ROP,所得PLA的立構(gòu)規(guī)整度,顯著影響其物理和化學(xué)性能�；�于我們前期的工作,第一部分我們以三種雙金屬中心席夫堿鋁配合物催化LA和ε-CL開(kāi)環(huán)共聚,制備了一系列不同單體比例的共聚物。利用核磁(NMR)結(jié)果分析測(cè)定了共聚物中LA與ε-CL結(jié)構(gòu)單元的比例及平均鏈段長(zhǎng)度。通過(guò)對(duì)左旋丙交酯(L-LA)和外消旋丙交酯(rac-LA)分別與ε-CL開(kāi)環(huán)共聚反應(yīng)的動(dòng)力學(xué)性能進(jìn)行對(duì)比研究,發(fā)現(xiàn)該催化體系中LA的聚合速率快于ε-CL,而L-LA的聚合速率又略快于rac-LA。由此可以推知:所得共聚物為微觀組成漸變的梯度共聚物。利用DSC對(duì)所得共聚物進(jìn)行了熱力學(xué)性能表征,發(fā)現(xiàn)隨著兩種結(jié)構(gòu)單元比例的變化,共聚物的玻璃化轉(zhuǎn)變溫度(T_g)呈現(xiàn)規(guī)律性變化。鑒于金屬配合物很難從聚合產(chǎn)物中分離干凈從而限制材料的應(yīng)用,人們更愿意使用無(wú)毒金屬(鋅)配合物催化環(huán)酯開(kāi)環(huán)聚合。第二部分我們基于烯醇式配位結(jié)構(gòu),成功設(shè)計(jì)、合成和表征了一系列烯醇式單金屬中心鋅配合物,作催發(fā)劑催化LA、ε-CL開(kāi)環(huán)聚合。研究發(fā)現(xiàn)烯醇式鋅配合物在聚合LA過(guò)程中表現(xiàn)出較高活性,催化劑苯環(huán)取代基的存在和配位胺橋的增長(zhǎng),易于單體配位插入的關(guān)系,能夠顯著提高催化劑的活性,配合物4a表現(xiàn)出最高的催化活性。聚合結(jié)果還發(fā)現(xiàn)催化體系異丙醇加入與否,對(duì)催化聚合反應(yīng)并無(wú)影響,聚合物端機(jī)和NMR結(jié)果分析表明加入異丙醇并不參與配位。
[Abstract]:Polylactic acid (PLA) and poly (蔚 -caprolactone) (PCL) have attracted more and more attention as a leading biodegradable synthetic polyester.Compared with direct polymerization, ring-opening polymerization (ROP) lactide (LA) and 蔚 -caprolactone (蔚 -CL) monomers can obtain high molecular weight PLA and PCL products.For the polymerization of LA, the action of isomers is very important to the physical, mechanical, rheological and degradation properties of the obtained PLA materials.The structure and properties of PLA can be well controlled by metal complexes, which include molecular weight, composition, microstructure and monomers, especially stereoselective PLA.The physical and chemical properties are significantly affected.Based on our previous work, in the first part, a series of copolymers with different monomer ratios were prepared by the ring-opening copolymerization of LA and 蔚 -CL catalyzed by three kinds of bimetallic center Schiff base aluminum complexes.The ratio of LA to 蔚 -CL units and the average length of chain segments in the copolymers were determined by NMR.The kinetic properties of the ring-opening copolymerization of L-LLA and rac-lactide with 蔚 -CL were compared. It was found that the polymerization rate of LA was faster than that of 蔚 -CLand and the polymerization rate of L-LA was a little faster than that of rac-LA.It can be inferred that the obtained copolymer is a gradient copolymer with gradual microstructure.The thermodynamic properties of the copolymers were characterized by DSC. It was found that the glass transition temperature (TG) of the copolymers changed regularly with the change of the ratio of two structural units.In view of the fact that metal complexes are difficult to separate from polymeric products and thus limit the application of materials, nontoxic metal (zinc) complexes are preferred to catalyze the ring-opening polymerization of cycloesters.In the second part, based on the enol coordination structure, a series of enol monometallic zinc complexes were successfully designed, synthesized and characterized, which were used as catalysts to catalyze the ring-opening polymerization of LA-CL.It was found that the enol zinc complex exhibited high activity during the polymerization of LA. The presence of benzene ring substituents and the increase of the coordination amine bridge of the catalyst could improve the activity of the catalyst.Complex 4a showed the highest catalytic activity.The polymerization results also showed that the addition of isopropanol had no effect on the catalytic polymerization. The results of polymer terminal and NMR showed that the addition of isopropanol did not participate in the coordination.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：O643.3;O631.5

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