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Molecular Weight of Step-Growth Polymers

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...

Polymers: Molecular Weight Distribution

Polymers: Molecular Weight Distribution

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.

Laminar Flow

Laminar Flow

Laminar flow represents a smooth, orderly fluid motion where particles move along parallel paths, resulting in minimal mixing between layers. Streamlined particle paths characterize this flow regime and occur under conditions where viscous forces dominate over inertial forces. The distinction between laminar, transitional, and turbulent flow is primarily determined by the Reynolds number, a dimensionless quantity calculated as:

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Characterizing Dissipative Elastic Metamaterials Produced by Additive Manufacturing

Characterizing Dissipative Elastic Metamaterials Produced by Additive Manufacturing

Published on: June 28, 2024

Maximum Dissipation Reduction in Bulk Polymeric Turbulence.

Yi-Bao Zhang^1,2, Feng Wang¹, Sheng-Hong Peng¹

¹Northwestern Polytechnical University, Institute of Extreme Mechanics, School of Aeronautics, National Key Laboratory of Aircraft Configuration Design, Key Laboratory for Extreme Mechanics of Aircraft of Ministry of Industry and Information Technology, Xi'an 710072, China.

Physical Review Letters

|October 25, 2025

Summary

This summary is machine-generated.

Polymer additives in turbulent fluids create two regimes: dissipation reduction and maximum dissipation reduction (MDR). The MDR regime, characterized by sheetlike vortices, occurs when polymer effects reach the integral length scale.

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Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

Published on: February 22, 2018

Area of Science:

Fluid Dynamics
Polymer Physics
Turbulence Research

Background:

Polymeric turbulence involves complex interactions between fluid flow and polymer additives.
Understanding energy dissipation and vortex structures is crucial for characterizing these flows.

Purpose of the Study:

To experimentally investigate flow regimes and vortex structures in bulk polymeric turbulence.
To identify the conditions leading to maximum dissipation reduction (MDR) and characterize the associated flow structures.

Main Methods:

High-resolution, three-dimensional velocity measurements were employed.
Analysis focused on polymer concentration effects on energy dissipation and vortex dynamics.

Main Results:

Two distinct regimes of polymer effect on energy dissipation were identified: dissipation reduction and MDR.
The MDR regime was found to occur when polymer-affected scales reach the integral length scale, not the Lumley scale.
Sheetlike vortex and strain structures dominate in the MDR regime, stabilizing shear layers.

Conclusions:

The MDR regime represents a universal flow state in bulk polymeric turbulence.
Findings provide a phase diagram for polymeric turbulence and insights into viscoelastic fluid flow regimes.
Sheetlike vortex structures are significant in MDR, aiding prediction of flow behavior.