Synthesis and characterization of large diameter acrylic polymer light conduits

Abstract

In this study, both thermosetting and thermoplastic acrylic polymer light conduits (PLCs) with a diameter of around 8 mm were synthesized in a FEP tube by a thermal polymerization. The composition of A _x B _y C _z was used for the preparation of the polymer core. Here, methyl methacrylate (MMA) and butyl acrylate (BA) were used as the A and B components, respectively, while poly(ethylene glycol 400 diacrylate) (PEGDA-400) or isobornyl methacrylate (IBMA) was used for the C component. The glass transition temperatures of the prepared PLC cores are in the range of –33 to 118 °C by the adjustment of polymer composition. The numerical apertures of the prepared PLCs can be as high as 0.678. The scattering loss due to structural imperfections probably accounted for most of the optical loss in the prepared large diameter PLCs. The peak maxima of the optical loss spectra in the wavelength range of 450–780 nm are in satisfactory agreement with the theoretical calculation from the FTIR spectra. They are due to the fifth harmonic and sixth harmonics of the C–H stretching vibration band. The peak maximum shifts to a higher wavelength on increasing the BA composition in PLCs. The optical loss at peak maxima can be correlated with the C–H bonding density. Hence, the optical windows of the prepared PLCs can be adjusted by polymer compositions. The thermal stability of the prepared thermosetting PLCs was much better than that of the thermoplastic PLCs for optical applications.