Dissociation Behavior of Poly(maleic acid):  Potentiometric Titrations, Viscometry, Pulsed Field Gradient NMR, and Model Calculations

Abstract

Potentiometric titrations, pulsed field gradient NMR, and viscometry of poly(maleic acid) have been carried out in different salt solutions of varying ionic strength. The shape of the titration curve depends strongly on the type of cation used, especially beyond α = 0.5. Above 5 times excess salt concentration, the potentiometric titration curves can be fit satisfactorily to an equation derived on the basis of a random Ising model, using three free parameters: the intrinsic dissociation constant K 0 and two excess free energies εr and εm describing the nearest-neighbor interaction across a racemic and mesomeric bond, respectively. The stereochemistry of PMA is modeled using an additional parameter P r, which is the probability of racemic propagation during synthesis. This parameter was determined by 13C NMR. The results compare favorably with those obtained for other poly(carboxylic acid)s. Except for a gradual expansion of the polymer coil upon charging, no conformational changes are observed by PFG-NMR and viscometry. Rather, attractive intermolecular interactions appear to play a role at high degrees of dissociation.

Synthesis, characterisation and properties of α,β-poly(N-2-hydroxyethyl)-dl-aspartamide-graft-maleic anhydride precursors and their stimuli-responsive hydrogels

“…The initial decrease of pK a up to approximately the condition of half neutralisation can be interpreted postulating an extra-interaction due to the presence of intra-repetitive units H-bonding, that takes into account a stiffer polymer conformation at low a values, eventually destroyed by the increase of protonation degree, as already observed for other similar carboxylated polymers [43,45,46]. The comparison between the FTIR spectra of the two precursors in the m(C@O) spectral region, reported in Fig.…”

Synthesis, Characterization and Behavior in Aqueous Solution of Star‐Shaped Poly(acrylic acid)

“…[29] Potentiometric titrations of linear polyacids and polybases have been performed and discussed. [18,[30][31][32] In contrast to low molecular acids, where distinct deprotonation equilibrium constants, due to distinct ionization processes, can be observed, for polyacids only average equilibrium constants depending on ionization degree can be extracted. A polymer's architecture changes its titration behavior, [24,33] as was shown for hyperbranched polyacids [6] and predicted by Klein Wolterink et al [24] for starshaped weak polyacids by self-consistent field calculations.…”

A Nonaqueous Potentiometric Titration Study of the Dissociation of t-Butyl Methacrylate-Methacrylic Acid Copolymers

“…The acid dissociation can be suppressed by strong electrostatic repulsions of the charged methacrylate anion unit (MA -), as reported concerning aqueous polyacid solution systems. [4][5][6] On the other hand, pKa increased with increasing x for the same α (Fig. 2a).…”

“…The dissociation behavior of various water-soluble polymers has been both experimentally and theoretically reported. [1][2][3][4][5][6][7][8] For a resist resolution in photolithography, acid dissociation of the resist polymers is one of the important factors. Although potentiometric titration is useful as a quantitative analysis of acid dissociation, direct measurements of the acidity of resist polymers cannot be performed by aqueous potentiometric titration since the polymers do not dissolve in water.…”