Deformation calorimetry of polyurethane block-copolymers

A thermodynamic analysis of the uniaxial stretching of polyurethanes of various compositions and mechanical histories was carried out by using deformation calorimetry. The initial small strain deformations were found to result from the volume elasticity of the hard phase. The intramolecular energy contributions of the soft blocks were estimated. The hard block contributions were shown to depend on their content and on the degree of sample stretching. The predominant role of the soft component is proved to be manifested only in softened samples with a hard block content not exceeding 30%. The thermodynamics of the softening and hysteresis phenomena were studied. The dependence of the deformation mechanism on the hard block content and mechanical history is discussed.The authors express their thanks to Dr. A. R. Korigodsky and Dr. M. P. Letunovsky for the PU samples.     

Alkaloids of Aconitum sajanense I. Structure of acosanine

From the epigeal part of the previously unstudied plantAconitum sajanense we have isolated the new alkaloid acosanine, the structure of which has been established on the basis of spectral characteristics and has been confirmed by a direct comparison with a sample of demethyldelcorine.Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 247–249, March–April, 1992.