pH-Responsive Photoluminescence Properties of a Water-Soluble Copolymer Containing Quinoline Groups in Aqueous Solution

The synthesis of a water-soluble copolymer containing quinoline groups, P(DMAM-co-SDPQ), through free radical copolymerization of N,N-dimethylacrylamide, DMAM, with 2,4-diphenyl-6-(4-vinylphenyl) quinoline, SDPQ, is presented and the optical properties of the final product are investigated in aqueous solution as a function of pH. It is found that the emission peak of SDPQ is red-shifted from 411 to 484 nm with decreasing pH, due to the protonation of quinoline groups at low pH, suggesting that this copolymer may function as a luminescent pH-indicator. Moreover, the copolymer exhibits the characteristics of a luminescent pH-detector within the pH range 2 < pH < 4, as in this pH region the ratio of the emission intensity at 411 nm over that at 484 nm changes linearly in a logarithmic scale with the pH of the solution. Finally, the formation of less polar quinoline clusters in the aqueous P(DMAM-co-SDPQ) solution upon increasing pH was detected through Nile red probing. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2078-2083, 2010