Optical activity measurements in solids 7. Polylactides and poly(β‐hydroxybutyrates)

The optical activities of poly‐(R)‐lactide, poly‐(S)‐lactide, poly(β‐hydroxybutyrate) and two β‐hydroxyvalerate copolymers were measured in solution, as solid powders in suspension, and where possible, as films. Poly‐(+)‐3‐methyl‐1‐pentene was also reinvestigated. In some cases the specific rotation values of powder samples showed significant differences from the values of the solution measurements. The discrepancies of the data observed seem to reflect the local environment of the polymer chains in supermolecular assemblies and consequently the solid state structure(morphology)of the polymers. The circular dichroism (CD) spectra of the polymers were also measured in solution and in the form of their films. For comparison, the CD spectra of the naturally occurring protein casein and of the synthetic polypeptide poly‐(L)‐proline were also measured.