Here, we report regioselectively functionalized synthesis, as well as photo physical, electrochemical, and thermal, of a novel water-soluble conjugated polymer. For this purpose, horseradish peroxidase (HRP)-catalyzed polymerization of a multifunctional monomer, 7-amino-4-hydroxy-2-naphthalene sulfonic acid (AHNAPSA) was carried out by using hydrogen peroxide as the oxidant at room temperature for 24 h under air. The structure of poly(7-amino-4-hydroxy-2-naphthalene sulfonic acid), (PAHNAPSA) was identified by using nuclear magnetic resonance, infrared and ultraviolet-visible. Further characterization was performed by means of gel permeation chromatography (GPC), thermogravimetry (TG), differential scanning calorimetry (DSC), cyclic voltammetry (CV), photoluminescence (PL), dynamic light scattering (DLS) and solid state conductivity measurements. The spectral analysis results exhibited functional group selective polymerization of the monomer containing a multi-active center. Solvent effects on the optical, electrochemical and photo physical properties of PAHNAPSA were investigated by using five different solvents. PAHNAPSA presented an irreversible redox characterization at different scan rates. Optical band gap of PAHNAPSA is also found in the range of 3.18 eV to 3.55 eV. The fluorescence measurements were utilized to investigate the photochemical behaviors of PAHNAPSA in selected polar solvents. Accordingly, PAHNAPSA surprisingly presented multicolor emission behavior with relatively high quantum yield in all selected solvents. In addition, PAHNAPSA presented a reversible pH-responsive behavior and also had high selectivity and sensitivity towards chromium ions. Finally, the kinetic parameters associated with the solid state thermal degradation of PAHNAPSA were calculated from isoconversional methods. The TG/DTG analysis showed that PAHNAPSA followed a diffusion controlled degradation mechanism in N-2. (C) 2016 Elsevier B.V. All rights reserved.