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相关概念视频

Characteristics and Nomenclature of Copolymers01:24

Characteristics and Nomenclature of Copolymers

2.4K
Copolymers are the products obtained from the polymerization of multiple monomer species. So, in a polymer chain itself, there can be multiple repeating units that come from different monomers. The process of synthesizing a polymer from different monomer species is called copolymerization. When two monomers are involved, the polymer is known as a bipolymer. Polymers with three and four monomers are termed terpolymers and quaterpolymers, respectively. Figure 1 depicts the copolymerization of...
2.4K
Polymers: Molecular Weight Distribution01:10

Polymers: Molecular Weight Distribution

3.2K
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.
3.2K
Molecular Weight of Step-Growth Polymers01:08

Molecular Weight of Step-Growth Polymers

2.1K
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...
2.1K
Cationic Chain-Growth Polymerization: Mechanism00:57

Cationic Chain-Growth Polymerization: Mechanism

2.2K
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
2.2K
Mechanical Protein Functions01:58

Mechanical Protein Functions

4.9K
Proteins perform many mechanical functions in a cell. These proteins can be classified into two general categories- proteins that generate mechanical forces and proteins that are subjected to mechanical forces. Proteins providing mechanical support to the structure of the cell, such as keratin, are subjected to mechanical force, whereas proteins involved in cell movement and transport of molecules across cell membranes, such as an ion pump, are examples of generating mechanical force. 
4.9K
Polymer Classification: Stereospecificity01:26

Polymer Classification: Stereospecificity

2.3K
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
2.3K

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相关实验视频

Updated: May 16, 2025

Engineering Molecular Recognition with Bio-mimetic Polymers on Single Walled Carbon Nanotubes
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Engineering Molecular Recognition with Bio-mimetic Polymers on Single Walled Carbon Nanotubes

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揭示机械化学力分布与多机械块共聚合物.

Vittal Bhat1, Yan Xia1

  • 1Department of Chemistry, Stanford University, Stanford, California 94305, United States.

ACS macro letters
|May 14, 2025
PubMed
概括

聚合物机械化学的力量比以前想象的要远得多. 通过调整聚合物块长度,科学家甚至可以在链条末端激活机械,为聚合物科学揭示了新的可能性.

科学领域:

  • 聚合物科学 聚合物科学
  • 机械化学 机械化学
  • 材料科学 材料科学 材料科学

背景情况:

  • 聚合物机械化学经常使用超声波进行研究.
  • 力量分布通常以以聚合物链为中心的抛物线为模型.
  • 对聚合物链末端施加力的程度尚未完全理解.

研究的目的:

  • 在聚合物链沿着定义的位置研究机械化学反应性,特别是对终端.
  • 了解机械孔位置和聚合物链长度对机械激活的影响.
  • 克服合成挑战,为此类研究准备聚合物.

主要方法:

  • 使用活环开放元解聚合物合成块共聚合物的合成.
  • 纳入一个梯级类型的机械孔和norbornene.
  • 控制块的位置和长度.

主要成果:

  • 终端机械孔块的激活程度低于DP ≈1000的聚合物中心块.
  • 延长惰性块的长度显著增加了终端机械孔块的激活 (DP ≈200).
  • 终端块在诱导期后实现了与中央块相似的激活.

结论:

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Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers
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Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers

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Using Polystyrene-block-polyacrylic acid-coated Metal Nanoparticles as Monomers for Their Homo- and Co-polymerization
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Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers
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Synthesis of Monodisperse Cylindrical Nanoparticles via Crystallization-driven Self-assembly of Biodegradable Block Copolymers

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  • 超声波下的力量在聚合物链上覆盖了广泛的范围.
  • 高度的机械化学可以远离链中心实现.
  • 这项工作扩大了对聚合物中力分布和机电孔激活的理解.