Editing Polyacetylene (section)

==Structure==
{{multiple image
| align = left
| direction = vertical
| header = A segment of ''trans''-polyacetylene
| width = 200
| image1 = Trans-(CH)n.svg
| caption1 = Structural diagram
| image2 = Polyacetylene-3D-balls.png
| caption2 = Ball-and-stick model
}}
Polyacetylene consists of a long chain of [[carbon]] atoms with alternating single and [[double bond]]s between them, each with one [[hydrogen]] atom. The double bonds can have either [[cis–trans isomerism|''cis'' or ''trans'' geometry]]. The controlled synthesis of each [[isomer]] of the polymer, ''cis''-polyacetylene or ''trans''-polyacetylene, can be achieved by changing the temperature at which the reaction is conducted. The ''cis'' form of the polymer is thermodynamically less stable than the ''trans'' isomer. Despite the [[conjugated system|conjugated]] nature of the polyacetylene backbone, not all of the carbon–carbon bonds in the material are equal: a distinct single/double alternation exists.<ref name=Norden/> Each hydrogen atom can be replaced by a [[functional group]]. Substituted polyacetylenes tend to be more rigid than saturated polymers.<ref name=Grubbs/> Furthermore, placing different functional groups as substituents on the polymer backbone leads to a twisted [[conformational isomerism|conformation]] of the polymer chain to interrupt the conjugation.