Chemistry Reference
In-Depth Information
COPOLYMERS
• Polymers made with two or more monomers are copolymers.
• Most step growth polymers are copolymers.
• Chain growth copolymers are made to achieve specific properties.
• Chain growth copolymers may be:
Alternating
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A
—
B
—
A
—
B
—
A
—
B
—
A
—
B
—
Random
—
A
—
A
—
B
—
A
—
B
—
B
—
B
—
A
—
A
—
B
—
Block
—A—A—B—B—B—B—A—A—A—B—B—
Graft
—A—A—A—A—A—A—A—A—
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|
B
B
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|
B
B
|
|
Mixtures of two or more monomers can polymerize to form copolymers.
Many copolymers have been developed to combine the best features of each
monomer. For example, poly(vinyl chloride) (called a
homopolymer
because
it is made from a single monomers) is brittle. By copolymerizing vinyl
chloride with vinyl acetate, a copolymer is obtained that is flexible. Arrange-
ment of the monomer units in a copolymer depends on the rates at which
the monomers react with each other. Graft copolymers are formed when a
monomer is initiated by free radical sites created on an already-formed
polymer chain.
