Polyacrylamide
IUPAC name	poly(2-prop-enamide)
Identifiers
CAS number	9003-05-8
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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 best laboratory practice (such as wearing appropriate gloves, lab coat etc. and having safe systems of work) 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 aesthetic facial surgery (see Aquamid).

Contents 1 Uses of polyacrylamide 2 Stability 3 Environmental effects 4 See also 5 External links 6 References

[edit] Uses of polyacrylamide

One of the largest uses for polyacrylamide is to 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, such as a acrylic acid or a salt thereof. The main consequence of this is to give the 'modified' polymer a particular ionic character.

Another common use of polyacrylamide and its derivatives is in subsurface applications such as Enhanced Oil Recovery. High viscosity aqueous solutions can be generated with low concentrations of polyacrylamide polymers, and these can be injected to improve the economics of conventional waterflooding.

It has also been advertised as a soil conditioner called Krilium by Monsanto Company 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.^[1]

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.

[edit] Stability

In dilute aqueous solution, such as is commonly used for Enhanced Oil Recovery applications, polyacrylamide polymers are susceptible to chemical, thermal, and mechanical degradation. Chemical degradation occurs when the labile amine moiety hydrolyzes at elevated temperature or pH, resulting in the evolution of ammonia and a remaining carboxyl group. Thus, the degree of anionicity of the molecule increases. Thermal degradation of the vinyl backbone can occur through several possible radical mechanisms, including the autooxidation of small amounts of iron and reactions between oxygen and residual impurities from polymerization at elevated temperature. Mechanical degradation can also be an issue at the high shear rates experienced in the near-wellbore region.

[edit] Environmental effects

Some older research at first indicated that Polyacrylamide had the potential to host a nerve toxin, however recent research shows otherwise.^[2]

[edit] See also

• Chitosan
• Sodium polyacrylate, a similar material
• Rhoca-Gil

[edit] External links

• Chemical of the Week: Polymers - "Science is Fun" site at University of Wisconsin-Madison
• How do polymer crystals work and why do they absorb so much water? - "How Stuff Works" site
• Polyacrylamide Gels

[edit] References