Water-soluble polymers with styrenesulfonate and maleic acid units in the backbone

The radical copolymerization of maleic acid (MAc) with sodium p-styrenesulfonate (sodium 4-vinylbenzenesulfonate) (NaSS) in aqueous solution yielded copolymers containing both: carboxylic and sulfonic groups attached to the backbone. By changing initiator concentrations and temperatures, the weight-average molecular weights, Mw, were tailored in the range between 83 · 103 and 265 · 103. The corresponding intrinsic viscosities extended from 0,270 to 810 cm3/g, giving rise to the Mark-Houwink equation: [η] = 7,65 · 10−6 · M0,924 solvent aqueous 0,1 M NaCl; (25°C). The highest degree of conversion at the conditions employed amounted to 83%. Based on the sulfur content found analytically, an equal share of both monomeric units was established. The structure of the copolymer poly[(maleic acid)-co-(sodium p-styrenesulfonate)] obtained was elucidated by means of 13C NMR, 1H NMR and IR spectroscopy. After converting the sulfonate groups to their H+ -form through ion exchange, the copolymer was submitted to potentiometric 0,1 M NaOH titration yielding a dE/dV vs. α curve (with E electromotive force, V volume of titrant and α degree of neutralization), which deviates in shape from theoretical expectations. This deviation was attributed to high ionic strength within the polymeric coils.