化二氧化 () 复合物,用于活体,的异选择性聚合:多块异性聚烯共聚物,通过连续的单体添加
Joseph B Edson1, Zhigang Wang, Edward J Kramer
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, USA.
Journal of the American Chemical Society
|March 19, 2008
概括
新的催化剂使活体,异选择性烯聚合成为可能. 这一突破允许合成具有高延长性质的新型弹性块共聚合物.
科学领域:
- 聚合物化学 聚合物化学
- 有机金属化学 有机金属化学
- 材料科学 材料科学 材料科学
背景情况:
- 开发有效的催化剂用于控制的聚合,对于先进的材料合成至关重要.
- 复合物为聚合催化提供可调节的特性.
- 活体和异选择性聚合是创建定义良好的聚合物架构的关键.
研究的目的:
- 为了合成和评估 bis ((phenoxyketimine) 二化物复合物作为活体的催化剂,同选择性烯聚合.
- 为了研究连接物替代剂对催化剂性能的影响.
- 使用优化的催化剂系统合成新型块共聚物.
主要方法:
- 合成双二化物复合物 (二) 的合成.
- 用甲基氨酸 (MAO) 激活催化剂.
- 烯聚合研究以评估活性,活力和异选择性.
- 块共聚合物的合成和表征.
- 合成块共聚合物的机械测试.
主要成果:
- 胺替代物的身份显著影响了催化剂活性和同选择性.
- 通过MAO激活的复合体12显示出有效的生存,异选择性烯聚合 ([m4] = 0.73,alpha = 0.94).
- 成功合成了各种与等离子聚烯和聚乙烯共聚烯块的区块共聚合物,包括triblock,pentablock和heptablock结构.
结论:
- 双二化物复合物是活的有效催化剂,异选择性烯聚合.
- 开发的催化剂系统能够合成复杂的块共聚合物架构.
- 由此产生的弹性体块共聚物具有优良的机械性能,在断裂时具有很高的延伸度 (790-1000%).
更多相关视频
07:28Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
Published on: November 27, 2015
10:53Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by π-π Stacking Interactions
Published on: October 10, 2016
相关概念视频
02:35Free-Radical Chain Reaction and Polymerization of Alkenes
The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
01:17Ziegler–Natta Chain-Growth Polymerization: Overview
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...
01:26Polymer Classification: Stereospecificity
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
00:57Cationic Chain-Growth Polymerization: Mechanism
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...
01:13Olefin Metathesis Polymerization: Overview
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
01:04Anionic Chain-Growth Polymerization: Mechanism
The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael acceptor.