Properties of poly‐β‐hydroxybutyrate. I. General considerations concerning the naturally occurring polymer

Poly‐β‐hydroxybutyric acid has been isolated from two bacterial sources by two different procedures. Molecular weight and intrinsic viscosity for the two samples were vastly different. This was blamed on degradation occurring during polymer isolation. An optical rotatory dispersion curve for the high molecular weight sample showed a sharp increase in specific rotation at wavelengths less than 450mμ. From this fact and the reported optical activity of the monomer it is concluded that the polymer is stereo‐regular. X‐ray examination of the “native” and “regenerated” polymer yielded the same crystalline pattern. Electron diffraction and x‐ray data on single crystals of the polymer indicate a fiber repeat of 5.9 A. The value can only be reconciled with some kind of helical conformation in the solid state.