Poly(1,4-cyclopentenylene-5,6-ethylidene-2,3-disodium dicarboxylate)s have been synthesised from the exo,exo-, endo,endo- and exo,endo- isomers of dimethyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylates in a three step process involving ring opening metathesis polymerisation, hydrogenation and hydrolysis. Exo,exo- and endo,exo- pendant functional group stereochemistries were unchanged throughout these processes, whereas, the polymers derived from the endo,endo-monomer underwent fragmentation during hydrogenation and isomerisation during hydrolysis to give to the more stable endoxxo- form of the polymer.