Sodium polyaspartate

Sodium polyaspartate

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Names
IUPAC name polyaspartic acid sodium salt
Identifiers
CAS Number	94525-01-6 (for (α,β)-DL-polysodiumaspartate)
Properties
Chemical formula	(C4H4NNaO3)n
Molar mass	variable
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Sodium polyaspartate is a sodium salt of polyaspartic acid. It is biodegradable condensation polymer based on the amino acid aspartic acid.

Polymerization

The polymerization reaction is an example of a step-growth polymerization to a polyamide and in one practical procedure aspartic acid is simply heated to 180 °C resulting in water release and the formation of a poly(succinimide). In the subsequent step, this polymer is reacted with sodium hydroxide in water, which hydrolyzes one of the two amide bonds of the succinimide ring to form a sodium carboxylate. The remaining amide bond is thus the linkage between successive aspartate units. Each aspartate unit is identified as α or β according to which carbonyl of it is part of the polymer chain. The α form has one carbon in the backbone in addition to the carbonyl itself (and a two-carbon sidechain) whereas the β form has two carbons in the backbone in addition to the carbonyl itself (and a one-carbon sidechain). This reaction gives a sodium poly(aspartate) copolymer composed of approximately 30% α-linkages and 70% β-linkages.

Synthesis of sodium poly(aspartate)

Uses

This material can be synthesized in an environmentally friendly way and is biodegradeable, thus it is a green alternative to several materials such as sodium polyacrylate used in disposable diapers and agriculture.

In addition and due to its water-solubility and ability to chelate metal ions, polyaspartate is used as a biodegradeable anti-scaling agent and a corrosion inhibitor.

See also

Polyaspartic acid