• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Studies of the ring-opening polymerization of cyclic ethers and esters by coordinate catalysis.
【24h】

Studies of the ring-opening polymerization of cyclic ethers and esters by coordinate catalysis.

机译：通过配位催化研究环醚和酯的开环聚合。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

From the reactions between 2,2'-ethylidenebis(4,6-di- tert-butylphenol) and 2,2'-methylidenebis(4-di-methyl-6-di- tert-butylphenol) and Et2AlCl the biphenoxide complexes [(O∼∼CHMe∼∼O)AlCl]2, 1, and [(O∼∼CH 2∼∼O)AlCl]2, 2, have been characterized. These dimers are broken up by donor ligands and in THF give [(O∼∼CHMe∼∼O)AlCl(THF)], 3. Racemic 5,5'-6,6'-tetra-methyl-3,3 '-di-tert-butyl-1,1'-biphen-2,2 '-diol and Et2AlCl react in hexane to give [(O∼∼O)AlCl] 2, 6. In THF, monomeric species such as (O∼∼O)AlX(THF) (X = Et, 5, Cl, 4) are formed. Compounds 1, 2, 3, 4, 5, 6 act as propylene oxide, PO, polymerization catalyst precursors. The polymers have been examined by MS techniques and NMR spectroscopy. The new Al compounds give close to 50:50 HH to TT junctions. Polymerization of S-PO and 50:50 mixtures of S-PO and rac -PO reveal that the stereoirregular polymer is formed by a stereoselective ring-opening step. An analysis of the HH and TT junctions at the triad level suggests that polymerization occurs by a cationic coordinate mechanism by back-side attack on an activated PO molecule, leading to inversion at the methine carbon.; The aluminum chloride complexes mentioned above are shown to be inactive in initiating the ring-opening polymerization, ROP, of lactides, LA. Upon addition of PO, they lead to block oligomers/polymers of the form (PPO) n(PLA)m. The copolymers have been characterized by 1H, 13C NMR spectroscopy, by mass spectrometry (GPC/ESI/MS and LD/FTMS) and gel permeation chromatography. The Union Carbide catalyst system, [Ca(NH2)(OiPr)], is active in ROP of lactides at room temperature as well as PO. Compounds [(O∼CHMe∼O)Al(mu-O iPr)]2 and TPPAlOMe (TPP = tetraphenylporphyrin) are active in PO polymerization at room temperature but will effect lactide ROP only upon heating to 80°C. The stereoselectivity exhibited in ROP of PO by the porphyrin and the Union Carbide catalyst systems is not observed for ROP of rac-LA. These results are discussed in terms of the intimate mechanism of ring-opening of PO and lactides, where it is proposed that coordinate catalysts differ in their operation. (Abstract shortened by UMI.)
机译：从2,2'-亚乙基双（4,6-二叔丁基苯酚）与2,2'-亚甲基双（4-二甲基-6-二叔丁基苯酚）和Et2AlCl之间的反应，联苯醚氧化物配合物[[表征了O ～～ CHMe ～～ O）AlCl] 2，[[O ～～ CH 2〜O）AlCl] 2。这些二聚体被供体配体分解，并在THF中得到[（O ~~ CHMe ~~ O）AlCl（THF）]，3。外消旋5,5'-6,6'-四甲基-3,3'-二叔丁基-1,1'-联苯-2,2'-二醇与Et2AlCl在己烷中反应，生成[（O ~~ O）AlCl] 2、6。在THF中，诸如（O ~~形成O）AlX（THF）（X ＝ Et，5，Cl，4）。化合物1、2、3、4、5、6充当环氧丙烷PO聚合催化剂前体。通过MS技术和NMR光谱检查了聚合物。新的Al化合物使TT连接处的HH接近50:50。 S-PO和S-PO与rac -PO的50∶50混合物的聚合表明，立体不规则聚合物是通过立体选择性开环步骤形成的。对三元组水平的HH和TT结的分析表明，聚合反应是通过阳离子配位机理发生的，该机理是对活化的PO分子的背面攻击，导致次甲基碳的转化。已证明上述氯化铝络合物在引发丙交酯LA的开环聚合ROP中是惰性的。加入PO后，它们会形成（PPO）n（PLA）m形式的嵌段低聚物/聚合物。共聚物已通过1 H，13 C NMR光谱，质谱（GPC / ESI / MS和LD / FTMS）和凝胶渗透色谱进行了表征。联合碳化物催化剂体系[Ca（NH2）（OiPr）]在室温下对丙交酯的ROP和PO具有活性。化合物[（O-CHMe-O）Al（mu-O iPr）] 2和TPPALOMe（TPP =四苯基卟啉）在室温下具有聚合活性，但仅在加热至80°C时才会发生丙交酯ROP。对于rac-LA的ROP，未观察到卟啉和联合碳化物催化剂体系在PO的ROP中表现出的立体选择性。根据PO和丙交酯的开环的密切机理来讨论这些结果，其中提出了配位催化剂的操作不同。 （摘要由UMI缩短。）

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号