WATER-SOLUBLE COPOLYMERS .35. PHOTOPHYSICAL AND RHEOLOGICAL STUDIES OF THE COPOLYMER OF METHACRYLIC-ACID WITH 2-(1-NAPHTHYLACETYL)ETHYL ACRYLATE

Fluorescence and dilute solution viscosity behavior of a 20:80 mol % copolymer of 2-(l-naphthylacetyl)ethyl acrylate (NAEA) and methacrylic acid (MAA), respectively, have been studied. The fluorescence spectra of this copolymer showed an almost 4-fold increase in excimer emission relative to monomer emission (IE/IM) upon increasing from pH 5 to 9. Similarly, as the pH of the medium increases, reduced viscosity increases, indicating a transition from a compact coil to a more expanded coil at pH 7.5. This behavior is unlike that previously reported presumably due to the extent of naphthyl group substitution, the hydrophobic character of both the naphthyl groups and the pendant methyl groups of MAA, and effective decoupling of the chromophore from the polymer backbone by a spacer group. The effects of urea, a water-structure breaker, and of polymer concentration indicate that, at high pH, NAEA-MAA forms an intramolecular “hypercoil”. High quenching efficiencies of both monomer and excimer fluorescence by copper(II) ions result from ionic binding of the quencher ions with the copolymer. © 1990, American Chemical Society. All rights reserved.