Polyacrylamide

Polyacrylamide (IUPAC poly(2-propenamide) or poly(1-carbamoylethylene)) is a polymer (-CH₂CHCONH₂-) formed from acrylamide subunits that can also be readily cross-linked. Acrylamide needs to be handled using good laboratory practices (GLP) to avoid poisonous exposure since it is a neurotoxin. Polyacrylamide is not toxic, but unpolymerized acrylamide can be present in the polymerized acrylamide. Therefore it is recommended to handle it with caution. In the cross-linked form, it is highly water-absorbent, forming a soft gel used in such applications as polyacrylamide gel electrophoresis and in manufacturing soft contact lenses. In the straight-chain form, it is also used as a thickener and suspending agent. More recently, it has been used as a subdermal filler for æsthetic facial surgery (see Aquamid).

Uses of polyacrylamide

One of the largest uses for polyacrylamide is flocculate or coagulate solids in a liquid. This process applies to wastewater treatment, and processes like paper making. Most polyacrylamide is supplied in a liquid form. The liquid is subcategorized as solution and emulsion polymer.Even though these products are often called 'polyacrylamide', many are actually copolymers of acrylamide and one or more other chemical species. The main consequence of this is to give the 'modified' polymer some ionic character.

It has also been advertised as a soil conditioner called Krilium by Monsanto in the 1950s and today "MP", which is stated to be a "unique formulation of PAM (water-soluble polyacrylamide)". The anionic form of polyacrylamide is frequently used as a soil conditioner on farm land and construction sites for erosion control, in order to protect the water quality of nearby rivers and streams. [Wisconsin Department of Transportation. Madison, WI. [http://www.dot.wisconsin.gov/library/research/docs/finalreports/tau-finalreports/polyacryl.pdf "Polyacrylamide as a Soil Stabilizer for Erosion Control."] January 2001. Report No. WI 06-98.]

The polymer is also used to make Gro-Beast toys, which expand when placed in water, as the Test Tube Aliens.

The ionic form of polyacrylamide has found an important role in the potable water treatment industry. Trivalent metal salts like ferric chloride and aluminium chloride are bridged by the long polymer chains of polyacrylamide. This results in significant enhancement of the flocculation rate. This allows water treatment plants to greatly improve the removal of total organic content (TOC) from raw water.

Environmental effects

Some research [Smith, E. A., S. L. Prues, F. W. Oehme. [http://www.mindfully.org/Plastic/Polymers/Polyacrylamides-Degradation1jun97.htm "Environmental Degradation of Polyacrylamides and its Effects of Environmental (Outdoor) Exposure."] "Ecotoxicology and Environmental Safety 37(1)." June 1, 1997.] indicates that polyacrylamide can degrade under normal environmental conditions, releasing acrylamide, a known nerve toxin.

Some older research at first indicated that Polyacrylamide had the potential to host a nerve toxin, however recent research shows otherwise. [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VB5-3YXB1NM-D&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0bc485f58dfc0c83d608bdd91bd019ca]

ee also

* Chitosan
* Sodium polyacrylate, a similar material

External links

* [http://scifun.chem.wisc.edu/CHEMWEEK/polymers/polymers.html Chemical of the Week: Polymers] - "Science is Fun" site at University of Wisconsin-Madison
* [http://science.howstuffworks.com/question581.htm How do polymer crystals work and why do they absorb so much water?] - "How Stuff Works" site
* [http://www.gel-electrophoresis.com/gels/articles/polyacrylamide-gels/ Polyacrylamide Gels]

References