Influence of the grafting process on the orientation and the reactivity of azide-terminated monolayers onto silica surface
Résumé
Click chemistry is widely used in materials and surface science for its high efficiency, ease of use and high yields.
Azide-terminated SAMs have been prepared successfully by using three different deposition methods (postfunctionalization
and direct grafting by immersion as well as spin coating). Strikingly, our study shows that the
reactivity of the azido group on the surface with the alkyne in solution is not trivial and seems to be closely
related to the orientation of the azide. Indeed, more the azide is vertically oriented more it is accessible and
reactive. The orientation of azido dipoles at the surface depends strongly on the method used to prepare the
monolayer. The post-functionalization method allows to have a homogeneous population of the azide groups on
the surface with a better vertical orientation than that obtained using direct grafting by immersion or spin
coating processes. Whatever the type of azide-terminated SAMs, the reactivity of the accessible vertical azido
groups is complete. This study clearly demonstrates that it is possible to control the amount of reactive azides
and, consequently, the amount of molecules immobilized on the surface after the click reaction by choosing the
deposition method
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