A water-soluble fluorescent copolymer poly(acrylamide-acrylic acid-styrene pyridinium) (PAAS) for detecting polymer concentration in real time was synthesized via micellar free-radical polymerization by acrylamide, acrylic acid, and styryl-pyridinium salt derivative (SP-4). The special Donor-π-Acceptor unit and ionic structure of SP-4 endued the copolymer with excellent fluorescent properties and remarkable water solubility. The fluorescent copolymer was fully characterized by Fourier transform infrared, 1 H nuclear magnetic resonance, thermogravimetry, Ubbelohde viscosity, ultraviolet-visible spectroscopy, and fluorescence measurements. Furthermore, the fluorescence intensity and the concentration of PAAS were verified to have ideal linear relationship with a correlation coefficient up to 0.9993, indicating that the copolymer's concentration can be easily measured by detecting its fluorescence intensity. Most importantly, the introduction of water-soluble fluorescent monomer SP-4 endowed the PAAS with good fluorescent stability in a wide range of temperature, pH, and brine concentrations. This study demonstrated that the fluorescent copolymer PAAS exhibits great potential application in detecting polymer concentration in various environments.
Trans-4-[p-(N,N-diethyl) amino-styryl]-N-allyl pyridinium bromide (SP-2). Yield 50%. 1 H NMR (400 MHz, CDCl 3 ) δ: 8.74 (d, J = 6.4 Hz, 2H), 7.84 (d, J = 5.1 Hz, 2H), 7.63 (d, J = 15.8 Hz, 1H), 7.49 (d, J = 7.2 Hz, 2H), 6.80 (d, J = 15.7 Hz, 1H), 6.62 (d, J = 7.2 Hz, 2H), 6.01(m, 1H), 5.46 (d, J = 17.6 Hz, 1H), 5.42 (d, J = 10.8 Hz, 1H), 5.28 (d, J = 5.4 Hz, 2H), 3.38 (t, 4H), 1.16 (q, J = 5.2 Hz, 6H). MS [ESI-time of flight (TOF)] calcd for [C 20 H 25 N 2 ] + [M-Br] + 293.2012, found 293.2009. Trans-4-[p-(N,N-dibutyl) amino-styryl]-N-allyl pyridinium bromide (SP-4). Yield 55%. 1 H NMR (400 MHz, CDCl 3 ) δ: 8.85 (d, J = 6.4 Hz, 2H), 7.79 (d, J = 6.5 Hz, 2H), 7.56 (d, J = 15.9 Hz, 1H), 7.47 (d, J = 8.4 Hz, 2H), 6.78 (d, J = 15.8 Hz, 1H), 6.59 (d, J = 8.5 Hz, 2H), 6.00 (m, J = 16.6, 11.3, 6.5 Hz, 1H), 5.48 (d, J = 17.0 Hz, 1H), 5.41 (d, J = 10.1 Hz, 1H), 5.30 (d, J = 6.4 Hz, 2H), 3.28 (t, J = 7.8 Hz, 4H), 1.53 (m, J = 7.6 Hz, 4H), 1.30 (m, J = 7.4 Hz, 4H), 0.92 (q, 6H). MS (ESI-TOF) calcd for [C 24 H 33 N 2 ] + [M-Br] + 349.2638, found 349.2616. Trans-4-[p-(N,N-dihexyl) amino-styryl]-N-allyl pyridinium bromide (SP-6). Yield 39%. 1 H NMR (400 MHz, CDCl 3 ) δ: 8.85 (d, J = 6.5 Hz, 2H), 7.76 (d, J = 6.5 Hz, 2H), 7.55 (d, J = 15.8 Hz, 1H), 7.47 (d, J = 8.5 Hz, 2H), 6.78 (d, J = 15.8 Hz, 1H), 6.60 (d, J = 8.6 Hz, 2H), 6.02 (m, J = 16.5, 10.6, 5.7 Hz, 1H), 5.49 (d, Scheme 2. The synthesis of fluorescent monomers SP-n.
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