Editing Polymer (section)

====Monomer arrangement in copolymers====
{{Main|Copolymer}}

Copolymers are classified either as statistical copolymers, alternating copolymers, block copolymers, graft copolymers or gradient copolymers. In the schematic figure below, <span style="color:#F46C2C">Ⓐ</span> and <span style="color:#00AAC5">Ⓑ</span> symbolize the two [[repeat unit]]s.

:{| class="wikitable" style="text-align:center; font-size:90%;"
|- class="hintergrundfarbe2"
| [[File:Statistical copolymer 3D.svg|270px|Statistisches Copolymer]]<br />Random copolymer
| [[File:Gradient copolymer 3D.svg|270px|Gradientcopolymer]]<br />Gradient copolymer
| rowspan="2" | [[File:Graft copolymer 3D.svg|270px|Pfropfcopolymer]]<br /> [[Graft copolymer]]
|- class="hintergrundfarbe2"
| [[File:Alternating copolymer 3D.svg|270px|Alternierendes Copolymer]]<br /> Alternating copolymer
| [[File:Block copolymer 3D.svg|250px|Blockcopolymer]]<br /> [[Block copolymer]]
|}

*'''Alternating copolymers''' possess two regularly alternating monomer residues:<ref name="PC14">Painter, p. 14</ref> {{chem|(AB)|n}}. An example is the equimolar copolymer of [[styrene]] and [[maleic anhydride]] formed by free-radical chain-growth polymerization.<ref name=Rudin18>Rudin, p. 18–20</ref> A step-growth copolymer such as [[Nylon 66]] can also be considered a strictly alternating copolymer of diamine and diacid residues, but is often described as a homopolymer with the dimeric residue of one amine and one acid as a repeat unit.<ref name=Cowie104>Cowie, p. 104</ref>
*'''Periodic copolymers''' have more than two species of monomer units in a regular sequence.<ref>{{cite journal |title=Periodic copolymer |url=https://goldbook.iupac.org/terms/view/P04494 |website=IUPAC Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). |year=2014 |publisher=International Union of Pure and Applied Chemistry |doi=10.1351/goldbook.P04494 |access-date=9 April 2020|doi-access=free }}</ref>
*'''Statistical copolymers''' have monomer residues arranged according to a statistical rule. A statistical copolymer in which the probability of finding a particular type of monomer residue at a particular point in the chain is independent of the types of surrounding monomer residue may be referred to as a truly '''random copolymer'''.<ref name="PC15">Painter, p. 15</ref><ref>Sperling, p. 47</ref> For example, the chain-growth copolymer of [[vinyl chloride]] and [[vinyl acetate]] is random.<ref name=Rudin18/>
*'''Block copolymers''' have long sequences of different monomer units.<ref name=Rudin18/><ref name=Cowie104/> Polymers with two or three blocks of two distinct chemical species (e.g., A and B) are called diblock copolymers and triblock copolymers, respectively. Polymers with three blocks, each of a different chemical species (e.g., A, B, and C) are termed triblock terpolymers.
*'''Graft or grafted copolymers''' contain side chains or branches whose repeat units have a different composition or configuration than the main chain.<ref name=Cowie104/> The branches are added on to a preformed main chain macromolecule.<ref name=Rudin18/>

Monomers within a copolymer may be organized along the backbone in a variety of ways. A copolymer containing a controlled arrangement of monomers is called a [[sequence-controlled polymer]].<ref>{{cite journal|last1=Lutz|first1=Jean-François|last2=Ouchi|first2=Makoto|last3=Liu|first3=David R.|last4=Sawamoto|first4=Mitsuo|date=9 August 2013|title=Sequence-Controlled Polymers|journal=Science|language=en|volume=341|issue=6146|pages=1238149|doi=10.1126/science.1238149|issn=0036-8075|pmid=23929982|s2cid=206549042}}</ref> Alternating, periodic and block copolymers are simple examples of [[sequence-controlled polymer]]s.