https://doi.org/10.1351/goldbook.C00958
A
chain reaction
in which the growth of a polymer
chain
proceeds exclusively by reaction(s) between
monomer(s)
and reactive site(s) on the polymer chain with regeneration of the reactive site(s) at the end of each growth step.
Notes:
  1. A chain
    polymerization
    consists of
    initiation
    and
    propagation
    reactions, and may also include
    termination
    and
    chain transfer
    reactions.
  2. The adjective 'chain' in 'chain
    polymerization
    ' denotes a '
    chain reaction
    ' rather than a 'polymer chain'.
  3. Propagation
    in chain
    polymerization
    usually occurs without the formation of small molecules. However, cases exist where a low-molar-mass by-product is formed, as in the
    polymerization
    of oxazolidine-2,5-diones derived from amino acids (commonly termed amino-acid N-carboxy
    anhydrides
    ). When a low-molar-mass by-product is formed, the adjective 'condensative' is recommended to give the term condensative chain polymerization
  4. The growth steps are expressed by: Px+MPx+1(+ L){x}{1,2, }; where Px denotes the growing chain of
    degree of polymerization
    x, M a
    monomer(s)
    and L a low-molar-mass by-product formed in the case of condensative chain polymerization.
  5. The term 'chain
    polymerization
    ' may be qualified further, if necessary, to specify the type of chemical reactions involved in the growth step, e.g. ring-opening chain
    polymerization
    , cationic chain
    polymerization
    .
  6. There exist, exceptionally, some polymerizations that proceed via chain reactions that, according to the definition, are not chain polymerizations. For example, the
    polymerization
    :
    proceeds via a radical
    chain reaction
    with
    intermolecular
    transfer of the radical centre. The growth step, however, involves reactions between molecules of all degrees of
    polymerization
    and, hence, the
    polymerization
    is classified as a
    polyaddition
    . If required, the classification can be made more precise and the
    polymerization
    described as a chain-reaction
    polyaddition
    .
Source:
PAC, 1996, 68, 2287. (Glossary of basic terms in polymer science (IUPAC Recommendations 1996)) on page 2306 [Terms] [Paper]