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相关概念视频

Polymer Classification: Crystallinity01:21

Polymer Classification: Crystallinity

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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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Molecular Weight of Step-Growth Polymers01:08

Molecular Weight of Step-Growth Polymers

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Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
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Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism01:21

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Polymorphism refers to the existence of a drug substance in multiple crystalline forms, known as polymorphs. Recently, this term has been expanded to include solvates (forms containing a solvent), amorphous forms (non-crystalline forms), and desolvated solvates (forms from which the solvent has been removed).
Some polymorphic crystals possess lower aqueous solubility than their amorphous counterparts, leading to incomplete absorption. For instance, the oral suspension of Chloramphenicol, which...
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Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

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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.
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库尔库明多态体的散体阶段的热行为和局部结构组织:分子动力学模拟分析.

Artem Shagurin1,2,3, Michael G Kiselev3, Pal Jedlovszky4

  • 1CNRS UMR 8516 - LASIRe - Laboratoire Avancé de Spectroscopie pour les Interactions la Réactivité et l'environnement, University of Lille, Lille 59000, France.

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概括

黄素 (CUR) 多态性是由分子构成和包装驱动的. 分子动力学模拟显示了多态特异的热行为和稳定性,冷却导致无形状态,而不是再结晶.

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科学领域:

  • 固态化学 固态化学
  • 计算材料科学 计算材料科学
  • 分子动力学模拟的模拟.

背景情况:

  • 黄素 (CUR) 是一种生物活性化合物,以其多态性而闻名.
  • 独特的晶体形式的CUR表现出独特的结构和热物理性质.
  • 了解这些特性对于控制其相位过渡至关重要.

研究的目的:

  • 通过分子动力学模拟,研究CUR在散装阶段的热行为,局部结构组织和多态特异稳定性.
  • 评估和完善经典力场,以准确模拟CUR.
  • 阐明CUR多态行为中的分子构造,包装和相互作用之间的相互作用.

主要方法:

  • 用分子动力学 (MD) 模拟来研究批量CUR.
  • 对实验数据进行了四种经典力场 (OPLS-AA,CGENFF,GAFF2,GROMOS) 的评估.
  • 通过使用DFT数据对二面角的有针对性的再参数化来改进力场.
  • 分析了局部密度,对相互作用,键和分子方向等结构可观测值.

主要成果:

  • 在精制后,OPLS-AA力场准确地复制了实验点和形状分布.
  • 观察到,合规过渡,包装重组和波动在聚态特异性温度附近发生合作.
  • 破坏 π-π 堆叠被确定为格子变化的早期指标.
  • 冷却模拟导致无形CUR状态,表明没有再结晶.

结论:

  • 分子构造,包装和定向相互作用极大地影响了CUR的多态行为.
  • 这项研究为像CUR.这样的柔性分子固体中的相变提供了机械的理解.
  • 精细的模拟模型为控制CUR固态特性提供了基础.