POLYACRYLIC ACID (PAA)

Polymer TechnologyBy: Kudzai Hamish Ruzvidzo

B Tech (Chemical Process Systems Engineering)M Tech (Polymer Science and Technology)

vakudzaihamish@gmail.com

Introduction• Polyacrylic acid (PAA) is a polymer made from the monomer acrylic acid.• These long chains contain thousands of monomer units, and the polymer

also has some cross-linking between the chains. • Many polymers, such as polyethylene and polystyrene (used in trash bags,

plastic bottles, and Styrofoam®, for example) are hydrophobic, meaning they repel water. • Polyacrylic acid, however, is very hydrophilic - it attracts water. That's

because of the carboxylic acid groups (COOH) in the polymer, which can hydrogen-bond to water molecules.• Thus PAA is a super-absorbent polymer

Monomer• Polyacrylic acid is made from the monomer acrylic acid• Acrylic acid (IUPAC: prop-2-enoic acid) is an organic compound with

the formula CH2=CHCOOH.• It is the simplest unsaturated carboxylic acid, consisting of a vinyl

group connected directly to a carboxylic acid terminus. • This colorless liquid has a characteristic acrid or tart smell.• It is miscible with water, alcohols, ethers, and chloroform.

Synthesis by Free Radical Mechanism

Synthesis by anionic polymerization

Properties• Hygroscopic, brittle and colorless in nature • In a water solution at neutral pH, PAA is an anionic polymer, i.e. many

of the side chains of PAA will lose their protons and acquire a negative charge. • This makes PAAs polyelectrolytes, with the ability to absorb and retain

water and swell to many times their original volume.• Tg at nearly 106oC• At temperatures above 200 to 250oC, it loses water and becomes an

insoluble crosslinked polymer anhydride. • Solubility of dried PAA in water increases with rise in temperatures.• Concentrated solutions of PAA in water is thixotropic in nature.

Applications

• Disposable diapers• Hand sanitizer• Ion exchange resins• Mascara• Aftershave• Toothpaste• Hair-styling products (gels, dyes, sprays)• Moisturizer• Pet shampoo• Metal polish• Thickening, dispersing, suspending and emulsifying agents in cosmetics,

pharmaceuticals and paints • May inactivate the antiseptic chlorhexidine gluconate

Did you know??• Polyacrylic acid is developed by ReProtect. • It is a gel that may help both block the spread of sexually transmitted

diseases and reduce unwanted pregnancies.• The compound, known as BufferGel, is currently in advanced clinical

trials for its ability to prevent pregnancy.• Source: DrugBank

Record Name: polyacrylic acidURL: http://www.drugbank.ca/drugs/DB05384