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相关概念视频

Asymmetric Lipid Bilayer01:35

Asymmetric Lipid Bilayer

Biological membranes show uneven distribution of different types of lipids in the inner and outer layers, resulting in transverse asymmetric membranes. The treatment of the erythrocyte membrane with the enzyme phospholipase confirmed the asymmetric nature of the lipid bilayer. The enzyme hydrolyzes lipids into fatty acids and hydrophilic groups. The phospholipase acts only on the outer layer of the membrane, while the inner layer remains intact. The phospholipase treatment resulted in 80%...
Anionic Chain-Growth Polymerization: Overview01:20

Anionic Chain-Growth Polymerization: Overview

The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
Molecular Weight of Step-Growth Polymers01:08

Molecular Weight of Step-Growth Polymers

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...
Types of Step-Growth Polymers: Polyesters01:20

Types of Step-Growth Polymers: Polyesters

The introduction of polyesters has brought major development to the textile industry. The wrinkle-free behavior of polyester blends has eliminated the need for starching and ironing clothes.
Polyesters are commonly prepared from terephthalic acid and ethylene glycol; the crude product is known as poly(ethylene terephthalate) or PET. However, polyesters are synthesized industrially by transesterification of dimethyl terephthalate with ethylene glycol at 150 °C. The two reactants and the polymer...
Step-Growth Polymerization: Overview01:03

Step-Growth Polymerization: Overview

Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
Many natural and synthetic polymers are produced by...
Anionic Chain-Growth Polymerization: Mechanism01:04

Anionic Chain-Growth Polymerization: Mechanism

The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael acceptor.

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相关实验视频

Updated: May 11, 2026

Density Gradient Multilayered Polymerization (DGMP): A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering
12:54

Density Gradient Multilayered Polymerization (DGMP): A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering

Published on: February 12, 2013

在多电解质多层中不对称的增长.

Ramy A Ghostine1, Marie Z Markarian, Joseph B Schlenoff

  • 1Department of Chemistry and Biochemistry, The Florida State University, Tallahassee, Florida 32306-4390, USA.

Journal of the American Chemical Society
|May 16, 2013
PubMed
概括
此摘要是机器生成的。

研究人员发现,在多重电解质多层中常见的电荷过度补偿模型是不正确的. 这项研究揭示了聚二甲基化物 (PDADMAC) 和聚硫酸 (PSS) 薄膜中的不对称生长和复杂形成.

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10:43

Single-Molecule Diffusion and Assembly on Polymer-Crowded Lipid Membranes

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Density Gradient Multilayered Polymerization (DGMP): A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering
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Density Gradient Multilayered Polymerization (DGMP): A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering

Published on: February 12, 2013

Fabrication of Large-area Free-standing Ultrathin Polymer Films
10:08

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科学领域:

  • 聚合物科学 聚合物科学
  • 材料科学 材料科学 材料科学
  • 表面化学 表面化学

背景情况:

  • 聚电解质多层 (PEMs) 在各种应用中广泛使用.
  • PEMs的组装通常被描述为负荷过度补偿的模型.
  • 研究的特定系统涉及到聚二甲基化物 (PDADMAC) 和聚乙烯硫酸盐 (PSS).

研究的目的:

  • 调查PDADMAC/PSS多层聚电解质多层内部的电荷分布和组装机制.
  • 在PEM形成中挑战传统的费用过度补偿模式.
  • 开发一种新的模型,解释PEMs观察到的增长和结构.

主要方法:

  • 利用放射性计量器来量化阳性与阴性聚合物单位的比例.
  • 在多电解质多层中分析了电荷分布.
  • 开发了一种反应-扩散模型来描述观察到的不对称增长.

主要成果:

  • 对于每个层的收费过度补偿的公认模型被发现是不正确的.
  • 过度补偿仅在添加聚酸 (PDADMAC) 时才发生;聚酸 (PSS) 仅仅是补偿.
  • 观察到不对称的生长,在几层后积累过多的正电荷,导致明显的玻璃和复杂区域.

结论:

  • 组装的PDADMAC/PSS PEM表现出不对称的增长和复杂的形成,偏离简单的电荷过度补偿模型.
  • 一个新的反应-扩散模型准确地描述了不同的固态度和充电丰富层的形成.
  • 了解这种不对称的增长对于预测和控制PEM特性至关重要.