相关概念视频
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.
01:17Thermal 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.
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
01:06Interfacial Electrochemical Methods: Overview
Interfacial electrochemical methods focus on the phenomena occurring at the boundary between an electrode and a solution, as opposed to bulk methods that concentrate on the solution's overall properties. These interfacial methods are classified as either static or dynamic based on the presence of a nonzero current in the electrochemical cell and the consistency of analyte concentrations. Static methods, such as potentiometry, measure the cell's potential without any significant current passing...
01:28Ionic Association
The ionic association is the association of oppositely charged ions in an electrolyte solution to form ion pairs. Bjerrum defined ion pairs as two oppositely charged ions whose electrostatic attraction exceeds the thermal energy of the system, typically expressed as 2kT. Electrostatic attraction depends on ionic charge, separation distance, and the dielectric constant of the medium. Thermal energy, represented by kT, reflects the tendency of ions to move independently due to molecular motion.
01:30The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
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聚乙烯离子体的电化学表征和聚电解质介导的电化学,用于不同合的合聚合物之间的接口.
Mark C Lonergan1, Calvin H Cheng, Brandi L Langsdorf
1Department of Chemistry and The Materials Science Institute, University of Oregon, Eugene, Oregon 97403, USA.
Journal of the American Chemical Society
|January 24, 2002
概括
本研究描述了两种功能化的聚乙烯类似物,用于在合聚合物中创建接口. 聚离子电解质能够精确控制兴奋剂,促进制造不同兴奋的聚合物接口用于电子应用.
科学领域:
- 结合聚合物的电化学.
- 对于有机电子的材料科学.
- 聚合物科学与工程 聚合物科学与工程
背景情况:
- 结合聚合物之间的接口对于有机电子非常重要,类似于基于的微电子.
- 控制合聚合物的兴奋剂对于制造功能界面至关重要.
- 现有的方法在实现精确的兴奋剂控制和接口制造方面面临挑战.
研究的目的:
- 在电化学上表征聚四甲基二环氧化四乙烯乙醇硫酸盐 (P(A)) 和聚二环氧化四乙烯乙醇三甲基三甲硫酸盐 (P(C)).
- 开发一种电化学方法,用于制造不同合的合聚合物之间的接口.
- 探索聚离子电解质在合离子体中用于受控的氧化还原化学.
主要方法:
- 循环电压测量用于描述不同电解质系统中的P (A) 和P (C) 的兴奋剂行为.
- 电化学石英晶体微平衡 (EQCM) 用于监测在兴奋剂期间的离子交换.
- 实验使用了标准电解质 (Me4NBF4/CH3CN) 和一个聚离子支持电解质 (四甲聚) /CH3CN).
主要成果:
- P(C) 显示了n型和p型的兴奋剂,而P(A) 仅显示了p型的兴奋剂.
- 确定了P(C) 的n-doping和P(C) /P(A) 的p-doping的明显形式潜力.
- 聚离子电解质使P (A) 的自限氧化,选择性兴奋剂和P (C) 中再氧化的抑制成为可能.
结论:
- 该研究展示了一种方法,用于制造不同的合聚合物之间的接口,使用聚电解质介导电化学.
- 聚离子电解质可以精确控制离子补偿,从而使结合聚合物具有量身定制的氧化还原特性.
- 这种方法有望促进有机电子设备的发展.