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Related Concept Videos

Polymer Classification: Architecture01:14

Polymer Classification: Architecture

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...
Radical Chain-Growth Polymerization: Chain Branching01:17

Radical Chain-Growth Polymerization: Chain Branching

The skeletal structure of polymers synthesized via radical polymerization is always branched. For example, the polymerization of ethylene by radical polymerization results in a low-density grade of polyethylene with a heavily branched skeletal structure. Here, the radical site abstracts hydrogen from the growing chain, and the radical site shifts from the end (a primary carbon center) to anywhere within the growing chain (a secondary carbon center). Consequently, the part of the chain from the...
Olefin Metathesis Polymerization: Overview01:13

Olefin Metathesis Polymerization: Overview

Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene01:17

Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene

The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.
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.
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,...

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Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
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Entanglement transition in hyperbranched polyether-polyols.

Christoph Tonhauser1, Daniel Wilms, Yasmin Korth

  • 1Institute of Organic Chemistry, Organic and Macromolecular Chemistry, Duesbergweg 10-14, Johannes Gutenberg-University Mainz, D-55099 Mainz, Germany.

Macromolecular Rapid Communications
|May 14, 2011
PubMed
Summary
This summary is machine-generated.

Hyperbranched polymers, specifically hyperbranched polyglycerol, demonstrate entanglement dynamics above a critical molecular weight. This finding addresses the long-standing question of whether these complex polymer architectures can form entanglements.

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Area of Science:

  • Polymer Science
  • Rheology
  • Materials Science

Background:

  • Hyperbranched polymers possess unique architectures with numerous branching points.
  • Understanding their viscoelastic properties is crucial for predicting material behavior and applications.
  • The potential for entanglement in hyperbranched polymers remains an open question in polymer physics.

Purpose of the Study:

  • To investigate the viscoelastic properties of hyperbranched polyglycerol (hbPG).
  • To determine if hbPG can form entanglements and identify the critical molecular weight for entanglement.
  • To correlate viscoelastic behavior with molecular architecture and molar mass.

Main Methods:

  • Synthesis of hbPG with varying molecular weights (600–106,000 g·mol⁻¹) and narrow polydispersities (1.2–1.8) via anionic ring-opening polymerization.
  • Rheological characterization to study viscoelastic properties, including zero shear viscosity.
  • Analysis of scaling behavior and identification of a critical molar mass for entanglement.

Main Results:

  • At low molecular weights, classical scaling behavior of viscosity with molecular weight was observed.
  • A plateau-like viscosity region was identified between 3,000 and 10,000 g·mol⁻¹.
  • Entanglement dynamics were indicated above a critical molar mass (Mc* ≈ 20,000 g·mol⁻¹).

Conclusions:

  • Hyperbranched polyglycerols are capable of forming entanglements.
  • A critical molar mass exists beyond which entanglement significantly influences viscoelastic properties.
  • The study provides key insights into the rheological behavior of branched polymer architectures.