单个灵活的多电解质分子在贫弱溶剂中的线圈-球体形状转换的级联
Anton Kiriy1, Ganna Gorodyska, Sergiy Minko
1Institut für Polymerforschung Dresden, Hohe Strasse 6, Germany.
Journal of the American Chemical Society
|November 7, 2002
概括
在上吸附的疏水性多电解质揭示了随着离子强度的增加而发生的形状变化. 这些灵活的分子从线圈转变为紧的球体,形成独特的"珍珠项链"结构.
科学领域:
- 聚合物科学 聚合物科学
- 表面化学 表面化学
- 生物物理学的生物物理.
背景情况:
- 多电解质表现出由离子强度和表面相互作用影响的复杂行为.
- 了解单分子构造对于聚合物物理学和材料科学至关重要.
- 在表面上的吸附可以改变与溶液相比的聚合物行为.
研究的目的:
- 为了研究吸附的疏水性多电解质的构造转变.
- 在不同的离子强度下,将单分子结构与溶液构成相关联.
- 为了阐明聚电解质在表面上的相变机制.
主要方法:
- 原子力显微镜 (AFM) 用于单分子成像.
- 在上吸附聚2-乙烯二和聚甲基化二甲基基乙烯二甲基化.
- 溶液离子强度的系统变化.
主要成果:
- 吸附的多电解质采用反映其溶液状态的形状.
- 增加的离子强度触发了从长长的线圈到紧的球体的过渡.
- 观察到中间的"珍珠项链"结构,具有不同的珠子大小和数量.
- 证据表明第一阶段类型的相位过渡是由多个形状的共存表明.
结论:
- 疏水性多电解质在吸附时经历离子强度依赖的形状变化.
- 观察到的结构为链内分离和相位过渡提供了洞察力.
- AFM是一种强大的工具,可用于可视化单分子聚合物在表面上的行为.
相关概念视频
Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
Induced Electric Dipoles
A permanent electric dipole orients itself along an external electric field. This rotation can be quantified by defining the potential energy because the external torque does work in rotating it. Then, the potential energy is minimum at the parallel configuration and maximum at the antiparallel configuration. While the former is a stable equilibrium, the latter is an unstable equilibrium.
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
Ion Exchange
Ion exchange chromatography separates charged molecules from a solution by reversibly exchanging them with mobile, or 'active', ions associated with the oppositely charged stationary phase. This method can be used to separate ions, soften and deionize water, and purify solutions. The polymers comprising the ion-exchange column are high-molecular-weight and chemically stable polymers, crosslinked to be porous and essentially insoluble. They are also functionalized with either acidic or basic...
The 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...
The Colloidal State
The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...


