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Types of Step-Growth Polymers: Polyesters01:20

Types of Step-Growth Polymers: Polyesters

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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...
2.5K
Step-Growth Polymerization: Overview01:03

Step-Growth Polymerization: Overview

4.2K
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...
4.2K
Polymer Classification: Architecture01:14

Polymer Classification: Architecture

3.6K
Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
3.6K
Anionic Chain-Growth Polymerization: Mechanism01:04

Anionic Chain-Growth Polymerization: Mechanism

2.4K
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...
2.4K
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)00:53

Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)

2.2K
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
2.2K
Ziegler–Natta Chain-Growth Polymerization: Overview01:17

Ziegler–Natta Chain-Growth Polymerization: Overview

3.8K
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta...
3.8K

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Video Experimental Relacionado

Updated: Dec 30, 2025

Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning
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Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning

Published on: April 16, 2018

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Polímeros degradables con compuestos mecánicos

Yangju Lin1, Tatiana B Kouznetsova1, Stephen L Craig1

  • 1Department of Chemistry , Duke University , Durham , North Carolina 27708 , United States.

Journal of the American Chemical Society
|January 16, 2020
PubMed
Resumen
Este resumen es generado por máquina.

Este estudio introduce un nuevo diseño de polímero que evita la degradación prematura al requerir tanto fuerza mecánica como desencadenantes ácidos para la descomposición. Esta estrategia de doble activación mejora la estabilidad del polímero durante el almacenamiento y el uso.

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Microwave-assisted Functionalization of Polyethylene glycol and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation
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Microwave-assisted Functionalization of Polyethylene glycol and On-resin Peptides for Use in Chain Polymerizations and Hydrogel Formation
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Área de la Ciencia:

  • Química de los polímeros
  • Ciencias de los materiales
  • Mecanoquímica

Sus antecedentes:

  • Los polímeros convencionales persisten en el medio ambiente, impulsando la demanda de alternativas degradables.
  • Los polímeros degradables a menudo sufren una escisión involuntaria de la columna vertebral, lo que reduce su utilidad.
  • Los polímeros degradables existentes carecen de un control robusto sobre los desencadenantes de la degradación.

Objetivo del estudio:

  • Desarrollar un sistema de polímeros con mayor estabilidad frente a la degradación prematura.
  • Implementar un mecanismo de degradación de doble disparador utilizando fuerza mecánica y ácido.
  • Para crear un sistema "AND gate" donde ambos estímulos son necesarios para la escisión de la columna vertebral del polímero.

Principales métodos:

  • Incorporación de un mecanóforo de ciclobutano (CB) como puerta mecánica.
  • Integración de un cetal sensible al ácido con CB en el esqueleto del polímero.
  • Utilizando ultrasonidos para fuerza mecánica y tratamiento ácido para estudios de degradación.
  • Utilizando la espectroscopia de fuerza de molécula única (SMFS) para cuantificar la fuerza de activación mecánica.

Principales resultados:

  • El polímero permanece intacto bajo el disparador ácido solo o la fuerza mecánica solo (limitando MW a 28 kDa).
  • El tratamiento secuencial (ultrasonido seguido de ácido) produce una degradación significativa (disminución de 11 veces hasta 2,5 kDa).
  • La activación del mecanóforo CB requiere aproximadamente 2 nN de fuerza en una escala de tiempo de 100 ms.

Conclusiones:

  • La estrategia "AND gate" evita efectivamente la degradación no deseada del polímero.
  • Este sistema de degradación controlada ofrece una estabilidad mejorada y propiedades adaptadas al final de la vida útil.
  • Los hallazgos allanan el camino para polímeros degradables más duraderos y respetuosos con el medio ambiente.