To open out new aspects of 9,9-diarylfluorene (DAF)-based polymers with high performances, 9,9-(4-hydroxyphenyl)-4,5-diazafluorene (N-BPF) was designed as a new cardo structure and the properties of poly(ether ketone)s (N-PEKs) containing N-BPF skeletons were examined in detail. N-PEKs were synthesized in high yields via polycondensation of N-BPF with difluoroarenes. N-PEKs showed cardo polymer-specific properties such as high thermal stability and high solubility in organic solvents. The addition of p-toluenesulfonic acid (TsOH) to N-PEK resulted in the formation of network polymer based on interchain hydrogen bonds. It turned out that the films of network polymer are flexible and transparent and exhibit high refractive index and low birefringence. The effects of feed ratio of TsOH to N-PEK were also evaluated on the mechanical properties of network polymer. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4541-4549