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

Abstract

Polymeric optical devices are attracting increasing interest in the field of photonics because of the very appealing performances as structures for both propagating and modulating light signals according to the properties of the employed organic materials. This paper reports the preparation and characterization of low-loss polymer waveguides fabricated from chlorinated copolymers by photochemical crosslinking. A novel monomer derived from reaction between glycidyl methacrylate (GMA) and the chromophore Disperse Red 19 (DR19) was prepared and successfully copolymerized with GMA and chlorostyrene (CS) to obtain the dye-modified copolymer. The latter was crosslinked by photoinitiated polymerization of the pendant epoxy groups, to obtain stable polymeric waveguides. It was found that the major 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 showed increased thermal stability for the copolymer containing DR19. m-line spectroscopy was used to measure the refractive index at 632.8nm. 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.