Synthesis of 1,4,5,6,7,7-hexachloro- and hexabromobicyclo-[2,2,1]-5-heptene-2-carboxylic acid vinyl esters and copolymerization with acrylonitrile

1,4,5,6,7,7-Hexachloro- and hexabromobicyclo-2,2,1]-5-heptene-2-carboxylic acid vinyl esters have been prepared by esterification of the Diels-Alder addition products of hexachloro- and hexabromocyclopentadiene with acrylic acid. These monomers have been copolymerized with acrylonitrile to yield flame-retardant polymers. Copolymers having a chlorine content up to 18.35% or a bromine content up to 6.35% burn, but copolymers containing 25.0% or more of chlorine or 9.83% or more of bromine do not support combustion.