THE STRUCTURE OF POLY(D-(-)-BETA-HYDROXYBUTYBUTYRATE)- A REFINEMENT BASED ON THE RIETVELD METHOD

The crystal structure of optically active microbial poly(D(-)-beta-hydroxybutyrate) has been refined with the Rietveld whole-fitting method applied to powder X-ray diffraction data. This natually occurring polymer gives rise to a very crystalline phase and therefore to very detailed and resolved powder profiles. Reliability of the refinement is discussed in relation to results obtained from previous studies on oriented-fiber diffraction patterns. The conclusion is that well-detailed powder profile data are highly discriminatory toward structural models not very dissimilar from each other. This result is considered an encouraging step toward a more general assessment of the accuracy of structural parameters obtained from best fitting of powder X-ray diffraction profiles.