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相关概念视频

Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

3.7K
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
3.7K
Potential Due to a Polarized Object01:29

Potential Due to a Polarized Object

471
A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...
471
Polymer Classification: Crystallinity01:21

Polymer Classification: Crystallinity

3.1K
Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
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Polymers: Defining Molecular Weight01:01

Polymers: Defining Molecular Weight

3.1K
Unlike small molecules with definite molecular weights, polymers are a mixture of individual polymer chains of varying lengths, each with a unique molecular weight.  So, the molecular weight of a polymer is expressed as an average value based on the average size of the polymer chains. The two most common forms of averages used for polymers are the number average molecular weight and weight average molecular weight.
The number average molecular weight (Mn) is the summation of the number...
3.1K
Van der Waals Interactions01:24

Van der Waals Interactions

66.5K
Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions between particles with permanent, partial, or temporary charges. The intermolecular forces between neutral atoms and molecules are ion–dipole, dipole–dipole, and dispersion forces, collectively known as van der Waals forces.
66.5K
Mean free path and Mean free time01:22

Mean free path and Mean free time

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Consider the gas molecules in a cylinder. They move in a random motion as they collide with each other and change speed and direction. The average of all the path lengths between collisions is known as the "mean free path."
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相关实验视频

Updated: Sep 11, 2025

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
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在固体表面附近的多分散聚合物:分析平均场理论.

A F den Ouden1,2, R Tuinier1,2, M Vis1,2

  • 1Laboratory of Physical Chemistry, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.

The Journal of chemical physics
|August 13, 2025
PubMed
概括

多聚散聚合物的表面特性是由它们的平均链长决定的,而不是分布形状. 较长的聚合物链在表面上吸附更多,这一发现在溶液和化物中一致.

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科学领域:

  • 聚合物物理 聚合物物理
  • 软物质科学是一种软物质科学.
  • 表面化学 表面化学

背景情况:

  • 了解聚合物在接口上的行为对于材料设计至关重要.
  • 聚合物中的多分散性 (不同的链长) 复杂化了理论预测.
  • 现有的模型往往难以准确地描述多散系统的表面特性.

研究的目的:

  • 开发一个理论框架来预测聚散聚合物的表面特性.
  • 为了获得细分密度配置和表面张力的分析表达式.
  • 通过数值和实验数据验证理论预测.

主要方法:

  • 线性平均场理论应用于多分散聚合物系统.
  • 对吸附量和表面张力的代数式的推导.
  • 与数值自相一致的场计算和聚合物化的实验结果进行比较.

主要成果:

  • 表面特性主要由平均聚合度 (N̄) 控制,不论链长分布变异 (σ2).
  • 较长的聚合物链在弱吸附状态下表现出优选吸附.
  • 导出的分析表达式显示了与数值模拟和聚合物化的实验数据的定量一致.

结论:

  • 使用平均链长的简化理论方法准确地预测了多散聚合物的表面特性.
  • 这些发现适用于聚合物溶液和聚合物化物.
  • 这项工作为设计和理解基于聚合物的材料提供了有价值的工具.