Page 167 - Carrahers_Polymer_Chemistry,_Eighth_Edition

130 Carraher’s Polymer Chemistry

O O

R H 2 N R

R 1
R
H N R
2
O
O

R R

HO N OH

R 1
HO OH
N

R R

FIGURE 4.10 Curing of two-part epoxy resin adhesives.

Poly(ethylene glycols) are generally designated as to some average molecular weight. Thus,
PEG4000 corresponds to n = about 90 (that is 4,000/44 amu/unit).
Poly(ethylene glycols) come with a variety of end groups. Thus, the monofunctional methyl ether
of PEG, methoxypoly(ethylene glycol) has one of the end groups a methoxy rather than the usual
hydroxyl. They also come in a variety of geometries. Star PEGs have 10–100 PEG units radiating
from a central core. Branched PEGs have 3–10 PEG chains radiating from a central core. Comb
PEGs have multiple PEG chains grafted to a polymer backbone.
Poly(ethylene glycols) have a low toxicity and are employed in a number of products. It forms the
basis for a number of laxatives such as MiraLax, GlycoLax, and Movicol. It is used in a number of
sexual lubricants and skin creams. Bowel irrigations often employ PEG with some electrolytes to
be used before surgery, colonoscopy, or in drug overdoses. It is sold under trade names as Colyte,
TriLyte, Fortrans, GoLately, and GlycoLax for this purpose. It is attached to selected protein drugs
to allow a longer-acting medicinal effect. PEG-interferon alpha is used to treat hepatitis C and
PEG–filgrastim is used to treat neutropenia.

It is employed as the soft segment in PU. PEG is used in toothpaste as a dispersant and as a
lubricant in eye drops. It is also being used in certain body armor. Dr. Pepper adds PEG as an anti-
foaming agent. It has been used to help preserve wood replacing water giving the wood increasing
dimensional stability. Certain gene therapy vectors such as viruses can be coated with PEG to
protect them from inactivation by immune systems and to de-target them from organs, where they
could build up causing a toxic effect.
Because of their ready water solubility, PEGs are often used to impart water solubility to a poly-
mer. This approach has been used to make electrically conductive polymers water soluble as well as
a number of drugs water soluble.

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