The synthesis of isosorbide aliphatic polyesters is demonstrated by the use of Novozym 435, a catalyst consisting of Candida antarctica lipase B immobilized on a macroporous support. Several experimental procedures were tested and azeotropic distillation was most effective in removing low mass byproduct. Furthermore, the use of diethyl ester derivatives of diacid comonomers gave isosorbide copolyesters with highest isolated yield and molecular weights. The length of the diacid aliphatic chain was less restrictive, but with a clear preference for longer aliphatic chains. The molecular mass values of the obtained products were equivalent or higher than those obtained by nonenzymatic polymerizations, a clear illustration of the potential of enzymatic over conventional catalysis. The ability of Novozym 435 to catalyze the synthesis of isosorbide polyester with weight-average molecular weights in excess of 40 000 Da was unexpected given that isosorbide has two chemically distinct secondary hydroxyl groups. This is the first example in which isosorbide polyesters were synthesized by enzyme catalysis, opening a large array of possibilities for this important class of biomass-derived building blocks. Because these polymers are potential biomaterials, the total absence of conventional Lewis acid catalyst residues represents a major improvement in the toxicity of the material.

Juais, D. Production of polymers derived from renewable sources by enzyme catalysis. 2009. 116p. Masters Thesis-Graduate Program in Chemistry.