NMR characterization of biodegradable polyesters

Biodegradable polyesters obtained by fermentation of Alcaligenes eutrophus are characterized with the aid of H, D, C NMR spectroscopy. Copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate are Bernoullian or mixture of two Bernoullian copolymers depending on fermentation conditions. The reverse reaction was found in the reaction catalyzed by beta-ketothiolase during biosynthetic pathway. The fractional population of gauche and trans conformers around the skeletal CH-CH2 bond is 0.6:0.4 for both poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in chloroform. This result suggests the possibility of formation of isomorphic crystals between copolymers with different composition ratios.