Crosslinkable fluorinated poly(arylene ethers) bearing phenyl ethynyl moiety for low-loss polymer optical waveguide devices

Crosslinkable fluorinated poly(arylene ethers) (FPAE-Fn-PEP) with high transparency and high thermal stability have been investigated for low-loss optical waveguide materials. FPAE-Fn-PEP bearing phenyl ethynyl moiety at the polymer chain end were synthesized by the reaction of 4,4′-(hexafluoro-isopropylidene)diphenol with an excess decafluorobiphenyl, followed by the reaction of 4-phenyl ethynyl phenol. The M_ns and M_w/M_ns of the polymers determined by GPC with polystyrene standard were in the range of 6200 to 19,400 and 1.4 to 2.04, respectively. The resulting polymers were thermally crosslinked at 320°C for 2 h. The cured polymers show good chemical resistance and high thermal stability up to 510°C under nitrogen. The refractive indices of their films were controlled between 1.495 and 1.530 at 1.55 μm by adjusting molecular weight. A single-mode channel waveguide made of FPAE-F20-PEP was fabricated by conventional photolithography and O₂ reactive ion etching (RIE). The propagation loss of the channel waveguide was measured and found to be less than 0.2 dB/cm at 1.55 μm. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2881–2887, 1998