Biocatalytic “green” synthesis of PEG-based aromatic polyesters: optimization of the substrate and reaction conditions

The condensation copolymerization of a variety of linker molecules with polyethylene glycols (PEGs) of varying molecular weights, catalyzed by lipases under solvent-less conditions is reported. Previously, we reported the lipase-catalyzed condensation polymerization of dimethyl 5-hydroxyisophthalate with polyethylene glycol. Herein we have used a number of linker molecules with hydroxyl, amino, carboxylic acid, alkoxy, amido and alkoxycarbonyl moieties. Also, studies were conducted on the effects of the reaction parameters on the polymerization reactions. The hydrophilic segment was also varied, i.e. polyethylene glycols with molecular weights 300, 600, 900 and 1500 have been used for copolymerization with dimethyl 5-hydroxyisophthalate. The molecular weight of the polyethylene glycol affected the polymer yield and molecular weight. In principle, the method developed is flexible so that it can be used to generate a wide array of functionalized amphiphilic copolymers. In the absence of biocatalytic transformation, such structural control is extremely difficult or currently impossible to obtain.