PHASE-STRUCTURE AND BIODEGRADATION OF THE BACTERIAL POLY(3-HYDROXYBUTYRIC ACID) CHEMOSYNTHETIC POLY(3-HYDROXYPROPIONIC ACID) BLEND/

Two different aliphatic polyesters, bacterially synthesized polyester poly(3-hydroxybutyric acid) [P(3HB)] and chemically synthesized poly(3 -hydoxypropionc acid) [P(3HP)], were blended via solvent casting. By d ifferential scanning calorimetry, polarized optical microscopy, wide-a ngle X-ray diffractometer and dynamic mechanical thermal analytical in strument, thermal and crystallization behavior and dynamic mechanical relaxation of the as-prepared binary blends were systematically studie d. Immiscible properties were ambiguously demonstrated for these blend s over the whole range of constituent composition. Glass transition te mperature and proton spin diffusion times (T-1(H) and T-1 rho(H)) obta ined by the high-resolution solid state C-13 NMR measurements indicate d that the blend system was immiscible not only on an observation scal e of DSC (about 10 nm), but on a T-1(H) scale (several tens of nm). En zymatic biodegradation of the blend samples by extracellular P(3HB)-de polymerase from the bacterium strain A. faecalis T1 showed an approxim ately linear relation between the degradation rate and the component c omposition. In addition, on the basis of biochemical oxygen demand (BO D), pure P(3HP) could not be biodegraded in the river water, while env ironmental biodegradability was confirmed when it presents as one cons titutive component of the binary P(3HB)/P(3HP) blend.