ABSTRACT
At first glance, the polymer known as poly(ethylene glycol) (PEG) appears to be a simple molecule. It has
the following structure that is characterized by hydroxyl groups at either end of the molecule:
HO---(CH2CH2O)nCH2CH2---OH
It is a linear or branched, neutral polyether available in a variety of molecular weights, and soluble in
water and most organic solvents. Despite its apparent simplicity, this molecule is the focus of much
interest in the biotechnical and biomedical communities. Primarily, this is because PEG is unusually
effective in excluding other polymers from its presence when in an aqueous environment. This property
translates into protein rejection, formation of a two-phase system with other polymers, nonimmuno-
genicity, and nonantigenicity. Also, PEG is nontoxic. The lack of toxicity is reflected in the fact that PEG
is one of the few synthetic polymers approved for internal use by the FDA, appearing in food, cosmetics,
personal care products, and pharmaceuticals.
