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Related Concept Videos

Fast Reactions01:27

Fast Reactions

Fast reactions occurring in times shorter than the time needed to mix reactants pose a unique challenge for investigation. In a liquid-phase continuous-flow system, reactants A and B are swiftly pushed into the mixing chamber, where mixing occurs within 1 ms. The reaction mixture then flows through an observation tube, and one measures light absorption to determine species concentrations at various points of the tube. This method is most appropriate when relatively large volumes of reactants...
Measuring Reaction Rates03:09

Measuring Reaction Rates

Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical reaction. Optically active substances have the capability of rotating the plane of polarization of linearly polarized light passing through them—a feature called optical rotation. Optical activity is attributed to the molecular structure of substances. Normal monochromatic light is unpolarized and possesses oscillations of the electrical field in...
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...
Polymers02:34

Polymers

The word polymer is derived from the Greek words “poly” which means “many” and “mer” which means “parts”. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the properties that they exhibit. Additionally,...
Radical Chain-Growth Polymerization: Mechanism01:09

Radical Chain-Growth Polymerization: Mechanism

The radical chain-growth polymerization mechanism consists of three steps: initiation, propagation, and termination of polymerization. The polymerization initiates when a free radical generated from the radical initiator adds to the unsaturated bond in the monomer. The unpaired electron of the free radical and one π electron in the unsaturated bond creates a σ bond between the free radical and the monomer. As a result, the other π electron in the unsaturated bond converts this species into the...
Free-Radical Chain Reaction and Polymerization of Alkenes02:35

Free-Radical Chain Reaction and Polymerization of Alkenes

The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.

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Related Experiment Video

Updated: Jul 12, 2026

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization
07:28

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Published on: November 27, 2015

Simultaneous studies of reaction kinetics and structure development in polymer processing.

W Bras, G E Derbyshire, D Bogg

    Science (New York, N.Y.)
    |February 17, 1995
    PubMed
    Summary

    This study used advanced techniques to observe polymer structure formation during processing. Thermodynamics of phase separation, not hydrogen bonding, drives structure development in polyurethanes.

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    Published on: November 27, 2015

    Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example
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    Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
    06:55

    Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

    Published on: September 26, 2016

    Area of Science:

    • Polymer Science
    • Materials Science
    • Physical Chemistry

    Background:

    • Understanding polymer structure development is crucial for controlling material properties.
    • Polyurethanes exhibit complex structures influenced by processing conditions.
    • Simultaneous kinetic and structural analysis offers insights into polymer formation.

    Purpose of the Study:

    • To investigate the driving forces behind structure development in segmented block copolyurethanes during processing.
    • To correlate structure evolution with reaction kinetics using advanced analytical methods.
    • To elucidate the fundamental mechanisms governing polyurethane morphology.

    Main Methods:

    • Utilized time-resolved synchrotron radiation small-angle X-ray scattering (SR-SAXS) for structural analysis.
    • Employed Fourier-transform infrared spectroscopy (FTIR) for monitoring reaction kinetics.
    • Applied a combined SR-SAXS and FTIR approach to model segmented block copolyurethanes.

    Main Results:

    • Confirmed that thermodynamics of phase separation is the primary driver for structure development.
    • Demonstrated that hydrogen bonding plays a secondary role compared to phase separation.
    • Provided time-resolved data linking processing to final polymer morphology.

    Conclusions:

    • The thermodynamic drive of phase separation dictates polyurethane structure formation.
    • Kinetic and structural studies are essential for understanding polymer processing.
    • This methodology advances the comprehension of structure-property relationships in polyurethanes.