Showing papers by "University of Paderborn published in 1976"

Pressure Dependence of the Cholesteric Pitch Below and Above a Tricritical Point. Studies on Cholesteryl Myristate and Cholesteryl Oleyl Carbonate Near the Cholesteric-to-Smectic a Phase Transition

Abstract: In order to study the influence of a tricritical point on the untwisting of the cholesteric helix near the phase transition cholesteric-to-smectic A light reflection measurements were carried out with cholesteryl oleyl carbonate (COC) and cholesteryl myristate (CM) up to 4.5 kbar and 95°C. The untwisting of the helix can be observed by the divergence of the wavelength of maximum light reflection λR with pressure in the phase transition region. Whereas the existence of a tricritical point in the phase diagram of COC is already known experimental evidence could be given in the case of CM as well. A comparison of the pressure dependence of λR for COC as well as for CM below and above the tricritical point shows that the divergence of λR with pressure is only little altered by the change in phase transition order.

Polymergebundenes N-(Hexyl)-5-azido-2-nitro-benzoesäureamid; ein photoreaktiver Träger zur Immobilisierung von Liganden Polymer Linked N-(Hexyl)-5-azido-2-nitro-benzoic Acid Amide; a Photoreactive Resin for the Immobilization of Ligands

Abstract: The preparation of a new photochemically-activatable polymer was accomplished by condensation of aminohexyl-6-yl-agarose with the N-hydroxysuccinimide ester of 5-azido-2-nitro-benzoic acid. The latter compound was obtained by diazotization of 5-amino-2-nitro-benzoic acid, exchange of the diazonium group through azide and condensation with N-hydroxysuccinimide. As shown for the photolysis on the monomer level, irradiation of the polymer led to the intermediate formation of a highly reactive nitrene, which is able to immobilize ligands e. g. L-phenylalanine to the polymer.