Sodium polymethacrylate
[CAS# 54193-36-1]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic sodium
• Name: Sodium polymethacrylate
• Synonyms: Poly(methacrylic acid sodium salt)
• Molecular Formula: (C₄H₅NaO₂)_n
• Molecular Weight: ~5,400
• CAS Registry Number: 54193-36-1
• EC Number: 611-109-3
• SMILES: CC(=C)C(=O)O[Na]

Properties

• Density: 1.18 g/mL (25 °C) (Expl.)

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P271-P280-P302+P352-P305+P351+P338

Discovery and Applications

Sodium polymethacrylate is a water-soluble polymer derived from the polymerization of methacrylic acid or its salts, specifically in this case the sodium salt form. It consists of repeating units of methacrylate monomers, where the carboxyl groups are neutralized with sodium ions. This polymer is recognized for its ability to absorb and retain large amounts of water, making it an important superabsorbent material.

The development of sodium polymethacrylate began in the mid-20th century alongside research on superabsorbent polymers (SAPs). These polymers were created to address needs in personal hygiene products, agriculture, and industrial applications by leveraging their high water retention capacities. The sodium salt form is particularly valued for its enhanced solubility and swelling behavior in aqueous environments.

Sodium polymethacrylate finds widespread application in products such as diapers, adult incontinence products, and feminine hygiene items. Its superabsorbent properties allow it to absorb water many times its own weight, effectively locking moisture away and improving product comfort and dryness. This ability stems from the polymer’s network structure and the ionic repulsion between the charged carboxylate groups, which causes it to swell extensively when hydrated.

In agriculture, sodium polymethacrylate is used as a soil conditioner to improve water retention in sandy or arid soils. By retaining moisture, it supports better plant growth and reduces the frequency of irrigation needed. It also finds use in seed coatings and controlled-release fertilizer formulations, helping to optimize nutrient delivery and water availability.

Industrial applications include its use as a thickener, binder, or dispersant in cosmetics, detergents, and pharmaceuticals. The polymer’s water-absorbing properties contribute to texture and stability in these formulations. Additionally, sodium polymethacrylate can be used in wastewater treatment processes to aid in flocculation and removal of suspended solids.

The polymer is synthesized by free radical polymerization of methacrylic acid or methacrylate monomers in the presence of neutralizing agents such as sodium hydroxide. The degree of polymerization and neutralization affects its physical properties, including viscosity, swelling capacity, and mechanical strength.

Safety evaluations of sodium polymethacrylate have shown it to be non-toxic and non-irritant under typical use conditions, which supports its widespread use in consumer products. However, dust from the dry polymer can be an irritant to the respiratory tract, so proper handling precautions are recommended during manufacturing.

In summary, sodium polymethacrylate is a versatile superabsorbent polymer widely used in hygiene products, agriculture, and industrial formulations due to its excellent water-absorbing properties. Its synthesis and functional performance have been well established, supporting its role in improving product functionality and environmental water management.

References

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