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Radical Chain-Growth Polymerization: Mechanism

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...

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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...

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The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the generated carbocation,...

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Related Experiment Video

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

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Rhythmic Conformational Change in a SinglePolymer Chain Induced by Laser Irradiation.

Journal of Biological Physics

|January 25, 2013

Summary

We observed a single polymer chain (T4DNA) rhythmically switching between folded and elongated states. This oscillation, driven by a laser, involves energy dissipation and limit-cycle dynamics.

Keywords:

dissipation structure folding phase-transition in a single polymer chain limit-cycle oscillation under thermal fluctuations optical tweezers thermodynamically open conditions time-dependent Ginzburg-Landau equation (TDGL)

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Area of Science:

Polymer physics
Biophysics
Optical trapping

Background:

Understanding polymer dynamics is crucial in various scientific fields.
Investigating single polymer behavior provides fundamental insights into material properties.

Purpose of the Study:

To investigate the rhythmic conformational changes of a single polymer chain (T4DNA).
To explore the dynamics of polymer folding and elongation under specific conditions.
To analyze the role of laser-induced temperature gradients in polymer behavior.

Main Methods:

Utilized a focused continuous wave (cw) Nd:YAG laser beam (1064 nm) for polymer trapping and temperature gradient creation.
Studied a single T4DNA polymer chain (166 kbp, 56 μm contour length).
Analyzed the conformational transitions between folded and elongated states under thermodynamically open conditions.

Main Results:

Observed a rhythmic conformational change between folded and elongated states in the T4DNA polymer.
Demonstrated the dual role of the laser in trapping the polymer and establishing a temperature gradient.
Characterized the oscillatory phenomenon as a limit-cycle oscillation.

Conclusions:

The study reveals a novel oscillatory behavior in a single polymer chain driven by laser manipulation.
Photon energy dissipation is a key factor in the observed limit-cycle oscillation.
This work offers new perspectives on controlling and understanding polymer dynamics using light.