Copolymerization of Methacrylic Acid and N-Vinylpyrrolidone in Aqueous Solution |
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Authors: | S Ponratnam S Prabhakara Rao S G Joshi S L Kapur |
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Institution: | National Chemical Laboratory , Poona, 8, India |
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Abstract: | The monomer reactivity ratios for the copolymerization of methacrylic acid (MA) and N-vinylpyrrolidone (NVP) in aqueous media at 30°C were determined as a function of pH (range 2-10), by use of both the modified differential (YBR) and integrated copolymerization equation to process the data at high conversions (< 70% by weight). The reactivity ratio r1 (for MA) ranges from 0.92 to 8.3 and that for NVP (r2) is very small except at pH 7 and 8. The ri values show two minima: 2.9 at pH 4 and 0.92 at pH 8, nearly corresponding to the pKa values of the monomer MA and the polymer, respectively. Addition of 1 M sodium chloride results in an increase of n values, and the values are still lower than those of the undissoeiated acid. The trend of rxwith pH is seen to follow that of the homopolymerization behavior of MA reported in the literature. The r1 and r2 are of the same order as those obtained in dimethylformamide in the literature. |
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