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相关概念视频

Crown Ethers02:36

Crown Ethers

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Crown ethers are cyclic polyethers that contain multiple oxygen atoms, usually arranged in a regular pattern. The first crown ether was synthesized by Charles Pederson while working at DuPont in 1967. For this work, Pedersen was co-awarded the 1987 Nobel Prize in Chemistry. Crown ethers are named using the formula x-crown-y, where x is the total number of atoms in the ring and y is the number of ether oxygen atoms. The term 'crown' refers to the crown-like shape that these ether...
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Anionic Chain-Growth Polymerization: Overview01:20

Anionic Chain-Growth Polymerization: Overview

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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,...
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Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

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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...
2.2K
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

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Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous...
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Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

2.0K
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
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Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule02:17

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

13.9K
If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
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相关实验视频

Updated: Jun 2, 2025

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions
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阴离子调制诱导分子极性在三个组成部分的王冠以太系统.

Feiyan Liu1, Guoyong Chen1, Xiao Liu1

  • 1School of Chemistry and Chemical Engineering, Nanchang University, Nanchang, 330031, People's Republic of China. 352800220014@email.ncu.edu.cn.

Dalton transactions (Cambridge, England : 2003)
|January 13, 2025
PubMed
概括

新型皇冠以太材料表现出温度诱导的结构变化,导致可调节的物理性质. 一个化合物显示可切换的第二波生成 (SHG) 信号,为先进的光学应用提供了潜力.

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科学领域:

  • 材料科学 材料科学 材料科学
  • 晶体学 晶体学是指结晶学.
  • 超分子化学 超分子化学

背景情况:

  • 皇冠以太相变材料对外部刺激做出反应,其物理性质发生了变化.
  • 主机-客皇冠以太集成为先进的材料设计提供可调节的特性.

研究的目的:

  • 设计和合成新的宿主-客冠以太分子.
  • 研究这些新材料的结构性质关系,特别是它们的相位转换和光学/介电反应.

主要方法:

  • 通过p-trifluoromethylaniline (PTFMA) 与15-crown-5.5的反应合成[(PTFMA) 15冠-5)ClO4] (1) 和[(PTFMA) 15冠-5)PF6] (2).
  • 使用差分扫描热量计 (DSC) 进行相位过渡的表征.
  • 评估第二波 (SHG) 信号和介电响应.

主要成果:

  • 复合物1呈现出一个可逆的相变,从一个非中心对称的 (P21) 到一个中心对称的 (P21/c) 空间组,随着温度的增加.
  • 在化合物1中,这种过渡伴随着可切换的SHG信号和介电反应.
  • 化合物2显示可逆相变和介电反应,但缺乏可切换的SHG信号.

结论:

  • 阳离子的极性显著影响皇冠乙烯复合物的特性,影响SHG反应.
  • 这些发现为开发具有可切换光学特性的新冠乙烯复合物提供了洞察力.
  • 这项研究突出了设计的皇冠以太材料的潜力,用于需要刺激响应行为的应用.