Exploiting NIR Light-Mediated Surface-Initiated PhotoRAFT Polymerization for Orthogonal Control Polymer Brushes and Facile Postmodification of Complex Architecture through Opaque Barriers

Abstract

An oxygen-tolerant SI-PhotoRAFT technique has been developed for the efficient synthesis of surface-tethered polymer brushes under low-energy near-infrared (NIR) light. This technique takes advantage of the unique properties of NIR light, in particular enhanced penetration, to effectively prepare polymeric coatings, even through barriers that are opaque to visible light. The NIR-mediated SI-PhotoRAFT polymerization technique was utilized to precisely modulate brush height in direct correlation with the irradiation time. Additionally, this technique facilitated sequential chain extension, enabling the fabrication of block copolymer brushes. Moreover, the incorporation of a photoresponsive monomer, 7-[4-(trifluoromethyl)coumarin]acrylamide [2-(2-oxo-4-(trifluoromethyl)-2H-chromen-7-yl)acrylamide, TCAm], within the poly(N,N-dimethylacrylamide) brushes enables orthogonal control over polymerization and cross-linking processes through the use of two different wavelengths (NIR and UV light). When exposed to a UV source (λ = 365 nm, 18.2 mW/cm²), the TCAm undergoes dimerization triggering cross-linking of the grafted brush “arms”. Furthermore, by utilizing the enhanced penetration of NIR light, a polymeric coating was prepared on the inner walls of a tube that was opaque to visible light. Finally, this process is successfully applied to the synthesis of antifouling surfaces on poly(dimethylsiloxane)-coated silicon wafers, leading to inhibition of biofouling.