Polyylene glycol (PEG) is a polymer made of
ethylene glycol molecules connected by a chemical reaction. It has a linear
structure, in which the ethylene glycol unit (C2H4O) is
repeatedly linked together to form a long chain. The properties of polyethylene
glycol can be adjusted by controlling the molecular weight (the degree of
polymerization, also known as the length of the polymer), to obtain different
chemical and physical properties.