Polyesters, preparation with enzymes

Enzymes that belong to the class of hydrolases are by far the most frequently-applied enzymes in polymer chemistry and are discussed in Chaps. 3-6. Although hydrolases typically catalyse hydrolysis reactions, in synthetic conditions they have also been used as catalysts for the reverse reaction, i.e. the bond-forming reaction. In particular, lipases emerged as stable and versatile catalysts in water-poor media and have been applied to prepare polyesters, polyamides and polycarbonates, all polymers with great potential in a variety of biomedical applications. 

Furthermore, Kobayashi and co-workers prepared macromers based on polyesters with methacryloyl end groups, using lipases from different origin [72], This was accomplished by the polymerization of DDL in the presence of ethylene glycol methacrylate and vinyl methacrylate. The acryl-enzyme intermediate, formed by reaction of the lipase and the vinyl ester, reacted to terminate propagating chains. 

Research by Matsumura et al (19) describes a different concept whereby lipase-catalysis is used to first degrade polyesters into cylic oligomers. Subsequently, cyclic oligomers formed are then polymerized using the same enzyme-catalyst to prepare high molecular weight polyesters. If such a process could be efficient performed with commercial polyesters, it could function as a method to recycle existing materials into new polyesters. 

Sucrose-containing linear polyesters 19 have been prepared using various enzymes from sucrose 17 and d rboxylic acid diesters 18 [41]. The polycondensation reaction proems in anhydrous pyridine. An alkaliiK protease from a Bacillus sp. catalyzes the esterification of sucrose with bis(2,2,2-trifluoro-ethyladipate) to give a sucrose-containing polyester with M = 2100. The sucrose polyester is highly water soluble and soluUe in polar organic solvents. 

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