Starting from commercially‐available, polymer‐based reactive resins like acrylates or unsaturated polyesters, a systematic investigation was carried out as to the influence organic dopants like phenanthrene and its derivatives have on the optical and thermal properties of the mixtures resulting from curing to the final thermoplastic polymer. The refractive index of PMMA at 633 nm can be increased, starting from 1.49 for the pure polymer, up to a value of around 1.55, and, in the case of the polyester, from 1.565 up to 1.6. The transmittance in the visible range is slightly affected at a lower dopant concentration of up to 10 wt.‐%, and remains better than 80% for a sample with a thickness of 1 mm, in the range between 500 and 800 nm. An unwanted side‐effect of larger dopant concentrations is to lower the glass transition temperature significantly.magnified image

With respect to the realization of new polymer optical devices with enhanced functionality there is a need for the development of new highly transparent polymer based systems with adjustable viscosity prior to curing and tailored refractive index as well as high continuous operation temperature after solidification. The use of phenanthrene as dopant enabled the increase of the refractive index in polymethylmethacrylate from 1.49 up to 1.55(at 589 nm). A copolymerization of a dimethacrylate with the initial methylmethacrylate/polymethylmethacrylate reactive resin suppressed the dopant-related plasticizing effect. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40194.

For modern applications in microoptics, the refractive index (n) of polymers can be adjusted in a certain range by the addition of electron-rich organic dopants. As an unwanted side effect, a pronounced plasticizing occurs. In this work, the addition of a crosslinker (divinylbenzene) to an unsaturated polyester matrix, doped with phenanthrene for n adjustment, allowed us to successfully suppress the plasticizing effect measured after polymerization. Even at high phenanthrene concentrations, the glasstransition temperature of the initial polymer could be almost retained. An increase of the polymer n from 1.5684 to a value of 1.6425 was achieved.

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In microsystem technology, four important material classes are established either for the generation or the replication of microstructured surfaces: silicon, polymers, metals and ceramics. Composite materials consisting of a polymer matrix and ceramic fillers show improved thermomechanical properties in comparison to polymers and can be introduced as a new additional material class. The substitution of micro-sized ceramic fillers by nano-sized ceramics in composites has a strong influence on the composite's physical properties: the reduction of ceramic particle size down to the nanometre scale results in an improved sinter activity owing to the large surface area. The fabrication of dense ceramics is simplified and can be used for a rapid prototyping of microstructured ceramic parts. The addition of nano-sized ceramics with particle sizes of <40 nm to polymers allows the manufacturing of transparent polymer based composites with modified refractive indices for use in polymer waveguides. The influence of the ceramic particle size, the ceramic content and different dispersion methods on the composite's physical properties are discussed.

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Polymer optical components like waveguides or lenses are gaining more and importance as passive or active devices enabling the formation of a sensor and detector platform, e.g. for monitoring the health of large area functional surfaces, which are difficult to access like the wings of an off-shore wind energy plant. With respect to low-loss waveguiding and the use of chemical and mechanical stable polymers there is a need to tailor the optical as well as the thermomechanical properties. The given approach describes the addition of electron-rich small organic molecules like phenanthrene to a poly(methyl methacrylate)-based polymer matrix enabling a significant refractive index increase from 1.49 up to almost 1.55 (@589 nm). As undesirable side effects the optical transmittance in the visible range at higher guest molecule content is reduced, and a pronounced plasticizing occurs. Both hamper the application of the mixture, e.g. as optical waveguide material. The plasticizing and the accompanied drop of the glass transition temperature, determining the maximum operation temperature, can be partially compensated by the copolymerization of the methyl methacrylate monomer (MMA) with the difunctional monomer ethyleneglycol dimethacrylate (EGDMA) at certain crosslinker content. The resulting new developed guest-host mixtures enable the realization of optical devices with adjusted rheological behavior prior to curing and tailored optical properties after polymerization.

With respect to the fabrication of metal parts carrying surface relief microstructures using composite reaction molding as a rapid prototyping variant of micrometal injection molding, the influence of microsized iron powder on the viscosity of different unsaturated polyester resins applied as polymer binder has been investigated systematically. The initial binder viscosity determines the viscosity of the composite and hence the accessible critical filler load. A further dilution of the unsaturated polyester resin with styrene allows a significant increase of the filler load at constant shear rate and temperature from 36 up to 57 vol% iron content. A successful estimation of the critical filler load using different established empirical models initially developed for ceramic‐filled solutions or dispersions is possible. A pronounced flow activation energy increase at high iron loads was also observed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers