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Download fileModulating Solubility and Enhancing Reactivity of Photo-Cross-Linkable Poly(styrene sulfonyl azide-alt-maleic anhydride) Thin Films
journal contribution
posted on 2015-11-24, 00:00 authored by Dustin W. Janes, Michael J. Maher, Gregory
T. Carroll, David M. Saylor, Christopher J. EllisonTo 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.
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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