Covalent attachment of chromophores to chlorinated copolymers for optical waveguides: synthesis and optical characterization

Low-loss polymer waveguides fabricated from chlorinated copolymers by photochemical crosslinking were prepared and characterized. A novel monomer derived from reaction between glycidyl methacrylate (GMA) and Disperse Red 19 (DR19) chromophore was prepared and successfully copolymerized with chlorostyrene (CS) to obtain the dye-modified copolymer. The latter was crosslinked by photoinitiated polymerization of the pendant epoxy groups, to obtain stable polymer waveguides. It was found that the predominant product of the reaction between GMA and DR19 was formed through transesterification of the methacrylate with elimination of glycidol, while traces of products deriving from the epoxy ring-opening reaction were detected. The presence of the nitro substituent on DR19 favoured chain transfer reactions during the polymerization reaction, leading to a decrease in the polymerization degree. It was also observed that the presence of grafted DR19 negatively affected the crosslinking reaction, as a lower epoxy group conversion was observed for the modified copolymer. Thermal analysis indicated that the copolymer containing DR19 showed increased thermal stability. m-line spectroscopy was used to measure the refractive index at 632.8 nm. The experimental results confirm that the new class of chlorine-based polymeric materials represent a very attractive proposal in the panorama of materials employed in the fabrication of electro-optical devices for telecommunication applications.