Alphabetical Index
Additional Indexes
Version 5.0.0 (14588 Terms)
DOI: 10.1351/goldbookhttps://doi.org/10.1351/goldbook.C00958
Achain reaction in which the growth of a polymerchain proceeds exclusively by reaction(s) betweenmonomer(s) and reactive site(s) on the polymer chain with regeneration of the reactive site(s) at the end of each growth step.
Notes:
- A chainpolymerization consists ofinitiation andpropagation reactions, and may also includetermination andchain transfer reactions.
- The adjective 'chain' in 'chainpolymerization' denotes a 'chain reaction' rather than a 'polymer chain'.
- Propagation in chainpolymerization usually occurs without the formation of small molecules. However, cases exist where a low-molar-mass by-product is formed, as in thepolymerization of oxazolidine-2,5-diones derived from amino acids (commonly termed amino-acidN-carboxyanhydrides). When a low-molar-mass by-product is formed, the adjective 'condensative' is recommended to give the term 'condensative chain polymerization'.
- The growth steps are expressed by: \[\rm{P}_{x} + \rm{M}\rightarrow \rm{P}_{x + 1}\hspace{5pt}(+\ \rm{L}) \hspace{35pt} \{x\}\in \{1,2,\ \dots \infty\};\] where \(P_{x}\) denotes the growing chain ofdegree of polymerization \(x\), \(M\) amonomer and \(L\) a low-molar-mass by-product formed in the case of condensative chain polymerization.
- The term 'chainpolymerization' may be qualified further, if necessary, to specify the type of chemical reactions involved in the growth step, e.g. ring-opening chainpolymerization, cationic chainpolymerization.
- There exist, exceptionally, some polymerizations that proceedvia chain reactions that, according to the definition, are not chain polymerizations. For example, thepolymerization:proceedsvia a radicalchain reaction withintermolecular transfer of the radical centre. The growth step, however, involves reactions between molecules of all degrees ofpolymerization and, hence, thepolymerization is classified as apolyaddition. If required, the classification can be made more precise and thepolymerization described as a chain-reactionpolyaddition.
