Synthesis and characterization of partly fluorinated poly(phthalazinone ether)s crosslinked by allyl group for passive optical waveguides

It is necessary to introduce cross-linkable groups onto polymer chains as the processability and thermal stability of the polymers for passive waveguide device applications are very dependent on their cross-linking capabilities. Herein a series of novel cross-linkable allyl-containing fluorinated poly(phthalazinone ether)s (Allyl-FPPEs) have been prepared by a modified polycondensation of 4-(4-hydroxylphenyl)(2H)-phthalazin-1-one (DHPZ), decafluorobiphenyl (DFBP), 4,4′-(hexafluoroisopropylidene)diphenol (6F-BPA), and 3,3′-diallyl-4,4′-dihydroxybiphenyl (DA-DHBP) for optical waveguide applications. The obtained random polymers were characterized by FT-IR, NMR and GPC. The resulting polymers having good solubility in polar organic solvents at room temperature, can be easily spin-coated into thin films with attracting optical quality, good thermal stabilities (the temperatures of 1% mass-loss after curing: 455-503 °C), and high glass transition temperatures (T_gs: 167-251 °C) which could further increase by about 20 °C after thermal cross-linking. The crosslinked polymer films exhibit good optical properties. By adjusting the feed ratio of the reactants, the refractive indices of TE and TM modes (at 1550 nm) could be well controlled in the range of 1.4998-1.5618 and 1.4954-1.5520, respectively. The optical losses of the crosslinked polymers possess rather low values, less than 0.3 dB/cm at 1550 nm.