We have made the first observations of the lyotropic cholesteric liquid crystal state of polyisocyanates, in which a synthetically controlled range of the dynamic excesses of one helical sense offer new opportunities for study in the area. In poly((R)-2,6-dimethylheptyl isocyanate) we have generated the cholesteric lyotropic state and studied the pitch as a function of solvent, temperature, and concentration. These data were broken down into entropic, Sq, and enthalpic, Hq, terms and were compared to theoretical predictions. The data for the polyisocyanate were compared to those already known for poly(7-benzyl L-glutamate) and schizophyllail. For all three helical polymers, the sign of S, agrees with Straley's screw model, allowing an absolute assignment of macromolecular helical sense from liquid crystal properties. The nematic phase of the dynamically racemic poly(n-hexyl isocyanate) was doped with a derivative of a steroid and of menthol, and the resulting cholesteric pitch was studied as a function of temperature and dope concentration. The failure to fit these data to theoretical expectations applicable to intrinsically chiral polymers may be due to a sensitivity of the helix sense ratio of the macromolecule to the chiral characteristics of the cholesteric phase.

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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.

Summary.We have demonstrated that optica! circular dichroism (CD) measurements can be carried out on powders suspended in a liquid medium. The refractive indices of the powder and the suspending liquid must be matched, the suspending liquid must not interact significantly with the solid to be measured and must not absorb in the region where the measurements are carried out. Sodium thioantimonate nonahydrate (Na3SbS4-9H20) powders obtained by grinding of levo-or dextrorotatory crystals were found to be excellent examples for the demonstration of this technique. Measurements of the optical rotation for levo-and dextro-rotatory crystals and powders of NaaSbS4"9H20 were also carried out and provided additional characterization of this salt. In the course of developing the CD measurement technique, CD of NaC10 3 and NaBrO3 crystals was also measured.

Soft, low-compression-set and chemically resistant TPEs have been developed from advanced PVC blend technology. These blends have low-temperature flexibility comparable to that of commonly used TPEs and can be made flame-retardant. These new TPEs are suitable for applications in consumer products, automotive, wire and cable insulation, and jacketing. This new class of TPEs, suitable for injection and extrusion operations, represents a significant advance in WC compounding technology.