Enzyme‐catalyzed synthesis of poly(1,6‐hexanediyl maleate‐co‐fumarate) in organic medium. Study of macrolactone formation in relation to the composition of the initial monomer mixture

The lipase‐catalyzed synthesis of poly(1,6‐hexanediyl maleate‐co‐fumarate) from 1,6‐hexanediol, dimethyl maleate and dimethyl fumarate is described. No secondary reaction involving the double bounds takes place, so that the copolyester composition can be well defined by adjusting the mole fraction of the dimethyl esters in the initial monomer mixture. The average molar masses of the non‐fractionated copolyesters depend on the mole fraction of the dimethyl maleate and are correlated with the amount of macrocycles formed. The possibility that the reaction system obeys a ring‐linear chain equilibrium is discussed. Linear polyester chains and macrolactones are characterized by 1H NMR spectroscopy, steric exclusion chromatography and tonometry. A comparison is made with the homopolyester syntheses which were described in previous works.