UV-Induced Modulation of the Refractive Index and the Surface Properties of Photoreactive Polymers BearingN-Phenylamide Groups

Abstract

Poly(N,N′-diphenyl-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxamide) was prepared as a functional polymer containing photoreactive arylamide groups. Under 254 nm UV irradiation, the arylamide groups undergo a photo-Fries rearrangement which yields aminosubstituted ketones as the reaction product. In thin films of the polymer, the photoreaction leads to a significant increase of the refractive index n by Δn = +0.10 which is unusually large for polymeric materials and more than sufficient for optical applications such as waveguiding. Due to the photogeneration of aminoketone groups, the chemical reactivity of the polymer is also enhanced after the irradiation step. This was employed for a selective postexposure modification of polymer films with acid chlorides and fluorescamine. In combination with photolithographic techniques, a structured surface functionalization was demonstrated. By reaction of the amino groups with bicyclo[2.2.1]hept-5-ene-2-carboxylic acid chloride a polymer surface bearing pendant norbornene units was created. Using the ring opening metathesis polymerization technique (ROMP), the immobilized norbornene moieties were successfully employed in a grafting-from polymerization of norbornene monomers. Photoreactive polymers bearing N-phenylamide groups are of interest for photolithography, optical applications such as waveguiding and holographic data storage, and for site selective surface functionalization.