机械研究二维共价有机框架从最初同质的条件迅速聚合
Brian J Smith1, William R Dichtel
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University , Ithaca, New York 14853-1301, United States.
Journal of the American Chemical Society
|June 4, 2014
概括
我们研究了同质条件下的共价有机框架 (COF) 的生长. 这使我们能够量化COF-5形成动力学,并确定提高材料质量的反应参数.
科学领域:
- 材料科学 材料科学 材料科学
- 聚合物化学 聚合物化学
- 纳米技术 纳米技术
背景情况:
- 聚合有机框架 (COF) 是具有可调节结构和高表面积的先进多孔材料.
- 了解COFs的核和生长动力学对于改善其结晶性和实现合理合成至关重要.
- 目前研究COF形成的方法受到异质反应条件的限制.
研究的目的:
- 在同质反应条件下研究2D酸 Ester-linked COF-5形成的动力学.
- 为了建立反应参数和COF材料质量之间的第一个定量联系.
- 为了获得对COF核和生长过程的机械洞察力.
主要方法:
- 在完全溶解的单体条件下合成COF-5.
- 使用光学度测量量COF降水率的量化.
- 动力分析包括温度依赖 (阿雷尼乌斯) 和速率定律的确定.
主要成果:
- 观察到COF-5的形成在同质条件下在几分钟内发生.
- 该反应表现出阿雷尼乌斯温度依赖,激活能量为22-27kcal/mol.
- 率法被确定为酸和甲基醇部分的第二顺序,反之,甲醇度的第二顺序.
- 固体测量水添加导致晶石域面积增加了四倍,证明了对材料质量的合理控制.
结论:
- 均的合成条件使COF形成的严格动力学研究成为可能.
- 该研究提供了第一个定量动力学数据和对COF生长的机械洞察力.
- 反应条件,特别是水固态度,可以合理控制,以显著提高COF结晶体域大小和材料质量.
相关概念视频
01:09Radical Chain-Growth Polymerization: Mechanism
2.9K
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...
2.9K
00:57Cationic Chain-Growth Polymerization: Mechanism
2.1K
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...
2.1K
01:04Anionic Chain-Growth Polymerization: Mechanism
1.7K
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...
1.7K
01:17Ziegler–Natta Chain-Growth Polymerization: Overview
2.3K
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...
2.3K
01:10Radical Chain-Growth Polymerization: Overview
2.7K
Chain-growth or addition polymerization is successive addition reactions of monomers with a polymer chain. In radical chain-growth polymerization, the reaction proceeds via a free-radical intermediate. The free radical is formed from radical initiators, which spontaneously generate free radicals by homolytic fission. Organic peroxides (such as dibenzoyl peroxide, as shown in Figure 1) or azo compounds are popular radical initiators. A low concentration ratio of radical initiator to monomer is...
2.7K
02:34Polymers
32.8K
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...
32.8K