One-step biocatalytic synthesis of linear polyesters with pendant hydroxyl groups

The chemical synthesis of linear polyesters with various hydrophilic functional groups is difficult, involving a multistep reaction pathway and synthesis of a suitable monomer with a protected functional group. A straightforward conventional synthesis from a trifunctional compound, such as glycerol, and a diester or dicarboxylic acid to produce a polyester results in the formation of networks. An alternative approach to the one-step synthesis of aliphatic hydroxyl-substituted polyesters from divinyl adipate (DVA) and various triols has been found by utilizing the intrinsic specificity of an enzyme. The weight average molecular weights of the resulting polyesters vary according to the triol used and range from similar to 3,000 to 14,000 Da. Analysis by MALDI-TOF mass spectrometry has confirmed the presence of a linear polyester with hydroxyl substituents, and there is no evidence for network formation. The pendant groups are 90-95% secondary and 5-10% primary hydroxyl groups. Experimental determination of hydroxyl number verifies that one hydroxyl group is present on each repeat unit of the substituted polyester. By the addition of increasing amounts of 1,4-butanediol to the reaction mixture of glycerol and DVA, predictable and sensitive control of the hydroxyl number can be accomplished.