Investigation of structural properties of melt-spun graded-index polymer optical fibers made from PMMA

The structural properties of PMMA, which has been melt-spun and treated using a specific cooling profile, is investigated in order to evoke desired optical and mechanical properties. Several PMMA fibres, which had been melt spun and subsequently processed with different temperature profiles, were analysed by small-angle X-ray scattering (SAXS) measurements. These results will be compared to a combination of numerical models, which consider the quenching of a filamentary PMMA polymer melt in water. This multi-scale simulation considers macroscopically the cooling process in the water and within the fiber. The spatially resolved cooling rates, which have been simulated at different locations serve as input for a 3D-Monte-Carlo polymer simulation model, which takes, among others, the Lennard-Jones, the bending and bond potentials into account in order to predict the resulting PMMA structure of the fabricated fiber These simulated structures are then evaluated in order to analyse their macroscopic properties. These comprise for instance the polymer entanglement, which describes the interaction of neighboring polymer chains leading to stronger, but stiffer fibers. Entanglement will also affect the glass-transition temperature, which determines the maximum operation temperature. But this can also lead to increased optical scattering, which will be subject to investigations, as well.