Polymers that crosslink nitrenes

Polymers that Crosslink by Dimerization of Nitrenes and by Other Combinations of Free-Radicals to Form Covalent... 

It is known that aromatic azides are photodecomposed to give active nitrenes as the transient species, which react with the environmental binder polymers to crosslink them. However, the mechanism of these photocrosslinking polymers has not been studied in detail. L.S.Efros et al. have proposed that the rubber polymer is crosslinkes in such a way that the aromatic nitrene inserts into an unsaturated bond of the polymer to give an aziridine ring. The experimental evidence for this, however, has not been given (8). 

Although mononitrenes do not act as crosslinking agents themselves, they can generate unpaired electrons in the polymer chains by the abstraction of hydrogen molecules from the polymer. As the result, the polymer chains are crosslinked by the recombinations of these unpaired electrons. Crosslinking by mononitrene in such a way, depends on the activity of the nitrene and may be not necessarily less efficient in some combination of monoazide with the polymer than that by dinitrene as is seen in the case for... 

Figure 16. Crosslinking reactions in bisarylazide-rubber resists. The primary photoevent is production of a nitrene which then undergoes a variety of reactions that result in covalent, polymer-polymer linkages. A schematic representation of crosslinking via nitrene insertion to form aziridine linkages is shown together with several other reaction modes available to the...

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