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Substrate-Independent Approach to Dense Cleavable Polymer Brushes by Nitroxide-Mediated Polymerization
Wei Wei1, A Balamurugan1, Jonathan H Dwyer1
1Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
ACS Macro Letters
|May 25, 2022
Summary
This study demonstrates high-density polymer brushes grown via surface-initiated nitroxide-mediated polymerization (SI-NMP). These dense polystyrene (PS) brushes exhibit enhanced molecular weights compared to free polymers.
Area of Science:
- Polymer Chemistry
- Materials Science
- Surface Science
Background:
- Developing stable initiator layers for surface-initiated polymerization is crucial for controlled polymer growth.
- Nitroxide-mediated polymerization (NMP) offers a controlled radical polymerization technique suitable for creating polymer brushes.
- Achieving high grafting densities is essential for many applications of polymer brushes.
Purpose of the Study:
- To grow high grafting density polymer brushes using surface-initiated nitroxide-mediated polymerization (SI-NMP).
- To create a stable initiator layer for robust polymer brush synthesis.
- To investigate the characteristics of cleaved polymer brushes compared to free polymers.
Main Methods:
- Formation of a cross-linked inimer coating bearing nitroxide-mediated polymerization (NMP) inimers and glycidyl methacrylate (GMA).
- Surface-initiated nitroxide-mediated polymerization (SI-NMP) to grow polystyrene (PS) brushes.
- Utilized a sacrificial layer for cleaving the grown polymer brushes.
- Employed Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) for surface analysis and kinetic studies.
Main Results:
- Achieved exceptionally high grafting densities of polystyrene (PS) brushes, reaching up to 1.12 chains/nm².
- The initiator layer demonstrated stability under prolonged exposure to organic solvents at elevated temperatures.
- Cleaved polymer brushes exhibited higher molecular weights than their free polymer counterparts.
- AFM and XPS analyses provided insights into surface morphology and polymerization kinetics.
Conclusions:
- Successfully synthesized among the densest polystyrene (PS) brushes reported to date using SI-NMP.
- The developed inimer coating provides a stable platform for controlled surface polymerization.
- The method yields polymer brushes with distinct properties compared to free polymers, opening avenues for advanced material design.
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