Polyacrylonitrile

Polyacrylonitrile is made by addition (peroxide-initiated) polymerization of the monomer acrylonitrile (CH2=CHCN, a vinyl monomer carrying a nitrile -CN group), giving the repeating structure -[CH2-CH(CN)]n-. As with other free-radical vinyl polymerizations, a peroxide initiator generates the free radical that starts the chain, which then propagates by successive addition of acrylonitrile units before terminating -- no small molecule is lost, so the repeating unit's elemental composition matches that of the monomer. Its fibre closely resembles wool in feel, warmth and appearance, so it is used as a wool substitute, marketed commerci …