Styrene-maleic anhydride copolymer (SMA) with controlled molecular weight (Mn) and narrow dispersity was prepared by RAFT polymerization. The effect of reaction time on monomer conversion was investigated, and the conversion of monomer could achieve 99.1% after 24 h at the temperature of 55 °C. The synthesized SMA was characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC). The result demonstrated that the polymerization of SMA was well controlled and the dispersity (Đ) of SMA was lower than 1.20. Furthermore, SMA copolymers with narrow dispersity and well-regulated Mn (denoted SMA1500, SMA3000, SMA5000, SMA8000, and SMA15800, respectively) were obtained by adjusting the molar ratio of monomer to the chain transfer agent. Moreover, the synthesized SMA was hydrolyzed in NaOH aqueous solution. Then the dispersion of TiO2 in aqueous solution by the hydrolyzed SMA and SZ40005 (the industrial product) were studied. The agglomerate size, the viscosity and the fluidity of TiO2 slurry were tested. The results show that the performance of dispersity for TiO2 in water by SMA prepared via RAFT was better than that of SZ40005. It was found that the viscosity of the TiO2 slurry dispersed by SMA5000 was the lowest among the SMA copolymers tested, and the viscosity value of the TiO2 slurry with a pigment loading of 75% was only 76.6 cp.
A novel method for RAFT copolymerization of styrene (St) and maleic anhydride (MAh) at ambient temperature using ascorbic acid (Asc) as an initiator is reported. Various experimental conditions including reaction component, monomer composition, the amount of Asc, and temperature were investigated in terms of monomer conversion, molecular weight, and molecular weight distribution. In this system, the copolymer of styrene/maleic anhydride (SMA) with well-regulated molecular weight and low molecular weight distribution (Mw/Mn=1.30) was obtained, and the conversion of monomer was 70.4% after 12 hours at 25°C. The NMR spectra demonstrated that the copolymer synthesized possesses a strictly alternating structure. Furthermore, the proposed mechanism adapted to the RAFT copolymerization of St and MAh initiated by Asc at ambient temperature is presented. Using this new methodology, it is possible to achieve well-defined SMA under mild conditions by RAFT copolymerization.
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