copolymer (rus. сополимер) — a polymer whose macromolecules consist of several types of monomers.

Description

Copolymers can be synthesised, for example, during polymerisation reactions which flow in a mixture of monomers of two or more types. The distribution of monomer units of different types can be described by different laws. If units of various types are located in strict order and alternate along the chain then such a copolymer is called regular, built by the ABABABAB pattern (A and B – different monomer units). More complex regular sequences of alternating units are also possible; they are typical, in particular, for the arrangement of amino acid residues in some proteins. In other cases, copolymers are called statistical (irregular).

Stereoregular copolymers may include not only copolymers but also homopolymers which consist of orderly arranged monomer units with different stereoconfiguration. In a gradient copolymer the average composition of respective chain regions gradually changes from one end of the macromolecule to the other. Copolymers in which units of each type form long enough continuous sequences alternating within the macromolecule are called block copolymers. The latter are called regular if their units' length and alternation pattern follow a certain periodicity. When units' length becomes shorter the difference between block copolymers and statistical copolymers gradually disappears. In grafted block copolymers main chains composed of units of one type are attached with side chains built of units of another type which forms a comb-shaped macromolecule.

Biopolymers such as proteins and nucleic acidsDNA and RNA are copolymers built of 20 types of amino acids (for proteins) and four types of nucleotides (for nucleic acids). Sequences of DNA nucleotide base pairs in the 23 human chromosomes are responsible for the transmission of hereditary information, thus forming the human genome.

Authors

  • Govorun Elena N.
  • Nazarov Victor G.

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