Waveguides made of poly-methyl-methacrylate (PMMA) play a major role in the homogeneous distribution of display backlights as a matrix for solid-state dye lasers and polymer optical fibers (POFs). PMMA is favored because of its transparency in the visible spectrum, low price, and well-controlled processability. Nevertheless, technical drawbacks, such as its limited temperature stability, call for new materials. In this work, the copolymerization technique is used to modify the properties of the corresponding homopolymers. The analytical investigation of fourteen copolymers made of methyl-methacrylate (MMA) or ethyl-methacrylate (EMA) as the basis monomer is summarized. Their polymerization behaviors are examined by NMR spectroscopy with subsequent copolymerization parameter evaluation according to Fineman-Ross and Kelen-Tüdös. Therefore, some r-parameter sets are shown to be capable of copolymerizations with very high conversions. The first applications as high-temperature resistant (HT) materials for HT-POFs are presented. Copolymers containing isobornyl-methacrylate (IBMA) as the comonomer are well-suited for this demanding application.
Integrating highly efficient luminescent dyes into poly(methyl methacrylate) matrices with well-defined parameters, such as degree of polymerization and dispersity, is a key step in the development of emerging technologies such as fiber-based solar collectors, sensors, contactless coupling devices and integrated light sources. In this work, four perylene-based fluorescent dyes, perylene from Sigma-Aldrich, Lumogen F Yellow 083 from BASF, Perylene Orange from TCI and Lumogen F Red 300 from BASF, were polymerized in bulk with methyl methacrylate. The molecular weight distribution was controlled by the ratio between the chain transfer agent and initiator and was measured by size exclusion chromatography. A dopant-dependent increase in the degree of polymerization, in which the dye causes a drop in the concentration of active growing polymer chains, was observed. Spectroscopic online monitoring of the process in transmission mode confirmed this observation and indicated the formation of stable perylene radicals during the polymerization. Comparative experiments with fluorescent (metal) organic dyes did not show a similar effect. Fitting models for the dye-dependent molecular weights for Lumogen Yellow and Lumogen Red are proposed.
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