结合聚合物对氧化反应有增加的排放反应
Eric L Dane1, Sarah B King, Timothy M Swager
1Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Journal of the American Chemical Society
|May 18, 2010
概括
含有铁的聚合物对氧化剂表现出光激活反应,氧化形式显示出增强的量子产量和光稳定性. 这表明了先进的氧化剂传感和排放材料的潜力.
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
- 有机电子 有机电子
背景情况:
- 聚甲乙烯 (PPE) 共聚合物以其光特性而闻名.
- 聚合物中乙烯基组的氧化可以改变其电子和光学特性.
- 了解氧化对光量子产量和寿命的影响对于材料设计至关重要.
研究的目的:
- 为了研究含有乙烯的PPE共聚物在氧化后的光激活反应.
- 阐明光量子产量和寿命观察到的增加背后的机制.
- 探索这些氧化聚合物在传感和光电子学中的潜在应用.
主要方法:
- 合成含有铁的个人防护用品共聚物.
- 对硫氧化物和硫的乙烯替代物的受控氧化.
- 光谱分析 (吸收,发射) 用于评估光学特性变化.
- 测量光量子产量和寿命.
主要成果:
- 选择性氧化乙基到硫氧化物和硫诱导了强烈的光激活反应.
- 氧化导致光量子产量 (Phi ((F)) 和光寿命 (tau ((F)) 的增加,这归因于边界分子轨道的空间重叠和非辐射衰变的减少.
- 与预期相反,硫氧化物并没有始终灭光;光谱变化表明某些氧化共聚合物的供体-接受体相互作用.
- 氧化聚合物在固态中表现出高光量子产量,并提高了光稳定性.
- 在有机溶剂中与氧化催化剂一起观察到对过氧化的开启光反应.
结论:
- 含有thioether的PPE共聚物为开发氧化剂光传感器提供了一个有前途的平台.
- 氧化过程提高了光效率和光稳定性,使这些材料适用于需要强大的光学性能的应用.
- 可调整的可见光谱辐射和高效的光辐射是先进材料潜在应用的关键优势.
相关概念视频
01:26Photochemical Electrocyclic Reactions: Stereochemistry
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
Selection Rules: Photochemical Activation
01:17Oxidation of Phenols to Quinones
In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:32UV–Vis Spectroscopy of Conjugated Systems
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in the...
One of the factors influencing λmax is the extent of conjugation in the...
01:11Aryldiazonium Salts to Azo Dyes: Diazo Coupling
The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the para position.
01:17Thermal Electrocyclic Reactions: Stereochemistry
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.
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.