Vinyl acetate ($\mathrm{C}{\mathrm{H}}_2=\mathrm{CHOCOC}{\mathrm{H}}_3$)

Vinyl acetate is the ester $\mathrm{C}{\mathrm{H}}_3\mathrm{C}(=\mathrm{O})\mathrm{OCH}=\mathrm{C}{\mathrm{H}}_2$. It combines an acetate ester group with a carbon-carbon double bond.

Addition polymerization consumes the double bond to form polyvinyl acetate. The ester side groups remain attached to the resulting carbon backbone, so polymerization changes connectivity without removing all of the monomer's functional groups.