Linear aliphatic polyesters whose structure is made of short polyethylene glycol (PEG) segments connected along the chain by malonate units were synthesized from two PEG- containing macrolactones: 15,15-dimethyl-1,4,7,10,13-pentaoxacyclohexadecane-14, 16-dione (1) and 5,8,11,14,17-pentaoxaspiro[2,15]octadecane-4,18-dione (2). Anionic ring-opening polymerization conditions using either thiophenolates or a p-nitrophenolate as initiators yielded poly(ether-ester)s of low to moderate molecular weights, with broad molecular weight distributions. When the monomer also contains an activated cyclopro- pane unit of the cyclopropane-1,1-dicarboxylate type (such as in 2) and harsher polymer- ization conditions are used (higher temperatures and bulkier counterions), opening of the cyclopropyl ring can compete with the dilactone polymerization, providing access to cross- linked materials.