Nitroxide mediated synthesis of low dispersity random copolymers for low-loss optical waveguides

Abstract

Candidate materials for low-loss optical waveguides based on poly(glycidyl methacrylate-ran-pentafluostyrene) [P(GMA-ran-PFS)] copolymers were synthesized by nitroxide mediated polymerization (NMP) initiated with BlocBuilder® [N-(2-methylpropyl)-N-(1-diethlphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl) hydroxylamine] bearing a succinimidyl ester group (NHS-BlocBuilder) at 90 °C in 1,4 dioxane. The copolymerizations yielded copolymers with low dispersity Mw/Mn between 1.2 and 1.4. The core structure of single-mode channel waveguides was fabricated by direct UV lithographic patterning. The copolymers with low Mw/Mn resulted in line width roughness (LWR) of about 0.16 μm, whereas LWR of copolymers with Mw/Mn=3.5 but similar compositions was about 0.5 μm. The improvement in microstructural control allotted by NMP permitted finer pattern replication for copolymers desired for optical waveguides, as suggested for photoresist polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2970–2978