[[File:General scheme ionic prop.png|thumb|600px|General scheme ionic propagation. Propagating center can be radical, cationic or anionic.]]
In [[polymer chemistry]], '''ring-opening polymerization''' ('''ROP''') is a form of [[chain-growth polymerization]], in which the terminal endterminus of a [[polymer]] chain acts as a [[reactive center]] where furtherattacks [[cyclic compound|cyclic monomers]] can react by opening its ring system andto form a longer polymer chain (see figure). The propagatingreactive center can be [[Radical (chemistry)|radical]], [[anion]]ic or [[cation]]ic. Some cyclic monomers such as [[norbornene]] or [[cyclooctadiene]] can be [[polymerization|polymerized]] to high [[molecular mass|molecular weight]] polymers by using metal [[Catalysis|catalysts]]. ROP continuesis to be the mosta versatile method offor the synthesis of major groups of [[biopolymer]]s, particularly when they are required in quantity.
The driving force for the ringRing-opening of cyclic monomers is viaoften driven by the relief of [[ring strain|bond-angle strain]] or [[steric effects|steric repulsions]] between atoms at the center of a ring. Thus, as is the case for other types of polymerization, the [[enthalpy]] change in ring-opening is negative.<ref name=Young>{{cite book|last=Young|first=Robert J.|title=Introduction to Polymers|year=2011|publisher=CRC Press|location=Boca Raton|isbn=978-0-8493-3929-5}}</ref>
