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In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks.^[1]^[2]^[3] There are many forms of polymerization^[4] and different systems exist to categorize them.

In chemical compounds, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the functional groups present in the reactants^[3] and their inherent steric effects. In more straightforward polymerizations, alkenes form polymers through relatively simple radical reactions; in contrast, reactions involving substitution at a carbonyl group require more complex synthesis due to the way in which reactants polymerize.^[3]

As alkenes can polymerize in somewhat straightforward radical reactions, they form useful compounds such as polyethylene and polyvinyl chloride (PVC),^[3] which are produced in high tonnages each year^[3] due to their usefulness in manufacturing processes of commercial products, such as piping, insulation and packaging. In general, polymers such as PVC are referred to as "homopolymers", as they consist of repeated long chains or structures of the same monomer unit, whereas polymers that consist of more than one monomer unit are referred to as copolymers (or co-polymers).^[5]

Other monomer units, such as formaldehyde hydrates or simple aldehydes, are able to polymerize themselves at quite low temperatures (ca. −80 °C) to form trimers;^[3] molecules consisting of 3 monomer units, which can cyclize to form ring cyclic structures, or undergo further reactions to form tetramers,^[3] or 4 monomer-unit compounds. Such small polymers are referred to as oligomers.^[3] Generally, because formaldehyde is an exceptionally reactive electrophile it allows nucleophilic addition of hemiacetal intermediates, which are in general short-lived and relatively unstable "mid-stage" compounds that react with other non-polar molecules present to form more stable polymeric compounds.

Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous. This phenomenon is known as autoacceleration, and can cause fires and explosions.

Step-growth vs. chain-growth polymerization

Step-growth and chain-growth are the main classes of polymerization reaction mechanisms. The former is often easier to implement but requires precise control of stoichiometry. The latter more reliably affords high molecular-weight polymers, but only applies to certain monomers.

Step-growth

In step-growth (or step) polymerization, pairs of reactants, of any lengths, combine at each step to form a longer polymer molecule. The average molar mass increases slowly. Long chains form only late in the reaction.^[6]^[7]

Step-growth polymers are formed by independent reaction steps between functional groups of monomer units, usually containing heteroatoms such as nitrogen or oxygen. Most step-growth polymers are also classified as condensation polymers, since a small molecule such as water is lost when the polymer chain is lengthened. For example, polyester chains grow by reaction of alcohol and carboxylic acid groups to form ester links with loss of water. However, there are exceptions; for example polyurethanes are step-growth polymers formed from isocyanate and alcohol bifunctional monomers) without loss of water or other volatile molecules, and are classified as addition polymers rather than condensation polymers.

Step-growth polymers increase in molecular weight at a very slow rate at lower conversions and reach moderately high molecular weights only at very high conversion (i.e., >95%). Solid state polymerization to afford polyamides (e.g., nylons) is an example of step-growth polymerization.^[8]

Chain-growth

In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical, cation, or anion. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers. Long chains are formed from the beginning of the reaction.^[6]^[7]

Chain-growth polymerization (or addition polymerization) involves the linking together of unsaturated monomers, especially containing carbon-carbon double bonds. The pi-bond is lost by formation of a new sigma bond. Chain-growth polymerization is involved in the manufacture of polymers such as polyethylene, polypropylene, polyvinyl chloride (PVC), and acrylate. In these cases, the alkenes RCH=CH₂ are converted to high molecular weight alkanes (-RCHCH₂-)_n (R = H, CH₃, Cl, CO₂CH₃).

Other forms of chain growth polymerization include cationic addition polymerization and anionic addition polymerization. A special case of chain-growth polymerization leads to living polymerization. Ziegler–Natta polymerization allows considerable control of polymer branching.

Polymerization of ethylene

Diverse methods are employed to manipulate the initiation, propagation, and termination rates during chain polymerization. A related issue is temperature control, also called heat management, during these reactions, which are often highly exothermic. For example, for the polymerization of ethylene, 93.6 kJ of energy are released per mole of monomer.^[8]

The manner in which polymerization is conducted is a highly evolved technology. Methods include emulsion polymerization, solution polymerization, suspension polymerization, and precipitation polymerization. Although the polymer dispersity and molecular weight may be improved, these methods may introduce additional processing requirements to isolate the product from a solvent.

Photopolymerization

Most photopolymerization reactions are chain-growth polymerizations which are initiated by the absorption of visible^[9] or ultraviolet light. Photopolymerization can also be a step-growth polymerization.^[10] The light may be absorbed either directly by the reactant monomer (direct photopolymerization), or else by a photosensitizer which absorbs the light and then transfers energy to the monomer. In general, only the initiation step differs from that of the ordinary thermal polymerization of the same monomer; subsequent propagation, termination, and chain-transfer steps are unchanged.^[6] In step-growth photopolymerization, absorption of light triggers an addition (or condensation) reaction between two comonomers that do not react without light. A propagation cycle is not initiated because each growth step requires the assistance of light.^[11]

Photopolymerization can be used as a photographic or printing process because polymerization only occurs in regions which have been exposed to light. Unreacted monomer can be removed from unexposed regions, leaving a relief polymeric image.^[6] Several forms of 3D printing—including layer-by-layer stereolithography and two-photon absorption 3D photopolymerization—use photopolymerization.^[12]

Multiphoton polymerization using single pulses have also been demonstrated for fabrication of complex structures using a digital micromirror device.^[13]

References

^ "Polymerization". The IUPAC Compendium of Chemical Terminology. 2014. doi:10.1351/goldbook.P04740.
^ Young, Robert J. (1981). Introduction to polymers. London: Chapman and Hall. ISBN 0-412-22170-5. OCLC 8086791.
^ ^a ^b ^c ^d ^e ^f ^g ^h Clayden, Jonathan; Greeves, Nick; Warren, Stuart (2001). Organic chemistry. Oxford: Oxford University Press. pp. 1450–1466. ISBN 0-19-850347-4. OCLC 43338068.
^ Manas, Chanda (2023). Introduction to Polymer Science and Chemistry:A Problem-Solving Approach (2nd ed.). CRC Press (published 2013). ISBN 978-1-4665-5385-9.
^ Cowie, J. M. G. (2008). Polymers : chemistry and physics of modern materials. V. Arrighi (3rd ed.). Boca Raton: CRC Press. p. 4. ISBN 978-0-8493-9813-1. OCLC 82473191.
^ ^a ^b ^c ^d Allcock, H. R.; Lampe, Frederick Walter; Mark, James E. (2003). Contemporary polymer chemistry. Frederick Walter Lampe, James E. Mark (3rd ed.). Upper Saddle River, N.J.: Pearson/Prentice Hall. pp. 29–30. ISBN 0-13-065056-0. OCLC 51096012.
^ ^a ^b Fried, Joel R. (2003). Polymer science and technology (2nd ed.). Upper Saddle River, NJ: Prentice Hall Professional Technical Reference. p. 23. ISBN 0-13-018168-4. OCLC 51769096.
^ ^a ^b Jeremic, Dusan (2014). "Polyethylene". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 1–42. doi:10.1002/14356007.a21_487.pub3. ISBN 9783527306732.
^ McKenzie, Thomas G.; Fu, Qiang; Wong, Edgar H. H.; Dunstan, Dave E.; Qiao, Greg G. (23 June 2015). "Visible Light Mediated Controlled Radical Polymerization in the Absence of Exogenous Radical Sources or Catalysts" (PDF). Macromolecules. 48 (12): 3864–3872. Bibcode:2015MaMol..48.3864M. doi:10.1021/acs.macromol.5b00965. ISSN 0024-9297.
^ Kaya, Kerem (January 2023). "A green and fast method for PEDOT: Photoinduced step-growth polymerization of EDOT". Reactive and Functional Polymers. 182: 105464. doi:10.1016/j.reactfunctpolym.2022.105464.
^ Soto, Marc; Sebastián, Rosa María; Marquet, Jordi (2014). "Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols". J. Org. Chem. 79 (11): 5019–5027. doi:10.1021/jo5005789. PMID 24820955.
^ Wang, Xifan; Schmidt, Franziska; Hanaor, Dorian; Kamm, Paul H.; Li, Shuang; Gurlo, Aleksander (May 2019). "Additive manufacturing of ceramics from preceramic polymers". Additive Manufacturing. 27: 80–90. arXiv:1905.02060. doi:10.1016/j.addma.2019.02.012. S2CID 104470679.
^ Mills, Benjamin; Grant-Jacob, James A; Feinaeugle, Matthias; Eason, Robert W (17 June 2013). "Single-pulse multiphoton polymerization of complex structures using a digital multimirror device" (PDF). Optics Express. 21 (12): 14853–8. Bibcode:2013OExpr..2114853M. doi:10.1364/oe.21.014853. ISSN 1094-4087. PMID 23787672.

[1] "Polymerization". The IUPAC Compendium of Chemical Terminology. 2014. doi:10.1351/goldbook.P04740.

[2] Young, Robert J. (1981). Introduction to polymers. London: Chapman and Hall. ISBN 0-412-22170-5. OCLC 8086791.

[clayden_organic-3] ^ ^a ^b ^c ^d ^e ^f ^g ^h Clayden, Jonathan; Greeves, Nick; Warren, Stuart (2001). Organic chemistry. Oxford: Oxford University Press. pp. 1450–1466. ISBN 0-19-850347-4. OCLC 43338068.

[4] Manas, Chanda (2023). Introduction to Polymer Science and Chemistry:A Problem-Solving Approach (2nd ed.). CRC Press (published 2013). ISBN 978-1-4665-5385-9.

[5] Cowie, J. M. G. (2008). Polymers : chemistry and physics of modern materials. V. Arrighi (3rd ed.). Boca Raton: CRC Press. p. 4. ISBN 978-0-8493-9813-1. OCLC 82473191.

[:0-6] Allcock, H. R.; Lampe, Frederick Walter; Mark, James E. (2003). Contemporary polymer chemistry. Frederick Walter Lampe, James E. Mark (3rd ed.). Upper Saddle River, N.J.: Pearson/Prentice Hall. pp. 29–30. ISBN 0-13-065056-0. OCLC 51096012.

[:1-7] Fried, Joel R. (2003). Polymer science and technology (2nd ed.). Upper Saddle River, NJ: Prentice Hall Professional Technical Reference. p. 23. ISBN 0-13-018168-4. OCLC 51769096.

[ullmannC2-8] Jeremic, Dusan (2014). "Polyethylene". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. pp. 1–42. doi:10.1002/14356007.a21_487.pub3. ISBN 9783527306732.

[9] McKenzie, Thomas G.; Fu, Qiang; Wong, Edgar H. H.; Dunstan, Dave E.; Qiao, Greg G. (23 June 2015). "Visible Light Mediated Controlled Radical Polymerization in the Absence of Exogenous Radical Sources or Catalysts" (PDF). Macromolecules. 48 (12): 3864–3872. Bibcode:2015MaMol..48.3864M. doi:10.1021/acs.macromol.5b00965. ISSN 0024-9297.

[10] Kaya, Kerem (January 2023). "A green and fast method for PEDOT: Photoinduced step-growth polymerization of EDOT". Reactive and Functional Polymers. 182: 105464. doi:10.1016/j.reactfunctpolym.2022.105464.

[Soto_2014-11] Soto, Marc; Sebastián, Rosa María; Marquet, Jordi (2014). "Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols". J. Org. Chem. 79 (11): 5019–5027. doi:10.1021/jo5005789. PMID 24820955.

[12] Wang, Xifan; Schmidt, Franziska; Hanaor, Dorian; Kamm, Paul H.; Li, Shuang; Gurlo, Aleksander (May 2019). "Additive manufacturing of ceramics from preceramic polymers". Additive Manufacturing. 27: 80–90. arXiv:1905.02060. doi:10.1016/j.addma.2019.02.012. S2CID 104470679.

[13] Mills, Benjamin; Grant-Jacob, James A; Feinaeugle, Matthias; Eason, Robert W (17 June 2013). "Single-pulse multiphoton polymerization of complex structures using a digital multimirror device" (PDF). Optics Express. 21 (12): 14853–8. Bibcode:2013OExpr..2114853M. doi:10.1364/oe.21.014853. ISSN 1094-4087. PMID 23787672.

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-{{Short description|chemical reaction to form polymer chains}}
+{{Short description|Chemical reaction to form polymer chains}}
+{{TopicTOC-Polymer}}
 {{Use American English|date=November 2020}}<!-- and IUPAC spelling (aluminium, sulfur, caesium) -->
 {{Use dmy dates|date=November 2020}}
+In [[polymer chemistry]], '''polymerization''' ([[American English]]), or '''polymerisation''' ([[British English]]), is a process of reacting [[monomer|monomer molecule]]s together in a [[chemical reaction]] to form  [[polymer]] chains or three-dimensional networks.<ref>{{cite book |doi=10.1351/goldbook.P04740 |doi-access=free |chapter=Polymerization |title=The IUPAC Compendium of Chemical Terminology |year=2014}}</ref><ref>{{Cite book |last=Young |first=Robert J. |url= |title=Introduction to polymers |publisher=Chapman and Hall |year=1981 |isbn=0-412-22170-5 |location=London |oclc=8086791}}</ref><ref name="clayden_organic">{{Cite book |last1=Clayden |first1=Jonathan |url= |title=Organic chemistry |last2=Greeves |first2=Nick |last3=Warren |first3=Stuart |publisher=Oxford University Press |year=2001 |isbn=0-19-850347-4 |location=Oxford |pages=1450–1466 |oclc=43338068}}</ref> There are many forms of polymerization<ref>{{Cite book |last=Manas |first=Chanda |title=Introduction to Polymer Science and Chemistry:A Problem-Solving Approach |publisher=CRC Press |year=2023 |isbn=978-1-4665-5385-9 |edition=2nd |publication-date=2013}}</ref> and different systems exist to categorize them.
-{{Quote box
- |title =[[International Union of Pure and Applied Chemistry|IUPAC]] definition
- |quote = Polymerization: The process of converting a [[monomer]] or a mixture of monomers into a [[polymer]].<ref>{{cite journal|title=Glossary of basic terms in polymer science (IUPAC Recommendations 1996)|journal=[[Pure and Applied Chemistry]]|year=1996|volume=68|issue=12|pages=2287–2311|doi=10.1351/pac199668122287|url=https://www.iupac.org/publications/pac/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}} See definition 3.1, p. 2305.</ref>
-}}
-[[File:Polystyrene formation.PNG|thumb|right|400px|An example of '''alkene polymerization''', in which each [[styrene]] monomer's double bond reforms as a single bond plus a bond to another styrene monomer. The product is [[polystyrene]].]]
+[[File:IUPAC definition for polymerization.png|thumb|right|550px|link=https://doi.org/10.1351/goldbook.P04740|IUPAC definition for polymerization]]
-In [[polymer chemistry]], '''polymerization''' ([[American English]]), or '''polymerisation''' ([[British English]]), is a process of reacting [[monomer|monomer molecule]]s together in a [[chemical reaction]] to form  [[polymer]] chains or three-dimensional networks.<ref>Young, R. J. (1987) ''Introduction to Polymers'', Chapman & Hall {{ISBN|0-412-22170-5}}</ref><ref>[http://goldbook.iupac.org/P04740.html International Union of Pure and Applied Chemistry, ''et al.'' (2000) ''IUPAC Gold Book'', '''Polymerization''']</ref><ref name="clayden_organic">Clayden, J., Greeves, N. and Warren, S. (2000). [https://books.google.com/books?id=kQgu2j_ber0C&printsec=frontcover ''Organic chemistry''], Oxford University Press {{ISBN|0198503466}} pp. 1450–1466</ref> There are many forms of polymerization and different systems exist to categorize them.
+In [[chemical compound]]s, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the [[functional group]]s present in the reactants<ref name="clayden_organic" /> and their inherent [[steric effects]]. In more straightforward polymerizations, [[alkenes]] form polymers through relatively simple [[free-radical reaction|radical reactions]]; in contrast, reactions involving substitution at a [[carbonyl group]] require more complex synthesis due to the way in which reactants polymerize.<ref name="clayden_organic"/>
+[[File:Polystyrene formation.PNG|thumb|right|400px|An example of '''alkene polymerization''', in which each [[styrene]] monomer's double bond reforms as a single bond plus a bond to another styrene monomer. The product is [[polystyrene]].]]
+As alkenes can polymerize in somewhat straightforward radical reactions, they form useful compounds such as [[polyethylene]] and [[polyvinyl chloride]] (PVC),<ref name="clayden_organic"/> which are produced in high tonnages each year<ref name="clayden_organic"/> due to their usefulness in manufacturing processes of commercial products, such as piping, insulation and packaging. In general, polymers such as PVC are referred to as "'''homopolymers'''", as they consist of repeated long chains or structures of the same monomer unit, whereas polymers that consist of more than one monomer unit are referred to as [[copolymer]]s (or co-polymers).<ref>{{Cite book |last=Cowie |first=J. M. G. |url= |title=Polymers : chemistry and physics of modern materials |publisher=CRC Press |others=V. Arrighi |year=2008 |isbn=978-0-8493-9813-1 |edition=3rd |location=Boca Raton |pages=4 |oclc=82473191}}</ref>
-==Overview==
 {| align="right" class="infobox" style="text-align:center;"
 |
 <div style="font-size:14px; font-weight:bold;">Homopolymers</div>
 :<math>A + A + A+... \rightarrow AAAA ...</math>
 <div style="font-size:14px; font-weight:bold;">Copolymers</div>
 :<math>A + B + A+B... \rightarrow ABAB ...</math>
+:<math>A + B + A+B... \rightarrow AABB ...</math>
+:<math>A + B + A+B... \rightarrow BBAB ...</math>
 |}
-In [[chemical compound]]s, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the [[functional group]]s present in the reactants<ref name="clayden_organic"/> and their inherent [[steric effects]]. In more straightforward polymerizations, [[alkenes]] form polymers through relatively simple [[free-radical reaction|radical reactions]]; in contrast, reactions involving substitution at a [[carbonyl group]] require more complex synthesis due to the way in which reactants polymerize.<ref name="clayden_organic" /> [[Alkane]]s can also be polymerized, but only with the help of strong acids.<ref>Roberts, Durward T., JR. and Lawrence E. Calihan. "[http://www.tandfonline.com/doi/abs/10.1080/00222337308066378?journalCode=lmsa19 Polymerization (Polycondensation) of Alkanes over Fluosulfonic Acid and Antimony Pentafluoride]". Journal of Macromolecular Science, Part A Vol. 7 , Iss. 8, 1973</ref>
+Other monomer units, such as [[formaldehyde]] hydrates or simple aldehydes, are able to polymerize themselves at quite low temperatures (ca. −80&nbsp;°C) to form [[trimer (chemistry)|trimer]]s;<ref name="clayden_organic"/> molecules consisting of 3 monomer units, which can [[cyclization|cyclize]] to form ring cyclic structures, or undergo further reactions to form [[tetramer]]s,<ref name="clayden_organic"/> or 4 monomer-unit compounds. Such small polymers are referred to as [[oligomer]]s.<ref name="clayden_organic"/> Generally, because formaldehyde is an exceptionally reactive electrophile it allows [[nucleophile|nucleophilic]] addition of [[hemiacetal]] intermediates, which are in general short-lived and relatively unstable "mid-stage" compounds that react with other non-polar molecules present to form more stable polymeric compounds.
-As alkenes can polymerize in somewhat straightforward radical reactions, they form useful compounds such as [[polyethylene]] and [[polyvinyl chloride]] (PVC),<ref name="clayden_organic" /> <ref>{{Cite web|last=Chako|first=Sydney|title=Addition Polymers And Macromolecules (O Level Chemistry)|url=https://sytech.co.zw/posts/addition-polymers-and-macromolecules-o-level-chemistry/|access-date=2021-11-21|website=sytech.co.zw|language=en-US}}</ref>which are produced in high tonnages each year<ref name="clayden_organic" /> due to their usefulness in manufacturing processes of commercial products, such as piping, insulation and packaging. In general, polymers such as PVC are referred to as "'''homopolymers'''," as they consist of repeated long chains or structures of the same monomer unit, whereas polymers that consist of more than one monomer unit are referred to as [[copolymer]]s (or co-polymers).<ref>Cowie, J.M.G. (1991) ''Polymers: Chemistry and Physics of Modern Materials'', Chapman and Hall, p. 4 {{ISBN|0849398134}}</ref>
+Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous. This phenomenon is known as [[autoacceleration]], and can cause fires and explosions.
-Other monomer units, such as formaldehyde hydrates or simple aldehydes, are able to polymerize themselves at quite low temperatures (ca. −80&nbsp;°C) to form [[trimer (chemistry)|trimer]]s;<ref name="clayden_organic" /> molecules consisting of 3 monomer units, which can cyclize to form ring cyclic structures, or undergo further reactions to form [[tetramer]]s,<ref name="clayden_organic" /> or 4 monomer-unit compounds. Such small polymers are referred to as [[oligomer]]s.<ref name="clayden_organic" /> Generally, because formaldehyde is an exceptionally reactive electrophile it allows [[nucleophile|nucleophilic]] addition of [[hemiacetal]] intermediates, which are in general short-lived and relatively unstable "mid-stage" compounds that react with other molecules present to form more stable polymeric compounds.
-Polymerization that is not sufficiently moderated and proceeds at a fast rate can be very hazardous. This phenomenon is known as [[hazardous polymerization]] and can cause fires and explosions.
 ==<span class="anchor" id="Step-growth v chain growth polymerization"></span>Step-growth vs. chain-growth polymerization==
 Step-growth and chain-growth are the  main classes of polymerization reaction mechanisms.  The former is often easier to implement but requires precise control of stoichiometry.  The latter more reliably affords high molecular-weight polymers, but only applies to certain monomers.
+[[File:Polymerization classification ENmod.png|thumb|A classification of the polymerization reactions|alt=|440x440px]]
 ===Step-growth===
 {{Main|Step-growth polymerization}}
-In step-growth (or step) polymerization, pairs of reactants, of any lengths, combine at each step to form a longer polymer molecule. The [[Molar mass distribution#Number average molar mass|average molar mass]] increases slowly. Long chains form only late in the reaction.<ref name=Allcock>Allcock H.R., Lampe F.W. and Mark J.F. ''Contemporary Polymer Chemistry'' (3rd ed. Pearson Prentice-Hall 2003), p.29-30 {{ISBN|0-13-065056-0}}</ref><ref name=Fried>{{cite book |last1=Fried |first1=Joel R. |title=Polymer Science and Technology |date=2003 |publisher=Prentice-Hall |isbn=0-13-018168-4 |page=23 |edition=2nd}}</ref>
+In step-growth (or step) polymerization, pairs of reactants, of any lengths, combine at each step to form a longer polymer molecule. The [[Molar mass distribution#Number average molar mass|average molar mass]] increases slowly. Long chains form only late in the reaction.<ref name=":0">{{Cite book |last1=Allcock |first1=H. R. |url= |title=Contemporary polymer chemistry. |last2=Lampe |first2=Frederick Walter |last3=Mark |first3=James E. |publisher=Pearson/Prentice Hall |others=Frederick Walter Lampe, James E. Mark |year=2003 |isbn=0-13-065056-0 |edition=3rd |location=Upper Saddle River, N.J. |pages=29–30 |oclc=51096012}}</ref><ref name=":1">{{Cite book |last=Fried |first=Joel R. |url= |title=Polymer science and technology |publisher=Prentice Hall Professional Technical Reference |year=2003 |isbn=0-13-018168-4 |edition=2nd |location=Upper Saddle River, NJ |pages=23 |oclc=51769096}}</ref>
-Step-growth polymers are formed by independent reaction steps between functional groups of monomer units, usually containing [[heteroatoms]] such as nitrogen or oxygen. Most step-growth polymers are also classified as [[condensation polymer]]s, since a small molecule such as water is lost when the polymer chain is lengthened. For example, [[polyester]] chains grow by reaction of [[alcohol]] and [[carboxylic acid]] groups to form [[ester]] links with loss of water. However, there are exceptions; for example [[polyurethane]]s are step-growth polymers formed from [[isocyanate]] and alcohol bifunctional monomers) without loss of water or other volatile molecules, and are classified as [[addition polymer]]s rather than condensation polymers.
+Step-growth polymers are formed by independent reaction steps between functional groups of monomer units, usually containing [[heteroatoms]] such as nitrogen or oxygen. Most step-growth polymers are also classified as [[condensation polymer]]s, since a small molecule such as water is lost when the polymer chain is lengthened. For example, [[polyester]] chains grow by reaction of [[Alcohol (chemistry)|alcohol]] and [[carboxylic acid]] groups to form [[ester]] links with loss of water. However, there are exceptions; for example [[polyurethane]]s are step-growth polymers formed from [[isocyanate]] and alcohol bifunctional monomers) without loss of water or other volatile molecules, and are classified as [[addition polymer]]s rather than condensation polymers.
 Step-growth polymers increase in molecular weight at a very slow rate at lower conversions and reach moderately high molecular weights only at very high conversion (i.e., >95%).  '''Solid state polymerization''' to afford polyamides (e.g., nylons) is an example of step-growth polymerization.<ref name=ullmannC2>{{Ullmann |doi=10.1002/14356007.a21_487.pub3|title=Polyethylene|year=2014|last1=Jeremic|first1=Dusan|pages=1–42|isbn=9783527306732}}</ref>
@@ Line 43: / Line 50: @@
 ===Chain-growth===
 {{Main|Chain-growth polymerization}}
-In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a [[free radical]], [[cation]], or [[anion]]. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers. Long chains are formed from the beginning of the reaction.<ref name=Allcock/><ref name=Fried/>
+In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a [[free radical]], [[cation]], or [[anion]]. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers. Long chains are formed from the beginning of the reaction.<ref name=":0" /><ref name=":1" />
-Chain-growth polymerization (or addition polymerization) involves the linking together of unsaturated monomers, especially containing carbon-carbon [[double bonds]]. The pi-bond is lost by formation of a new sigma bond. Chain-growth polymerization is involved in the manufacture of polymers such as [[polyethylene]], [[polypropylene]], [[polyvinyl chloride]] (PVC), [[acrylate]]. In these cases, the alkenes RCH=CH<sub>2</sub> are converted to high molecular weight alkanes (-RCHCH<sub>2</sub>-)<sub>n</sub>  (R = H, CH<sub>3</sub>, Cl, CO<sub>2</sub>CH<sub>3</sub>).
+Chain-growth polymerization (or addition polymerization) involves the linking together of unsaturated monomers, especially containing carbon-carbon [[double bonds]]. The pi-bond is lost by formation of a new sigma bond. Chain-growth polymerization is involved in the manufacture of polymers such as [[polyethylene]], [[polypropylene]], [[polyvinyl chloride]] (PVC), and [[acrylate]]. In these cases, the alkenes RCH=CH<sub>2</sub> are converted to high molecular weight alkanes (-RCHCH<sub>2</sub>-)<sub>n</sub>  (R = H, CH<sub>3</sub>, Cl, CO<sub>2</sub>CH<sub>3</sub>).
 Other forms of chain growth polymerization include [[cationic addition polymerization]] and [[anionic addition polymerization]]. A special case of chain-growth polymerization leads to [[living polymerization]]. [[Ziegler–Natta polymerization]] allows considerable control of [[Branching (polymer chemistry)|polymer branching]].
-[[Image:Ethylene polymerization.png|thumb|right|Polymerization of [[ethylene]]]]
+[[File:Ethylene polymerization.png|thumb|right|Polymerization of [[ethylene]]]]
 Diverse methods are employed to manipulate the initiation, propagation, and termination rates during chain polymerization. A related issue is temperature control, also called [[heat management]], during these reactions, which are often highly exothermic. For example, for the polymerization of ethylene, 93.6 kJ of energy are released per mole of monomer.<ref name=ullmannC2/>
@@ Line 56: / Line 63: @@
 === Photopolymerization ===
-{{main|Photopolymer}}
+{{Main|Photopolymer}}
-Most '''photopolymerization''' reactions are chain-growth polymerizations which are initiated by the absorption of visible<ref>{{Cite journal|last1=McKenzie|first1=Thomas G.|last2=Fu|first2=Qiang|last3=Wong|first3=Edgar H. H.|last4=Dunstan|first4=Dave E.|last5=Qiao|first5=Greg G.|date=2015-06-23|title=Visible Light Mediated Controlled Radical Polymerization in the Absence of Exogenous Radical Sources or Catalysts|journal=Macromolecules|volume=48|issue=12|pages=3864–3872|doi=10.1021/acs.macromol.5b00965|issn=0024-9297|bibcode=2015MaMol..48.3864M|url=https://figshare.com/articles/journal_contribution/Visible_Light_Mediated_Controlled_Radical_Polymerization_in_the_Absence_of_Exogenous_Radical_Sources_or_Catalysts/2155795/files/3789646.pdf}}</ref> or ultraviolet light. The light may be absorbed either directly by the reactant monomer (''direct'' photopolymerization), or else by a ''photosensitizer'' which absorbs the light and then transfers energy to the monomer. In general only the initiation step differs from that of the ordinary thermal polymerization of the same monomer; subsequent propagation, termination and chain-transfer steps are unchanged.<ref name=ALM>Allcock H.R., Lampe F.W. and Mark J.F. ''Contemporary Polymer Chemistry'' (3rd ed. Pearson Prentice-Hall 2003), chap.5. {{ISBN|0-13-065056-0}}</ref>
+Most '''photopolymerization''' reactions are chain-growth polymerizations which are initiated by the absorption of visible<ref>{{cite journal |last1=McKenzie |first1=Thomas G. |last2=Fu |first2=Qiang |last3=Wong |first3=Edgar H. H. |last4=Dunstan |first4=Dave E. |last5=Qiao |first5=Greg G. |date=2015-06-23 |title=Visible Light Mediated Controlled Radical Polymerization in the Absence of Exogenous Radical Sources or Catalysts |journal=Macromolecules |volume=48 |issue=12 |pages=3864–3872 |doi=10.1021/acs.macromol.5b00965 |issn=0024-9297 |bibcode=2015MaMol..48.3864M |url=https://figshare.com/articles/journal_contribution/2155795/files/3789646.pdf}}</ref> or ultraviolet light. Photopolymerization can also be a step-growth polymerization.<ref>{{Cite journal |last=Kaya |first=Kerem |date=January 2023 |title=A green and fast method for PEDOT: Photoinduced step-growth polymerization of EDOT |url=https://linkinghub.elsevier.com/retrieve/pii/S1381514822003091 |journal=Reactive and Functional Polymers |language=en |volume=182 |pages=105464 |doi=10.1016/j.reactfunctpolym.2022.105464}}</ref> The light may be absorbed either directly by the reactant monomer (''direct'' photopolymerization), or else by a ''photosensitizer'' which absorbs the light and then transfers energy to the monomer. In general, only the initiation step differs from that of the ordinary thermal polymerization of the same monomer; subsequent propagation, termination, and chain-transfer steps are unchanged.<ref name=":0" />
-In step-growth photopolymerization, absorption of light triggers an addition (or condensation) reaction between two comonomers that do not react without light. A propagation cycle is not initiated because each growth step requires the assistance of light.<ref name="Soto 2014">{{cite journal |last=Soto |first=Marc |author2=Sebastián, Rosa María |author3=Marquet, Jordi |year=2014 |title=Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols |journal=J. Org. Chem. |volume=79 |issue= 11|pages=5019–5027 |doi=10.1021/jo5005789 |pmid=24820955 }}</ref>
+In step-growth photopolymerization, absorption of light triggers an addition (or condensation) reaction between two comonomers that do not react without light. A propagation cycle is not initiated because each growth step requires the assistance of light.<ref name="Soto 2014">{{cite journal |last=Soto |first=Marc |author2=Sebastián, Rosa María |author3=Marquet, Jordi |year=2014 |title=Photochemical Activation of Extremely Weak Nucleophiles: Highly Fluorinated Urethanes and Polyurethanes from Polyfluoro Alcohols |journal=J. Org. Chem. |volume=79 |issue=11 |pages=5019–5027 |doi=10.1021/jo5005789 |pmid=24820955}}</ref>
-Photopolymerization can be used as a photographic or printing process, because polymerization only occurs in regions which have been exposed to light. Unreacted monomer can be removed from unexposed regions, leaving a relief polymeric image.<ref name=ALM/> Several forms of [[3D printing#Photopolymerization|3D printing]]—including layer-by-layer [[stereolithography]] and
+Photopolymerization can be used as a photographic or printing process because polymerization only occurs in regions which have been exposed to light. Unreacted monomer can be removed from unexposed regions, leaving a relief polymeric image.<ref name=":0" /> Several forms of [[3D printing#Photopolymerization|3D printing]]—including layer-by-layer [[stereolithography]] and [[two-photon absorption#3D photopolymerization|two-photon absorption 3D photopolymerization]]—use photopolymerization.<ref>{{cite journal |title=Additive manufacturing of ceramics from preceramic polymers |journal=Additive Manufacturing |volume=27 |pages=80–90 |doi=10.1016/j.addma.2019.02.012 |date=May 2019 |arxiv=1905.02060 |last1=Wang |first1=Xifan |last2=Schmidt |first2=Franziska |last3=Hanaor |first3=Dorian |last4=Kamm |first4=Paul H. |last5=Li |first5=Shuang |last6=Gurlo |first6=Aleksander |s2cid=104470679}}</ref>
-[[two-photon absorption#3D photopolymerization|two-photon absorption 3D photopolymerization]]—use photopolymerization.<ref>{{cite journal|title=Additive manufacturing of ceramics from preceramic polymers|journal=Additive Manufacturing|volume=27|pages=80–90|doi=10.1016/j.addma.2019.02.012|date=May 2019|arxiv=1905.02060|last1=Wang|first1=Xifan|last2=Schmidt|first2=Franziska|last3=Hanaor|first3=Dorian|last4=Kamm|first4=Paul H.|last5=Li|first5=Shuang|last6=Gurlo|first6=Aleksander|s2cid=104470679}}</ref>
-Multiphoton polymerization using single pulses have also been demonstrated for fabrication of complex structures using a [[digital micromirror device]].<ref>{{Cite journal|last1=Mills|first1=Benjamin|last2=Grant-Jacob|first2=James A|last3=Feinaeugle|first3=Matthias|last4=Eason|first4=Robert W|date=2013-06-17|title=Single-pulse multiphoton polymerization of complex structures using a digital multimirror device|journal=Optics Express|language=EN|volume=21|issue=12|pages=14853–8|doi=10.1364/oe.21.014853|pmid=23787672|issn=1094-4087|bibcode=2013OExpr..2114853M|url=https://eprints.soton.ac.uk/356463/1/oe-21-12-14853.pdf|doi-access=free}}</ref>
+Multiphoton polymerization using single pulses have also been demonstrated for fabrication of complex structures using a [[digital micromirror device]].<ref>{{cite journal |last1=Mills |first1=Benjamin |last2=Grant-Jacob |first2=James A |last3=Feinaeugle |first3=Matthias |last4=Eason |first4=Robert W |date=2013-06-17 |title=Single-pulse multiphoton polymerization of complex structures using a digital multimirror device |journal=Optics Express |language=EN |volume=21 |issue=12 |pages=14853–8 |doi=10.1364/oe.21.014853 |pmid=23787672 |issn=1094-4087 |bibcode=2013OExpr..2114853M |url=https://eprints.soton.ac.uk/356463/1/oe-21-12-14853.pdf |doi-access=free}}</ref>
 ==See also==
-{{div col|colwidth=22em}}
+{{Div col|colwidth=22em}}
-* [[Addition polymer]]
-* [[Condensation polymer]]
 * [[Cross-link]]
+* [[Enzymatic polymerization]]
 * [[In situ polymerization|''In situ'' polymerization]]
 * [[Metallocene]]
@@ Line 79: / Line 84: @@
 * [[Sequence-controlled polymer]]s
 * [[Sol-gel]]
+{{Div col end}}
-* [[Ziegler–Natta catalyst]]
-{{div col end}}
 ==References==
-{{reflist}}
+{{Reflist}}
 {{Authority control}}
 [[Category:Polymerization reactions| ]]