polyaddition
{{Short description|Polymer formation through individual independent addition reactions}}
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A polymerization in which the growth of polymer chains proceeds by addition reactions between molecules of all degrees of polymerization.
Notes:
1. The growth steps are expressed by:
Px+Py → Px+y {x}∈{1,2,…∞};{y}∈{1,2,…∞}
where Px and Py denote chains of degrees of polymerization x and y, respectively.
2. The earlier term 'addition polymerization' embraced both the current concepts of 'polyaddition' and 'chain polymerization', but did not include 'condensative chain polymerization'.{{Cite journal|last1=Jenkins|first1=A. D.|last2=Kratochvíl|first2=P.|last3=Stepto|first3=R. F. T.|last4=Suter|first4=U. W.|date=1996-01-01|title=Glossary of basic terms in polymer science (IUPAC Recommendations 1996. See definition 3.8)|url=https://www.degruyter.com/view/journals/pac/68/12/article-p2287.xml|journal=Pure and Applied Chemistry|language=en|volume=68|issue=12|pages=2287–2311|doi=10.1351/pac199668122287|s2cid=98774337|issn=0033-4545|doi-access=free}}
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Polyaddition (or addition polymerisation {{Cite web |title=addition polymerization {{!}} chemical reaction {{!}} Britannica |url=https://www.britannica.com/science/addition-polymerization |access-date=2022-05-10 |website=www.britannica.com |language=en}}{{Cite web |date=2019-05-26 |title=10.3: Addition Polymerization - One + One + One + ... Gives One! |url=https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Chemistry_for_Changing_Times_(Hill_and_McCreary)/10%3A_Polymers/10.03%3A_Addition_Polymerization_-_One__One__One__..._Gives_One |access-date=2022-05-10 |website=Chemistry LibreTexts |language=en}}) is a polymerization reaction that forms polymers via individual independent addition reactions. Polyaddition occurs as a reaction between functional groups on molecules with low degrees of polymerization, such as dimers, trimers and oligomers, to form species of higher molar mass. Only at nearly complete conversions does the polymer form, as in polycondensation and in contrast to chain polymerization.{{cite journal|title=Glossary of basic terms in polymer science (IUPAC Recommendations 1996. See definition 3.6)|journal=Pure and Applied Chemistry|year=1996|volume=68|issue=12|pages=2287–2311 |doi=10.1351/pac199668122287|url=http://pac.iupac.org/publications/pac/pdf/1996/pdf/6812x2287.pdf|last1=Jenkins|first1=A. D.|last2=Kratochvíl|first2=P.|last3=Stepto|first3=R. F. T.|last4=Suter|first4=U. W.|s2cid=98774337}}
A typical polyaddition is the formation of a polyurethane.
:Image:Polyaddition Polyurethane V.2.1.png{{clear left}}
