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Published on: May 21, 2019
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Triphenylsulfonium topophotochemistry.
E Despagnet-Ayoub1, W W Kramer, W Sattler
1Beckman Institute, California Institute of Technology, Pasadena, California 91125, USA. despagne@caltech.edu.
Summary
Photodegradation of triphenylsulfonium nonaflate (TPS) in PMMA films yields novel photoproducts. In-cage reactions are crucial for forming triphenylene and dibenzothiophene, highlighting the importance of polymer matrix effects.
Area of Science:
- Photochemistry
- Polymer Science
- Organic Chemistry
Background:
- Triphenylsulfonium salts are widely used as photoacid generators in photolithography.
- Understanding the photoproducts of these materials is crucial for optimizing lithographic processes.
- The behavior of triphenylsulfonium nonaflate (TPS) within a polymer matrix like poly(methyl methacrylate) (PMMA) under irradiation requires detailed investigation.
Purpose of the Study:
- To characterize the photoproducts formed from 193 nm irradiation of TPS embedded in PMMA films.
- To elucidate the reaction mechanisms leading to the formation of these photoproducts.
- To investigate the role of the polymer matrix and topochemical factors in TPS photochemistry.
Main Methods:
- Photochemical irradiation of TPS/PMMA films at 193 nm.
- Chromatographic analysis: High-Performance Liquid Chromatography (HPLC), Gel Permeation Chromatography (GPC), Gas Chromatography-Mass Spectrometry (GC-MS).
- Spectroscopic analysis: UV-visible spectroscopy, Nuclear Magnetic Resonance (NMR) including Diffusion Ordered Spectroscopy (DOSY-NMR).
Main Results:
- Two previously unreported photoproducts, triphenylene and dibenzothiophene, were identified.
- GPC and DOSY-NMR indicated incorporation of TPS fragments into the PMMA polymer matrix.
- Irradiation in solution yielded only trace amounts of these products, suggesting matrix confinement is critical.
Conclusions:
- The formation of triphenylene and dibenzothiophene from TPS in PMMA is primarily due to in-cage, secondary photochemical reactions.
- Topochemical factors within the polymer matrix significantly influence the photoproduct distribution.
- The study provides insights into the complex photochemistry of sulfonium salts in polymer films, relevant for advanced material applications.
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