Copolymer

A copolymer is a type of polymer made from more than one monomer ingredient. Copolymers made of two, three, or four monomers are sometimes called dipolymers, terpolymers, or quaterpolymers.

Types

Different types of copolymer depend on how the monomers react with each other. The Mayo–Lewis equation is a differential equation that predicts how copolymers form based on reactivity of the monomers.

Alternating copolymers

Structure of an alternating copolymer with the formula (AB)_n.

Alternating copolymers have the same amount of monomers in the same order, coming together to make a single bigger repeating unit. These polymers are both copolymers and homopolymers, with the combined unit being called the implicit monomer of the homopolymer.

These kinds of polymers are normally formed when the monomers do not react with themselves to make homopolymers.

Block copolymers

Structure of a block copolymer with the formula [A]_n[B]_m.

Block copolymers have large groups of a single monomer called blocks. Blocks are themselves made up of smaller units, but these units are different between different blocks.

These kinds of polymers are normally found when the monomers are very reactive with themselves, making large homopolymer blocks that only sometimes change to the other monomer.

Statistical copolymers

Structure of a statistical copolymer with formula A_nB_m.

A statistical copolymer is a copolymer where the repeating units are not in any fixed order, but follow some rule of probability. Statistical copolymers are also often called random copolymers, but this formally only means polymers where the probability of finding a unit does not depend on where it is or the units near it. For these truly random copolymers, that probability is equal to the mole fraction of the monomer.

Statistical copolymers are normally made when the reactivity of the monomers to each other is similar to the reactivity of the monomers with themselves.