什么促进了微观秩序:将平均场理论应用于末端
David A King1, Randall D Kamien1
1Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19104, USA.
粒子形状和尾巴长度极大地影响了液晶相位过渡. 圆形的尖端和更长的尾部通过阻碍层间距,破坏阴性相的稳定性来促进形相形成.
科学领域:
- 材料科学 材料科学 材料科学
- 软物质物理学 软物质物理学
- 化学物理 化学物理
背景情况:
- 阴性液晶可以过渡到性阶段,但这种行为取决于粒子.
- 构成粒子的形状,特别是它们的尖端,在确定是否形成质相时起着至关重要的作用.
- 分子结构,例如N-CB分子中基链的长度,也会影响质相形成.
研究的目的:
- 为了研究粒子尖端几何学的关键作用,在nematic-to-smectic阶段过渡.
- 了解分子结构,特别是尾巴的长度,如何影响液晶相位的行为.
- 阐明粒子形状和尾巴长度影响阴性和阴性相稳定的机制.
主要方法:
- 利用简化的二维模型来模拟粒子的行为.
- 模拟的球形圆柱体有圆的尖端为"布巴"和圆体有尖尖的尖端为"基基".
- 代表N-CB分子作为一个核心体,附有聚合物尾巴.
主要成果:
- 圆形的尖端 (球形圆柱体) 促进形阶段的形成,与尖端 (圆体) 不同.
- 较长的聚合物尾巴 (N-CB分子中的N≥8个碳) 对于 smectic 阶段形成至关重要.
- 圆形的尖端和更长的尾巴都减少了层间空间的可访问性,在较低密度下破坏了阴性相的稳定.
结论:
- 颗粒尖的几何是液晶中从内马特转变到斯梅克特转变的关键决定因素.
- 分子设计,结合圆形的尖端和延长的尾巴,可以用来控制液晶相位的行为.
- 这些发现提供了关于软物质系统相变的基本原则的见解.
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