Cyclopolymerization of dimethyl dipropargylmalonate in supercritical carbon dioxide to give a highly regular polyene containing predominantly five-membered rings.

Poly(dimethyl dipropargylmalonate) synthesized in scCO2 contained more than 95% five-membered rings, i.e., highly regular polyene was produced, which shows carbon dioxide as a reaction medium plays a significant role in determining a highly selective polymer structure.