Ring-opening polymerization of activated cyclopropanes: polymerization of diethyl 1,1-cyclopropanedicarboxylate by metallic sodium

Summary Diethyl 1,1-cyclopropanedicarboxylate undergoes ring-opening polymerization under anionic conditions. If the cyclopropane is contaminated by diethyl malonate CH₂(COOEt)₂, polymerization can be initiated by metallic sodium. The mechanism of this initiation was found to involve an initial reduction of the malonate by sodium to give the salt (EtOOC)₂CH(^-) Na(⁺) which acts as the real initiator. Poly(diethyl 1,1-cyclopropane dicarboxylate) is soluble in halogenated solvents and was characterized by GPC, IR,¹H- and¹³C-NMR. Molecular weights are low to moderate (typically 10³–10⁴) and are compatible with the low monomer/initiator ratios used in these experiments.Part of this work was presented at the 1993 Spring National ACS Meeting: Penelle J, Clarebout G, Balikdjian I (1993) Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 34(1): 473