Aza-Michael addition reaction: Post-polymerization modification and preparation of PEI/PEG-based polyester hydrogels from enzymatically synthesized reactive polymers

The utility of aza-Michael addition chemistry for post-polymerization functionalization of enzymatically prepared polyesters is established. For this, itaconate ester and oligoethylene glycol are selected as monomers. A Candida Antarctica lipase B catalyzed polycondensation reaction between the two monomers provides the polyesters, which carry an activated carbon-carbon double bond in the polymer backbone. These electron deficient alkenes represent suitable aza-Michael acceptors and can be engaged in a nucleophilic addition reaction with small molecular mono-amines (aza-Michael donors) to yield functionalized linear polyesters. Employing a polyamine as the aza-Michael donor, on the other hand, results in the formation of hydrophilic polymer networks.