Water-soluble, meta- and para-linked poly(arylene ethynylene)s containing L-aspartic acid-functionalized fluorene units (P1 and P2) and their model compounds (M1 and M2) have been synthesized, and their photophysical properties and fluorescent sensing properties were investigated in aqueous solution. P1 and M1 with the meta-linkage show blue-shifted absorption and emission spectra, and decreased photoluminescence quantum yields compared with those of P2 and M2 with para-linkage. Their absorption and fluorescence spectra are pH dependent perhaps due to the aggregation of the polymer chains at low pH values. In buffer solutions, both polymers and their model compounds exhibit the excellent selectivity and sensitivity to Hg2+ over other common metal ions. Furthermore, the quenching constant and detection limit of P1 are determined to be 1.04 x 10(7) M-1 and 10 nM, and show the higher sensitivity compared to P2. Further comparison of their model compounds reveal that the sensitivity and quenching efficiency of M1 is also higher than that of M2, indicating that the meta-linkage pattern plays a key role in improving their Hg2+ ion sensing properties. In addition, both meta- and para-linked polymers exhibit the higher quenching efficiency than their model compounds due to the amplified fluorescence response of conjugated polymer. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012