Enzymatic synthesis of novel aromatic-aliphatic polyesters with increased hydroxyl group density

Abstract

Background: Polyesters with pendant hydroxyl groups are attractive materials which offer additional functionalization points in the polymer chain. In contrast to chemical polycondensation, lipase regioselectivity enables the synthesis of these materials as certain hydroxyl groups remain unaffected during the enzymatic process.

Methods and major results: In this study, a combination of synthesis development and reactor design was used for the enzymatic synthesis of an aliphatic-aromatic polyester with two different classes of pendant hydroxyl groups. Using 2,6-bishydroxy(methyl)-p-cresol as diol in lipase catalyzed polycondensation with adipic acid required the addition of hexane diol as third monomer for polycondensation to take place. Reaction conditions were explored in order to identify the preferred reaction conditions for the incorporation of the aromatic diol and the enhancement of the hydroxyl group density. Post-polymerization with glycerol at low temperature integrated additional aliphatic hydroxyl groups, reduced the polydispersity and increased the end group functionality.

Conclusion: A new material with aromatic building blocks and boosted polymer chain reactivity was obtained, which is suggested to find application in various areas of material development from coatings to adhesives.

Keywords: biocatalysis; enzymatic polymerization; lipase; polyol polyester; process optimization.