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Preparation of Light-responsive Membranes by a Combined Surface Grafting and Postmodification Process
Published on: March 21, 2014
Controlled nitroxide-mediated styrene surface graft polymerization with atmospheric plasma surface activation.
1Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095-1592, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 22, 2008
Summary
Controlled nitroxide-mediated graft polymerization (NMGP) via atmospheric pressure plasma-induced polymerization (APPI-NMGP) offers superior polystyrene grafting on silicon surfaces compared to free radical graft polymerization (FRGP). APPI-NMGP yields smoother, more uniform polymer layers with higher surface coverage.
Area of Science:
- Materials Science
- Polymer Chemistry
- Surface Science
Background:
- Surface modification of silicon is crucial for advanced material applications.
- Graft polymerization techniques like free radical graft polymerization (FRGP) and nitroxide-mediated graft polymerization (NMGP) are used for polymer layer growth.
- Atmospheric pressure plasma (APP) offers a versatile tool for surface activation and polymerization initiation.
Purpose of the Study:
- To investigate and compare polymer layer growth on silicon using atmospheric pressure plasma-induced free radical graft polymerization (APPI-FRGP) and controlled nitroxide-mediated graft polymerization (APPI-NMGP).
- To evaluate the surface morphology, thickness, and homogeneity of polystyrene layers formed by both methods.
- To determine the optimal conditions for achieving high-quality grafted polymer layers with low surface roughness.
Main Methods:
- Silicon surfaces were activated using atmospheric pressure hydrogen plasma.
- Polystyrene was grafted onto activated silicon using both APPI-FRGP and APPI-NMGP (with TEMPO).
- Kinetic studies were performed by varying monomer concentration, temperature, and initiator/mediator concentrations.
- Atomic force microscopy (AFM) was used to analyze surface roughness and morphology.
Main Results:
- APPI-FRGP showed a maximum grafted layer thickness of 125 Å at 2.62 M monomer concentration and 85°C, with increased roughness at higher temperatures.
- APPI-NMGP demonstrated linear growth and a greater thickness (285 Å after 60 h) under optimized conditions (10 mM TEMPO, 4.36 M monomer, 120°C).
- APPI-NMGP resulted in polystyrene-grafted surfaces with high homogeneity and low root-mean-square (RMS) roughness (0.36 nm), comparable to native silicon (0.21 nm).
Conclusions:
- Atmospheric pressure plasma-induced controlled radical polymerization, specifically APPI-NMGP, is effective for creating high-quality grafted polymer layers on silicon.
- APPI-NMGP offers significant advantages over APPI-FRGP, including reduced uncontrolled polymerization and improved control over film properties.
- The developed APPI-NMGP method enables the formation of grafted polymer layers with lower surface roughness and higher surface coverage, suitable for advanced applications.
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