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相关概念视频

Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

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The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
1.8K
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

5.7K
All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
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Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

2.2K
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
Radical Chain-Growth Polymerization: Overview01:10

Radical Chain-Growth Polymerization: Overview

2.3K
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...
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Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

2.5K
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
2.5K
Cycloaddition Reactions: MO Requirements for Photochemical Activation01:12

Cycloaddition Reactions: MO Requirements for Photochemical Activation

2.0K
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
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Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization
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超分子基光启动器用于空间分辨率聚合.

Alex S Loch1, Ibram Mikhail1, Simona Bianco1

  • 1School of Chemistry, University of Glasgow, Glasgow G12 8QQ, U.K.

ACS applied materials & interfaces
|May 12, 2025
PubMed
概括

研究人员开发了一种使用自组装超分子材料控制聚合的新方法. 这种技术局部化了光启动器,增强了机械性能,并使复杂结构的制造成为可能.

关键词:
基烯 (Benzophenone) 是一种含有基的化合物.材料化学 材料化学米塞尔 (Micelle) 是一个小女孩.照片发起人 照片发起人光聚合的光聚合方式.软材料 软材料 软材料超分子凝面条

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科学领域:

  • 聚合物化学 聚合物化学
  • 材料科学 材料科学 材料科学
  • 超分子化学 超分子化学

背景情况:

  • 索衍生物是UV诱导聚合的常见光启动剂.
  • 目前的空间控制方法,如光罩,是自上而下的,可以限制.
  • 局部聚合提供了先进材料制造的潜力.

研究的目的:

  • 开发一种使用超分子材料进行聚合的空间控制的替代方法.
  • 为了研究使用基功能化二作为局部光启动剂.
  • 探索具有可调节性质的机械坚固结构的制造.

主要方法:

  • 利用基功能化二酸形成超分子凝面条.
  • 在凝面模板周围采用了烯酸单体聚合物.
  • 使用粘度和小角度X射线散射 (SAXS) 测量进行了自我组装的特征.
  • 研究了凝面形成的特定结构要求 (例如,4BPAcFF).

主要成果:

  • 在超分子凝面条周围实现局部聚合.
  • 将聚合材料的模数增加了多达两个数量级.
  • 制造的机械坚固和可操作的聚合物结构.
  • 确定了4BPAcFF作为一种成功的凝面形成的超分子光发起剂.
  • 展示了创建复杂设计的能力,包括空心结构.

结论:

  • 高分子凝面作为局部光启动的有效模板.
  • 这种方法提供了对聚合物的精确控制,提高了材料的性能.
  • 该方法允许制造具有可调整机械性能的复杂聚合物架构.