The morphology and domain sizes are reported for a series of thermoplastic polyurethane (TPU) samples with different content in hard segments and the same molecular weight of the soft segments. NMR spin-diffusion experiments were employed with a 1H double-quantum dipolar filter to establish the dominant dimensionality of the spin-diffusion process, which is shown to take place in two and three dimensions for investigated samples. The correlation between mesoscopic and microscopic properties of the TPU samples is discussed. To this purpose the effective volume of the hard domains is correlated with the TPU content of the hard segments and the segmental orientation of the hard segments obtained from the 1H residual dipolar couplings. A semiquantitative model is developed to explain the functional dependence of the residual second van Vleck moment on the effective volume of the hard segments.

No abstract

No abstract

Using a 4‐step scheme, we have synthesized deuterium‐labelled 17α‐hydroxypregnenolone for use as internal standard for an isotope dilution/mass spectrometry plasma assay. 17α‐Hydroxyprogesterone served as starting material. Its 17α‐hydroxygroup was protected by tetrahydropyranylation. Introduction of deuterium by base‐catalyzed enolization and protection of the 3‐hydroxygroup by acetate formation yielded [2,2,4,21,21,21‐2H6]3β,17α‐dihydroxypregna‐3,5‐diene‐20‐one 3‐acetate 17‐tetrahydro‐pyranyl ether. After reductive deuteration of the 3‐ene and removal of the protecting groups [2,2,4,4,21,21,21‐2H7] 17α‐hydroxypregnenolone was obtained. © 1998 John Wiley & Sons, Ltd.

SUMMARY: Cellulose propionate (CP) and plasticized cellulose propionate (CP16) were blended, both in solution and by extrusion, with high molecular weight alternating propene-carbon monoxide copolymers (P-CO). Tensile testing was performed on injection molded blends with a P-CO content of up to 50 wt.-%. The phase behavior was investigated by means of differential scanning calorimetry and electron microscopy. The blends are miscible at compositions up to about 10 wt.-% P-CO. P-CO lowers the melt viscosity of both CP and CP16 and acts as a polymeric plasticizer. Higher amounts of P-CO result in phase separation with domains of P-CO-rich material in the dispersed phase and a continuous CP/CP16-rich phase with a T g even higher than that of pure CP. In this state toughness decreases slightly with increasing P-CO content, while modulus and yield stress increase. After transition into the bicontinuous phase, occurring at a P-CO-content of around 25 wt.-%, toughness and elongation at break increase significantly, while modulus and yield stress decrease.