Physical Properties of Sodium p-Styrene Sulfonate-Maleic Acid Copolymer (SSS/MA)

Sodium p-styrene sulfonate-maleic acid copolymer (commonly abbreviated as PSSMA or SSS/MA) is a synthetic polyelectrolyte that combines a h3ly ionized sulfonate group with a weakly ionized carboxylic acid group. Its physical properties are primarily dictated by its molecular weight, the molar ratio of the two monomers (styrene sulfonate to maleic acid), and its ionic nature.

Key Physical Properties

Property Typical Value / Description Notes

Appearance Faint beige to beige powder Also supplied as aqueous solutions

Molecular Weight Average Mw ~20,000 Molecular weight can vary; some grades are ~3,000

Solubility Soluble in water Forms a clear, transparent solution

Viscosity 30 cP (25 wt. % in H₂O) Viscosity varies with concentration; 30% solutions can be ≤200 cP

Density 0.94 g/mL (at 25 °C) For solid product; some sources report ~0.801 g/mL

pH (1% aq. solution) 6.00 – 8.50 Near neutral

Thermal Stability Stable up to 250 °C Determined by thermogravimetric analysis

Structure-Property Relationships

The physical behavior of PSSMA is closely linked to its chemical composition:

Strong vs. Weak Electrolyte: The styrene sulfonate unit acts as a h3, pH-independent electrolyte, providing a high charge density and excellent dispersing ability. The maleic acid unit is a weak electrolyte, making the overall polymer's solubility and chain conformation responsive to pH changes .

Charge Density: The presence of both sulfonate and carboxylate groups results in a very high anionic charge density. This is a key factor behind its effectiveness as a dispersant for pigments, clays, and fillers .

Copolymer Ratio: The ratio of SSS to MA units is a critical variable. For example, the 3:1 ratio provides a higher density of h3 sulfonate groups, whereas the 1:1 ratio offers a balance between h3 and weak ionic groups, allowing for more tailored properties .