Crosslinkable polymers for optical waveguide devices. II. Fluorinated ether ketone oligomers bearing ethynyl group at the chain end

Fluorinated ether ketone oligomers bearing a crosslinkable ethynyl group at the chain end have been investigated for low-loss polymer optical waveguid e devices. These oligomers are designed to achieve low birefringence and we re synthesized by the reaction of 4,4'-(hexafluoroisopropylidene)diphenol w ith an excess decafluorobenzophenone, followed by reaction with (phenylethy nyl)phenol or ethynylphenol. The molecular weights (M(n)s) and polydispersi ties of the oligomers determined by GPC with polystyrene standard are in th e range of 6600-8500 g/mol and 1.79-2.04, respectively. By spin coating and thermal crosslinking, the polymer solutions easily provide the good optica l quality thin films. The cured films show good chemical resistance and hig h thermal stability up to 460 degrees C under nitrogen. At 1.55 mu m wavele ngth, the refractive index and birefringence of the films show in the range of 1.5104-1.5172 and 0.0078-0.0014, respectively. The propagation loss of the single-mode channel waveguide was measured to be less than 0.5 dB/cm at 1.55 mu m. (C) 1999 John Wiley & Sons, Inc.