Editing Addition polymer

{{Short description|Polymer formed from a chemical reaction with no by-products}}

In [[polymer chemistry]], an '''addition polymer''' is a [[polymer]] that forms by simple linking of [[monomer]]s ''without'' the co-generation of other products. Addition [[polymerization]] differs from [[condensation polymer|condensation polymerization]], which ''does'' co-generate a product, usually water.<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 |author1=D. Margerison |author2=G. C. East |author3=J. E. Spice|isbn=978-0-08-011891-8}}</ref>  Addition polymers can be formed by [[Chain-growth polymerization|chain polymerization]], when the polymer is formed by the sequential addition of monomer units to an active site in a [[chain reaction]], or by [[polyaddition]], when the polymer is formed by [[addition reaction]]s between species of all [[degree of polymerization|degrees of polymerization]]. Addition polymers are formed by the addition of some simple monomer units repeatedly. Generally polymers are unsaturated compounds like alkenes, alkalines etc. The addition polymerization mainly takes place in free radical mechanism. The free radical mechanism of addition polymerization completed by three steps i.e. Initiation of free radical, Chain propagation, Termination of chain.

== Polyolefins ==
Many common addition polymers are formed from [[Saturated and unsaturated compounds|unsaturated]] monomers (usually having a C=C double bond).<ref>{{cite web|url=http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Addition-Polymers-930.html |archive-url=https://archive.today/20121212083558/http://chemed.chem.wisc.edu/chempaths/GenChem-Textbook/Addition-Polymers-930.html |url-status=dead |archive-date=December 12, 2012 |title=Addition Polymers |accessdate=July 17, 2012 }}</ref> The most prevalent addition polymers are polyolefins, i.e. polymers derived by the conversion of olefins (alkenes) to long-chain alkanes.  The [[stoichiometry]] is simple:
:n RCH=CH<sub>2</sub>  →   [RCH-CH<sub>2</sub>]<sub>n</sub>
This conversion can be induced by a variety of [[catalyst]]s including [[free-radical polymerization|free radicals]], [[cationic polymerization|acids]], [[anionic polymerization|carbanions]] and [[coordination polymerization|metal complexes]].

Examples of such polyolefins are [[polyethene]]s, [[polypropylene]], [[PVC]], [[Teflon]], [[Buna rubber]]s, [[polyacrylate]]s, [[polystyrene]], and [[PCTFE]]. 

===Copolymers===
When two or more types of monomers undergo addition polymerization, the resulting polymer is an addition copolymer. [[Saran wrap]], formed from polymerization of [[vinyl chloride]] and [[vinylidene chloride]], is an addition copolymer.<ref name="Stoker2012">{{cite book|author=H. Stephen Stoker|title=Organic and Biological Chemistry|url=https://books.google.com/books?id=z6o_PO4BhRQC&pg=PA65|accessdate=17 July 2012|date=1 January 2012|publisher=Cengage Learning|isbn=978-1-133-10395-0|page=65}}</ref>

==Ring-opening polymerization==
[[Ring-opening polymerization]] is an additive process but tends to give condensation-like polymers but follows the stoichiometry of addition polymerization.  For example, [[polyethylene glycol]] is formed by opening [[ethylene oxide]] rings:
:HOCH<sub>2</sub>CH<sub>2</sub>OH  +  n C<sub>2</sub>H<sub>4</sub>O   →   HO(CH<sub>2</sub>CH<sub>2</sub>O)<sub><sub>n+1</sub></sub>H

[[Nylon 6]] (developed to thwart the [[patent]] on [[Nylon|nylon 6,6]]) is produced by addition polymerization, but chemically resembles typical polyamides.

==Further contrasts with condensation polymers==
One universal distinction between polymerization types is development of molecular weight by the different modes of propagation.  Addition polymers form high molecular weight chains rapidly, with much monomer remaining.  Since addition polymerization has rapidly growing chains and free monomer as its reactants, and condensation polymerization occurs in step-wise fashion between monomers, dimers, and other smaller growing chains, the effect of a polymer molecule's current size on a continuing reaction is profoundly different in these two cases.  This has important effects on the distribution of molecular weights, or [[polydispersity]], in the finished polymer.

== Biodegradation ==
Addition polymers are generally [[chemically inert]], involving strong C-C bonds. For this reason they are non-biodegradable and difficult to recycle. In contrast, condensation polymers tend to be more readily [[biodegradation|bio-degradable]] because their backbones contain weaker bonds.

== History ==
The first useful addition polymer was made by accident in 1933 by [[Imperial Chemical Industries|ICI]] chemists [[Reginald Gibson (chemist)|Reginald Gibson]] and [[Eric Fawcett (chemist)|Eric Fawcett]]. They were carrying out a series of experiments that involved reacting organic compounds under high temperatures and high pressures. They set up an experiment to react ethene with [[benzaldehyde]] in the hope of producing a [[ketone]]. They left the reaction vessel overnight, and the next morning they found a small amount of a white waxy solid. It was shown later that this solid was [[polyethylene]]. 

{{Quote box
 |width = 50%
 |title = [[International Union of Pure and Applied Chemistry|IUPAC]] definition
 |quote = '''Chain polymerization''': [[Chain reaction]] in which the growth of a [[polymer]] chain proceeds exclusively by reaction(s) between monomer(s) and active site(s) on the polymer chain with regeneration of the active site(s) at the end of each growth step.<ref>{{cite journal|title= Glossary of terms related to kinetics, thermodynamics, and mechanisms of polymerization (IUPAC Recommendations 2008)|journal=[[Pure and Applied Chemistry]]|year=2008|volume=80|issue=10|pages=2163–2193|doi=10.1351/pac200880102163|url=http://www.iupac.org/publications/pac/pdf/2008/pdf/8010x2163.pdf |last1=Penczek|first1=Stanisław|last2=Moad|first2=Graeme}}</ref> 
}}
The term "addition polymerization" is deprecated by [[IUPAC]] (International Union of Pure and Applied Chemistry) which recommends the alternative term [[chain-growth polymerisation|chain polymerization]].
{{clear}}

== References ==
{{Reflist}}
*{{cite book|author=Paul J. Flory|title=Principles of Polymer Chemistry|url=https://books.google.com/books?id=CQ0EbEkT5R0C&pg=PA51|accessdate=17 July 2012|year=1953|publisher=Cornell University Press|isbn=978-0-8014-0134-3|page=51}}

[[Category:Polymer chemistry]]
[[Category:Polymerization reactions]]