Modulating Solubility and Enhancing Reactivity of Photo-Cross-Linkable Poly(styrene sulfonyl azide-alt-maleic anhydride) Thin Films

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• 作者：Dustin W. Janes ; Michael J. Maher ; Gregory T. Carroll ; David M. Saylor ; Christopher J. Ellison
• 刊名：Macromolecules
• 出版年：2015
• 出版时间：November 24, 2015
• 年：2015
• 卷：48
• 期：22
• 页码：8361-8368
• 全文大小：498K
• ISSN：1520-5835

文摘

To formalize our understanding of indiscriminate grafting chemistries as they pertain to cross-linkable polymers and emerging patterning technologies, we designed a new polymer, poly(styrene sulfonyl azide-alt-maleic anhydride) (PSSMA). By modulating its solubility, it can be deposited into smooth, ultrathin films atop polar and nonpolar polymers. Upon heating above 120 掳C or exposure to UV light, highly reactive nitrene intermediates are generated from the azide groups which form covalent adducts and cross-link the PSSMA. Azide photolysis and polymer gelation were studied in the context of a statistical model to gain insight into the network outcomes of nitrenes in a polymer film. For every azide group converted to a nitrene in ambient atmosphere, it has an 11% likelihood of grafting to another chain and a 5% chance of causing a scission. These values can be increased over 3-fold by reducing the O₂ content by 85%. Alternatively, the effects of quenching by ground-state O₂ can be mitigated by adding Michler鈥檚 ketone (MK) to the film. PSSMA/MK blend films possess a 39% (卤13) likelihood for grafting and 29% (卤10) for scission. The higher ratio of scission to grafting is a consequence of the sensitized azides producing triplet-state nitrenes, which favor hydrogen abstraction. These broadly generalizable considerations will be useful to others who wish to maximize light sensitivity in related polymer systems.