Mirjana Gelo-Pujic

Synthesis of new antioxidant conjugates and their in vitro hydrolysis with Stratum corneum enzymes.

Synopsis

Lipase-mediated direct esterification of a silicone polymer-bearing epoxide functions

Silicone polymers functionalized with acrylate are synthesized industrially using chromium catalysts. To move to green chemistry, biocatalysis was considered an attractive approach. Screening of lipases for the reaction of acrylic acid with epoxide functions attached to a polymer substrate with the silicone backbone (1) led to the selection of two Alcaligenes sp. lipases (QLM and PL), based on their kinetics, availability on an industrial scale and their price. Complete reaction was obtained after 72 h with a two-thirds selectivity (esterification of primary v. secondary hydroxyl group) of 11.0 for PL and 3.6 for QLM (esterification of primary v. secondary hydroxyl group). The structure and bulkiness of the polymer backbone did not influence enzymatic catalysis. Although the lipases showed good thermostability, 60°C was chosen as a compromise between the enzymatic kinetics and a chemical side reaction, polymerization of acrylic acid via Michael addition.