View source for Condensation polymer

{{Short description|Polymer produced via a condensation reaction}}
{{TopicTOC-Polymer}}
[[File:PET.svg|thumb|[[Polyethylene terephthalate]] (PET) is a common condensation polymer.]]
In [[polymer chemistry]], '''condensation polymers''' are any kind of [[polymer]]s  whose process of [[polymerization]] involves a [[condensation reaction]] (i.e. a small molecule, such as [[water]] or [[methanol]], is produced as a byproduct).  Natural [[protein]]s as well as some common plastics such as [[nylon]] and [[PETE]] are formed in this way. Condensation polymers are formed by polycondensation, when the polymer is formed by condensation reactions between species of all [[Degree of polymerization|degrees of polymerization]], or by condensative [[Chain-growth polymerization|chain polymerization]], when the polymer is formed by sequential addition of monomers to an [[active site]] in a [[chain reaction]].  The main alternative forms of polymerization are chain polymerization and [[polyaddition]], both of which give [[addition polymer]]s.
{{Quote box
| title = [[International Union of Pure and Applied Chemistry|IUPAC]] definition
| quote = '''Polycondensation''':
a polymerization in which the growth of polymer chains proceeds by condensation reactions between molecules of all degrees of polymerization.
Notes:
#The growth steps are expressed by:
#:{{chem2|P_{''x''} + P_{''y''} -> P_{''x''+''y''} + L}} ({{nowrap|1=''x'', ''y'' = 1, 2, …}})
#:where {{chem2|P_{''x''}|}} and {{chem2|P_{''y''}|}} denote chains of degrees of polymerization ''x'' and ''y'', respectively, and L a low-molar-mass by-product.
#The earlier term 'polycondensation' was synonymous with 'condensation polymerization'. The current definitions of polycondensation and condensative chain polymerization were both embraced by the earlier term 'polycondensation'.<ref>{{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)|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}}</ref>
| align = right
| width = 30%
}}
Condensation polymerization is a form of [[step-growth polymerization]].  Linear polymers are produced from [[bifunctional]] monomers, i.e. compounds with two reactive [[end-group]]s. Common condensation polymers include [[polyester]]s, [[polyamide]]s such as [[nylon]], [[polyacetal]]s, and [[protein]]s.<ref>''Introduction to Polymers'' 1987 R.J. Young Chapman & Hall {{ISBN|0-412-22170-5}}</ref><ref>{{cite book|title=An Introduction to Polymer Chemistry|publisher=Pergamon Press|year= 1967 |author=D. Margerison |author2=G. C. East |author3=J. E. Spice|isbn=978-0-08-011891-8}}</ref>
==Polyamides==
One important class of condensation polymers are [[polyamide]]s.<ref>{{cite encyclopedia |author=B. Herzog |author2=M. I. Kohan |author3=S. A. Mestemacher |author4=R. U. Pagilagan |author5=K. Redmond|title=Polyamides|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2013|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a21_179.pub3|isbn=978-3-527-30673-2 |s2cid=241272519 }}</ref> They arise from the reaction of [[carboxylic acid]] and an amine.  Examples include [[nylon]]s and [[protein]]s. When prepared from amino-carboxylic acids, e.g. amino acids, the stoichiometry of the polymerization includes co-formation of water:
:n H<sub>2</sub>N-X-CO<sub>2</sub>H  →  [HN-X-C(O)]<sub>n</sub>  +  (n-1) H<sub>2</sub>O
When prepared from [[diamine]]s and [[dicarboxylic acid]]s, e.g. the production of [[nylon 66]], the polymerization produces two molecules of water per repeat unit:
:n H<sub>2</sub>N-X-NH<sub>2</sub> + n HO<sub>2</sub>C-Y-CO<sub>2</sub>H  →  [HN-X-NHC(O)-Y-C(O)]<sub>n</sub>  +  (2n-1) H<sub>2</sub>O
:[[Image:Condensation polymerization diacid diamine.svg|thumb|left|400px|General chemical structure of one type of condensation polymer]]{{clear}}
==Polyesters==
Another important class of condensation polymers are [[Polyester|polyesters]].<ref>{{cite encyclopedia |author=Horst Köpnick |author2=Manfred Schmidt |author3=Wilhelm Brügging |author4=Jörn Rüter |author5=Walter Kaminsky|title=Polyesters|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2002|publisher=Wiley-VCH|place=Weinheim|doi=10.1002/14356007.a21_227|isbn=3-527-30673-0 }}</ref>  They arise from the reaction of a [[carboxylic acid]] and an alcohol. An example is [[polyethyleneterephthalate]], the common plastic PETE (recycling #1 in the USA):
:n HO-X-OH + n HO<sub>2</sub>C-Y-CO<sub>2</sub>H  →  [O-X-O<sub>2</sub>C-Y-C(O)]<sub>n</sub>  +  (2n-1) H<sub>2</sub>O
[[Image:Poly-(R)-3-hydroxybutyrat.svg|thumb|right|200px|Structure of [[Polyhydroxybutyrate|poly-(''R'')-3-hydroxybutyrate (P3HB)]], a naturally-occurring polymer.]]
==Safety and environmental considerations==
Condensation polymers tend to be more biodegradable than [[addition polymer]]s. The peptide or ester bonds between monomers can be hydrolysed, especially in the presence of catalysts or bacterial [[enzyme]]s.<ref>{{cite journal |last1=Wei |first1=Ren |last2=Zimmermann |first2=Wolfgang |title=Microbial enzymes for the recycling of recalcitrant petroleum-based plastics: how far are we? |journal=Microbial Biotechnology |date=November 2017 |volume=10 |issue=6 |pages=1308–1322 |doi=10.1111/1751-7915.12710|pmid=28371373 |pmc=5658625 |doi-access=free }}</ref>
==See also==
*[[Biopolymer]]
*[[Epoxy resins]]
*[[Polyamide]]
*[[Polyester]]
==References==
{{Reflist}}
==External links==
{{Commons category|Condensation polymerization}}
*[https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/polymers.htm Polymers (and condensation polymers) - Virtual Text of Organic Chemistry, William Reusch]
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{{DEFAULTSORT:Condensation Polymer}}
[[Category:Polymer chemistry]]
[[Category:Polymerization reactions]]