Cross-Linkable Highly Fluorinated Poly(Arylene Ether Ketones/Sulfones) for Optical Waveguiding Applications

Novel cross-linkable, highly fluorinated poly(arylene ether ketones/sulfones) have been prepared by copolycondensation reactions of perfluorinated aromatic ketone/sulfone with 4,4‘-(hexafluoroisopropylidene)diphenol and a tetrafluorostyrol-containing bisphenol (i.e., 1,1-bis(4-hydroxyphenyl)ethyl-1-phenyl 2,3,5,6-tetrafluorostyrol ether). The reactions were conducted at low temperature in the presence of calcium hydride and cesium fluoride. The resulting polymers have number-average molecular weights in the range of 25 000−36 000, excellent solubilities in common organic solvents, high glass transition temperatures ( T g ) in the region of 150−185 °C, and good thermal stabilities ( T d up to 480 °C). Tough, flexible, and transparent thin films of these polymers can be readily prepared by both solution casting and spin-coating. By adjusting the feed ratio of monomers, the refractive index and cross-linking density of the polymers can be readily controlled. Cross-linking of these polymers has been demonstrated by both thermal heating and UV irradiation. The cross-linked polymer thin films exhibit low optical loss (∼0.5 dB/cm) and low birefringence (∼2 × 10 - 3 ) at 1550 nm, demonstrating that they are promising candidates for optical waveguide materials.