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Videos de Conceptos Relacionados

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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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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Polymers: Defining Molecular Weight01:01

Polymers: Defining Molecular Weight

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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...
3.7K
Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

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Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
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Step-Growth Polymerization: Overview01:03

Step-Growth Polymerization: Overview

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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...
4.3K
Polymer Classification: Architecture01:14

Polymer Classification: Architecture

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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...
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Depolymerizable Olefinic Polymers Based on Fused-Ring Cyclooctene Monomers
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Peso molecular de poliéster cíclico controlado por temperatura en la polimerización por expansión de anillos

Jinxing Jiang1, Ge Yao2, Yaqin Cui1

  • 1Key Laboratory of Advanced Optoelectronic Functional Materials of Gansu Province, Key Laboratory for New Molecule Materials Design and Function of Gansu Universities, College of Chemical Engineering and Technology, Tianshui Normal University, Tianshui 741001, China.

Journal of the American Chemical Society
|October 2, 2025
PubMed
Resumen

Este estudio demuestra un control preciso de los pesos moleculares cíclicos del poliéster mediante el ajuste de la temperatura de polimerización. Este método permite la síntesis ajustable de poli (glicólido de fenilo salicílico) con altas temperaturas de transición al vidrio.

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Área de la Ciencia:

  • Química de los polímeros
  • Ciencias de los materiales

Sus antecedentes:

  • La síntesis de poliésteres cíclicos a través de la polimerización de expansión de anillo es un desafío, particularmente en el control del peso molecular.
  • El control preciso del peso molecular es crucial para adaptar las propiedades del polímero.

Objetivo del estudio:

  • Desarrollar un método para controlar fácilmente el peso molecular de los poliésteres cíclicos.
  • Investigar la relación entre la temperatura de polimerización y el control del peso molecular.
  • Para sintetizar poli (fenil glicólido salicílico) con pesos moleculares ajustables y altas temperaturas de transición al vidrio.

Principales métodos:

  • Se empleó la polimerización por crecimiento en cadena de ésteres cíclicos.
  • Se ajustó la temperatura de polimerización para regular las tasas de polimerización y ciclización.
  • Los pesos moleculares se caracterizaron utilizando cromatografía por permeación de gel, espectrometría de masas y microscopía de fuerza atómica.

Principales resultados:

  • Los pesos moleculares de poli (fenil glicólido salicílico) fueron controlados con éxito, desde 32,2 hasta 189,0 kg/ mol.
  • Se observó una relación inversa entre el logaritmo natural de los pesos moleculares y las temperaturas de polimerización.
  • La temperatura de transición de vidrio alcanzó los 116,6 °C debido a la incorporación del grupo fenilo.

Conclusiones:

  • El ajuste de la temperatura de polimerización ofrece una estrategia efectiva para controlar los pesos moleculares cíclicos de poliéster.
  • Este enfoque facilita la síntesis de poliésteres cíclicos a medida con propiedades térmicas deseables.