Reactivity, neutralized, strong-acid monomers

The reactivity of the neutralized, strong-acid monomers [e.g., sodium styrenesulfonate (32) and 2-sulfoethyl methacrylate (30)] with nonionic monomers also is dependent on the changes in polarity of the system (i.e., dielectric constant, solvation, and hydration) and with solution pH (Table IV for the sodium styrenesulfonate studies). The effect also is evident (39) in the copolymerization of two ionogenic monomers, acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, with different pK values. For acrylic acid, the reactivity ratio is 0.740 0.13 at pH 7 and 1.58 0.15 at pH 2-4. For 2-acrylamido-2-methylpropanesulfonic acid, the reactivity ratio was 0.187 0.09 at pH 7 and 0.111 0.03 at pH 2-4. These studies (39)... 

From these observations, it seemed possible to be able to control the reactivity of ionizing monomers in general by proper control of solution pH. Thus, in the case of the copolymerization of AMPS, a strong acid, with AA, a weaker acid, three distinct regimes exist - the all acid system (very low pH), sodium AMPS with acrylic acid (pH 2-4), and the fully neutralized system at high pH. 

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