ma5b01875_si_001.pdf (2.21 MB)
Modulating Solubility and Enhancing Reactivity of Photo-Cross-Linkable Poly(styrene sulfonyl azide-alt-maleic anhydride) Thin Films
journal contributionposted on 2015-11-24, 00:00 authored by Dustin W. Janes, Michael J. Maher, Gregory T. Carroll, David M. Saylor, Christopher J. Ellison
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 °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’s ketone (MK) to the film. PSSMA/MK blend films possess a 39% (±13) likelihood for grafting and 29% (±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.
ambient atmospherenetwork outcomesform covalent adductsfavor hydrogen abstractionPSSMApolymer gelationnonpolar polymersreactive nitrene intermediatesAzide photolysisultrathin filmsModulating SolubilityMKO 2 contentThin FilmsTopatterning technologiesgain insightpolymer filmpolymer systemsazide grouplight sensitivityscissionazide groupsEnhancing ReactivityUV lightgeneralizable considerations