Functional biodegradable polyesters polymerization

The concept of transesterifications was used for polymerization reactions by Hedrick and colleagues [76]. Various biodegradable polyesters were synthesized with the l,3-dimethylimidazol-2-ylidene carbene in THF at 25 °C. Polymers such as poly(e-caprolactone) were obtained with no need of organometallic catalysts, as in classical methods. Poly(ethylene terephthalate) (PET) 97 was synthesized in the ionic liquid 98, which functions as the reaction medium and, at the same time, as a precatalyst that is activated (99) with KOt-Bu. Dimethyl terephthalate (DMT) 100 was condensed with an excess of ethylene glycol 101 to generate 102. The melt condensation of 102 was performed under vacuum using a heating ramp to 280 °C. 

Keywords Aliphatic polyester Biodegradable polymer Functionalized polymer Lactone Living polymerization Macromolecular engineering Ring-opening... 

The polymerization of substituted lactones is an attractive strategy for extending the range of aliphatic polyesters and for tailoring important properties such as biodegradation rate, bioadherence, crystallinity, hydrophilicity, and mechanical properties [100]. Moreover, the substituent can bear a functional group, which can be very useful for the covalent attachment of drugs, probes, or control units. 

Functional polyesters were synthesized through the specific catalysis of lipase, and their properties and functions were evaluated. Enantio- and regioselec-tive polycondensations produced chiral and sugar-containing polyesters, respectively [20,23]. Using lipase catalyst reactive polyesters were conveniently obtained, some of which were crosslinked to biodegradable coatings. Recently, polyester-based biomaterials have been developed by lipase-catalyzed polymerizations. 

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