Oxygen Tolerance during Surface-Initiated Photo-ATRP: Tips and Tricks for Making Brushes under Environmental Conditions

Achieving tolerance toward oxygen during surface-initiatedreversibledeactivation radical polymerization (SI-RDRP) holds the potentialto translate the fabrication of polymer brush-coatings into upscalableand technologically relevant processes for functionalizing materials.While focusing on surface-initiated photoinduced atom transfer radicalpolymerization (SI-photoATRP), we demonstrate that a judicious tuningof the composition of reaction mixtures and the adjustment of thepolymerization setup enable to maximize the compatibility of thisgrafting technique toward environmental conditions. Typically, thepresence of O-2 in the polymerization medium limits theattainable thickness of polymer brushes and causes the occurrenceof "edge effects", i.e., areas at thesubstrates' edges where continuous oxygen diffusion from thesurrounding environment inhibits brush growth. However, the concentrationsof the Cu-based catalyst and "free" alkyl halide initiatorin solution emerge as key parameters to achieve a more efficient consumptionof oxygen and yield uniform and thick brushes, even for polymerizationmixtures that are more exposed to air. Precise variation of reactionconditions thus allows us to identify those variables that becomedeterminants for making the synthesis of brushes more tolerant towardoxygen,and consequently more practical and upscalable.