基基对有机催化乙烯聚合物的影响. 向着同时引入多聚烯分支和功能组的方向
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Journal of the American Chemical Society
|April 6, 2006
概括
这项研究引入了5-hexenylsilane作为乙烯聚合中的共纳体,产生了西兰终结共聚合物. 这种功能性共纳体通过一种新的链转移机制有效地控制聚合物分子重量.
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:
- 有机催化剂广泛用于olefin聚合.
- 控制聚合物分子量和结构对于定制材料特性至关重要.
- 功能化共纳体提供了同时聚合和链修饰的潜力.
研究的目的:
- 使用有机介导的聚合物合成以烯终结的乙烯/5-基烯共聚合物.
- 为了研究5-hexenylsilane作为共和链传递剂的作用.
- 建立一种用于控制聚合物分子重量的新方法,并引入烯功能.
主要方法:
- 使用5-hexenylsilane作为共同分子进行有机介导的乙烯聚合.
- 使用1H和13C NMR光谱学对共聚物组成和结构的表征.
- 用凝浸透色谱 (GPC) 分析分子重量分布.
- 通过差分扫描热量计 (DSC) 评估的热性能.
主要成果:
- 实现了高的聚合活性 (高达107g聚合物/mol Ti.atm乙烯.h) 和狭窄的聚分散性.
- 聚合物分子重量与5-hexenylsilane度呈反向关系,表明有效的链转移.
- 与n-hexylsilane相比,5-hexenylsilane显示出更高的链传输效率.
- 这项研究成功地产生了西终结乙烯共聚合物.
结论:
- 在有机介导的乙烯聚合过程中,5-hexenylsilane 作为有效的共和链转移剂.
- 提出了一种分析链传递机制,并得到实验证据的支持.
- 这项工作呈现了功能化共纳体的第一个实例,有效地调解烯聚合物的传播和链转移,为聚合物设计开辟了新的途径.
更多相关视频
09:12Functionalization of Single-walled Carbon Nanotubes with Thermo-reversible Block Copolymers and Characterization by Small-angle Neutron Scattering
Published on: June 1, 2016
11:09Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness
Published on: April 1, 2018
相关概念视频
02:34Polymers
The word polymer is derived from the Greek words “poly” which means “many” and “mer” which means “parts”. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the properties that they exhibit. Additionally,...
01:09Radical Chain-Growth Polymerization: Mechanism
The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this species into the...
01:17Radical Chain-Growth Polymerization: Chain Branching
The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
01:20Anionic Chain-Growth Polymerization: Overview
The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
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.
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,...