Chemistry Reference
In-Depth Information
STEP GROWTH POLYMERIZATION
Monomer + Monomer
Dimer
Dimer + Monomer
Trimer
Dimer + Dimer
Tetramer
Trimer + Monomer
Tetramer
Trimer + Dimer
Pentamer
M
M
30-mer + 21-mer
51-mer
Condensation polymerization is the most common kind of step growth poly-
merization. In condensation polymerization, the monomers link together with
loss of a small molecule such as water.
Step growth polymerization is relatively slow. The reaction can be stopped
at any time and low-molecular-weight products (called oligomers) can be
isolated. The monomer disappears early in the reaction because of the for-
mation of the low-molecular-weight products (tetramers, pentamers, and
oligomers). These low-molecular-weight products continue to react with
each other over long reaction times to build up to a fully grown polymer. A
range of molecular weights is obtained. The average of this molecular weight
range is usually taken as the polymer's molecular weight.
