The dissociation of the two adjacent carboxylic acids in maleic acid‐containing copolymers is expected to differ from those of poly(acrylic acid) and poly(methacrylic acid) where the acids are separated by two carbons on the backbone. In this work, we have employed potentiometric titration and NMR spectroscopy to characterize the dissociation behavior and chemical compositions of several water‐soluble maleic acid‐containing copolymers. A distinct two‐step process corresponding to the dissociation of the two adjacent carboxylic acids is observed in aqueous CaCl2 (0.02 N) solution for copolymers of maleic acid and isobutylene, diisobutylene, and styrene. Such a two‐step ionization process is less recognizable, however, for the copolymers of maleic acid and linear alkenes ranging from n‐hexene to n‐octadecene. Nevertheless, the compositions of all copolymers, including the extent of neutralization and the ratio of the comonomer moieties, are estimated from the titration curves. The chemical composition derived from potentiometry and NMR spectroscopy for all copolymers are approximately 1 : 1 (maleic acid : comonomer). With the exception of the hydrophobically modified copolymer of isobutylene‐maleic acid, no obvious conformational transition was observed over the whole range of ionization for these hydrophobic maleic acid‐containing copolymers. This is related to the aggregated state of these copolymers in aqueous media. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3571–3583, 2004

The dilute solution behavior of several alternating copolymers of maleic acid has been characterized by static and dynamic light scattering, intrinsic viscosity, and pulsed‐gradient spin‐echo NMR spectroscopy. The copolymer of maleic acid–sodium salt and isobutylene (IBMA‐Na, Mw ∼350 kg/mol) dissolves readily in concentrated aqueous salt solutions. Changes in chain dimensions with ionic strength and pH are similar to those of the lesser salt solution‐soluble poly(acrylic acid‐sodium salt). The hydrophobically modified (with n‐butyl, n‐hexyl, n‐octyl, and phenethyl amines) copolymers of maleic acid–sodium salts and isobutylene (IBMA‐NHR‐Na) show no sign of large intermolecular aggregation in 0.1 N sodium acetate (NaAc). However, the sizes of the copolymers are relatively small compared to that of the ionized parent copolymer (IBMA‐Na, Mw ∼350 kg/mol), suggesting intramolecular aggregation of the alkyl side‐chain groups along the polymer backbone. The copolymer modified with the longer chain n‐decyl, on the other hand, forms stable large intermolecular aggregates containing 33 chains/aggregate. The copolymers of maleic acid–sodium salt and styrene (SMA‐Na) appear to have no signs of aggregation, despite being a hydrophobic polyelectrolyte. The copolymer of maleic acid–sodium salt and di‐isobutylene (DIBMA‐Na) has a similar salting‐out concentration as SMA‐Na. The radius of gyration measurements by static light scattering suggest that at least some fraction of the DIBMA‐Na chains form large intermolecular aggregates. The copolymers of maleic acid–sodium salt with n‐alkenes (n‐CmMA‐Na) in 0.1 N NaAc form small intermolecular aggregates (three to five chains/aggregate). In contrast to these static light scattering results, PGSE NMR diffusion measurements for the above aggregated systems indicate only one diffusion coefficient consistent with the motion of single isolated chains. A plausible explanation for this discrepancy is that the population of the aggregates is too small to be sufficiently detected in the PGSE NMR experiment. Furthermore, it is likely that the aggregate has a larger relaxation rate than the nonaggregate, and therefore has a comparatively reduced signal in the PGSE NMR experiment. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3584–3597, 2004

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