稀土催化剂催化己二酸酐开环聚合

【作者】 任世剑；

【导师】 沈之荃； 凌君；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2004， 硕士

【摘要】 聚酸酐是一类新型的可降解生物医用高分子材料，近年来因其在人工器官、药物控释等方面的潜在应用价值而倍受关注。开环聚合具有聚合条件温和、能有效控制聚合物的分子量、分子量分布以及聚合物结构等优点，是合成可降解生物医用高分子材料的重要手段。研究酸酐开环均聚及其与脂肪族内酯、环碳酸酯等的共聚对于开发新型可降解生物医用高分子材料具有重要意义。目前酸酐聚合的大多数催化剂是烷基金属、烷氧基金属等。迄今为止，尚未见芳氧基稀土催化剂催化己二酸酐开环聚合的报道。本文首次应用低毒性的芳氧基稀土催化剂——三（2，6-二叔丁基-4-甲基苯氧基）镧在温和的条件下单组分催化己二酸酐的开环均聚及其与2，2-二甲基三亚甲基环碳酸酯、己内酯的共聚，研究了溶剂、温度、聚合时间、单体催化剂比例等因素对聚合的影响，并使用¹H NMR、DSC、GPC、MS、PLM等手段对聚合物进行了表征。 首次使用三（2，6-二叔丁基-4-甲基苯氧基）镧催化己二酸酐开环均聚合，聚合具有高活性。当[AA]／[La（OAr）₃]=500、[AA]=1.0 mol／L、二氯甲烷溶剂、20℃，AA聚合60 min，转化率达到86.0％，PAA通过“端基分析法”分子量为1，500。DSC检测到3个结晶熔融峰：51.4、64.5和108.9℃。 首次使用三（2，6-二叔丁基-4-甲基苯氧基）镧催化己二酸酐与2，2-二甲基三亚甲基环碳酸酯、己内酯的嵌段共聚，制备了一系列不同单体比例的嵌段共聚物，共聚物结构通过GPC、¹H NMR、DSC等手段表征证实。 （[AA]+[DTC]）／[La（OAr）₃]=500、[AA+DTC]=3.0 mol／L、AA／DTC=50.0／50.0、二氯甲烷溶剂、25℃，聚合30 min得到的poly（DTC-b-AA），经GPC测定M_n=12.3×10⁴、M_w／M_n=1.64，¹H NMR分析共聚物中DTC／AA=34.1／65.9，DSC检测到56、65和103℃ 3个结晶熔融峰。共聚合机理研究发现，首先La（OAr）₃催化DTC单体酰氧键断裂开环形成La—OCH₂C（CH₃）₂活性中心并生成PDTC活性链段。随后，AA单体通过酰氧键断裂插入上述烷氧镧活性中心，形成羧基镧活性中心，完成PAA链段聚合。研究发现AA单体形成的羧基镧活性中心对DTC单体开环没有活性。 （[AA]+[CL]）／[La（OAr）₃]=500、[AA+CL]=2.0 mol／L、AA／CL=49.4／50.6、浙江大学硕士学位论文二氯甲烷溶剂、25℃，聚合30 min得到的Poly（CL一乃一AA）经GPC测定MI、二5，2“1少、M.v/MI，二1 .13，‘H NMR分析共聚物中cUAA约为l，Dsc曲线有55.3、71 .3和119.7oc3个结晶熔融峰。共聚合机理研究发现，首先La（O付）3催化CL单体酚氧键断裂开环形成La一oc玩C场CHZc玩C玩活性中心并生成PcL活‘{生链段。随后，AA单体通过酞氧键断裂插入上述烷氧钢活性中心，形成狡基钢活性中心，进而完成PAA链段聚合。更多还原

【Abstract】 Polyanhydride, as a new biodegradable polymer, for its potentialities in design of artificial organs and drug delivery systems has attracted ever-increasing attention recent years. Ring opening polymerization (ROP) provides a direct access to the related polyanhydrides and is most likely the best way of avoiding all disadvantages of the traditional polycondensation method. To study the homopolymerization of anhydride and the copolymerization of anhydride with aliphatic cyclic esters and carbornates is significant for the development of the new biodegradable polymers. However, almost all the catalysts reported for the ROP of adipic anhydride (AA) are alkyloxide metal or alkyl metal. To the best of our knowledge, the ROP of AA catalyzed by rare earth aryloxide has not been reported so far. In this paper, lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) was firstly applied to catalyze the ROP of AA and the copolymerization of AA with CL or DTC. The polymer structures are identified by GPC, 1H NMR, DSC, MS and PLM.Lanthanum tris(2,6-di~tert-butyl-4-methylphenolate) was firstly used to catalyze the ROP of AA, exhibiting high catalytic activity. Poly(adipic anhydride) (PAA, Mn = 1,500) was obtained with a conversion of 86.0% within 1 hr in methylene chloride at 20 ℃. Three melting peaks were found in the DSC curve of the polymer at 51.4, 64.5 and 108.9 ℃, respectively.Block copolymers of AA with CL or DTC were prepared by La(OAr)3 for the first time, respectively, and the copolymer structures are identified by GPC, 1H NMR and DSC.poly(DTC-b-AA) with Mn = 12.3 x 104, Mw/Mn = 1.64, DTC/AA = 34.1/65.9 was prepared by block copolymerization of DTC with AA in methylene chloride at 25 ℃ by using La(OAr)3 as catalyst. Three melting peaks were found in the DSC curve of the copolymer at 56, 65 and 103 ℃. The copolymerization mechanism was proved to be a "coordination anionic mechanism". DTC monomer coordinated to rare earth metal on the carbonyl group, and opened ring via acyl-oxygen bond cleavage to form a "living" chain with the end group- La-OCH2C(CH3)2, then the AA monomer insert into the La-0 bond to form the PAA block. However, the end group of PAA-La-OOCCH2CH2CH2CH2 shows no catalytic activity to the ROP of DTC.poly(CL-b-AA) with Mn = 5.2xl04. Mw/Mn = 1.13, CL/AA = 1 was prepared by block copolymerization of CL with AA in methylene chloride at 25 ℃ by using La(OAr)3 as catalyst. Three melting peaks were found in the DSC curve of the copolymer at 55.3, 71.3 and 119.7℃. The copolymerization mechanism was proved to be a "coordination anionic mechanism". CL monomer coordinated to rare earth metal on the carbonyl group, and opened ring via acyl-oxygen bond cleavage to form a "living" chain with the end group- La-OCH2CH2CH2 CH2CH2, then the AA monomer insert into the La-0 bond to form the PAA block. However, the end group of PAA-La-OOCCH2CH2CH2CH2 shows no catalytic activity to the ROP of CL.更多还原