Synthesis, characterization, and Pb2+ ion sensing application of hexa-armed dansyl end-capped poly(?-caprolactone) star polymer with phosphazene core

Abstract

Novel hexa-armed dansyl end-capped poly(epsilon-caprolactone) (PCL) star polymer with phosphazene core (P2) was prepared via ring opening polymerization (ROP) and esterification reactions. P2 showed dual fluorescence emission when excited at 328 nm in acetonitrile : water (6 : 4) due to twisted intramolecular charge transfer (TICT) between dimethylamino and naphthalene units in the dansyl moiety. TICT emission band (A band) in the emission spectra red-shifted with increasing solvent polarity. P2 responded to the addition of Pb2+, Hg2+, Co2+, Cd2+, Mn2+, and Zn2+ metal ions by decreasing TICT emission band with slight bathochromic shifts. The highest quenching efficiency was observed for Pb2+ ion with Stern-Volmer constant of 324.74M(-1). The Stern-Volmer plot for Pb2+ was rather linear with the increasing concentration of the quencher, indicating a dynamic (collisional) quenching mechanism. Stern-Volmer constants for Hg2+, Co2+, Cd2+, Mn2+, and Zn2+ ions were found to be 212.33, 189.21, 36.24, 20.84, and 20.69, respectively. Besides, the highest quenching efficiency (94.24%) was attained in the presence of Pb2+, suggesting that P2 could be employed as a potential Pb2+ chemical probe. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42380.