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Conformational Transition of the Copolymer of Maleic Acid and α-Methylstyrene in Aqueous Solution

The pH-induced conformational transition of an alternating copolymer of maleic acid and α-methylstyrene in aqueous NaCl solutions has been investigated by pH-titration, optical, viscometric, and dilatometric measurements. The relation between the intrinsic viscosity and the degree of dissociation of the primary carboxyl group shows a transition from a compact to an extended coil form. The volume change accompanying the transition at 0.009 M NaCl was found to increase from −0.8 cm3 to 2.2 cm3 per monomole with increasing temperature from 15 to 35°C. All results are compared with those of the maleic acid copolymer with styrene studied previously, and the influence of methyl groups on the transition is discussed.