Kernspinlabel-Untersuchungen zur Struktur und Dynamik von flüssigkristallinen Hauptkettenpolymeren

Thermotropic nematic polyesters, specifically deuterated at different positions of the polymer chain, were macroscopically aligned by strong magnetic fields and solid state extrusion. Analysis of the observed 2H NMR spectra was achieved, employing a dynamic NMR model, based on the stochastic Liouville equation. The model considers various double and multiple pulse sequences, recently employed in FT-NMR spectroscopy.

Molecular Scale Study of Domain Boundaries and Frictional Stick-Slip Motion on Lipid Bilayers

A highly 2-dimensional (2D) anisotropic crystal formation of an organic one component lipid bilayer system is presented measured in air by atomic force microscopy. 2D domains with different crystal orientation could be observed. Their molecularly smooth domain boundaries are perceived to be either commensurable or incommensurable lattice joints. Differences in the orientation of the crystal lattice affects dynamic friction on the micrometer scale. High resolution friction images provide stick-slip motions depending on the scan direction in respect to the lattice orientation. It is shown that sliding friction can be determined by an averaged value of the molecular stick-slip motion of the fr…

Tradition and innovation in science

A Commentary on the paper ”Self‐organization of substituted azacrowns based on their discoid and amphiphilic nature„, by C. Mertesdorf and H. Ringsdorf. First published in Liquid Crystals, 5, 1757‐1772 (1989).

Polymeric Monolayers and Liposomes as Models for Biomembranes and Cells

Conventional model membrane systems based on natural lipids usually lack long term stability. Polymer chemistry can help to overcome this disadvantage introducing poly­merizable lipids into these systems. Polymerizable lipids used are diacetylenes, butadienes, acrylates or lipids which can undergo polycondensation.

Hexagonal-columnar mesophases of acylated azacrowns with enhanced stabilities

A series of discotic liquid crystals based on completely acylated macrocyclic oligoamines (azacrowns) has been synthesized. Discotic mesophases could be very highly stabilized by making use of an increased steric hindrance, caused by supplemental lateral meta-substituents which were introduced into the cinnamic acids used as the acylation agents. Employing this method yields compounds exhibiting hexagonal mesophases over a very broad range of more than 300°. Even if very large macrocycles are used as the core of such disc-shaped compounds, enantiotropic mesophases are achieved. Themeta-substituents as well as the size of the azacrowns were varied and their influence on the mesomorphic behav…

Liposomes from α,ω-dipolar amphiphiles with a polymerizable diyne moiety in the hydrophobic chain

Symmetric polymerizable α,ω-dipolar C22-diacetylenes were prepared by oxidative coupling of 10-undecynoic acid and 10-undecynol, respectively, by means of copper II salts in ethanolic solution. 10,12-Docosadiyne-1,22-diphosphate (3)—by reaction of 10,12-docosadiyne-1,22-diol (2) with POCl3—was polymerized in aqueous solution using UV irradiation to form deep blue, thermochromic solutions. By consonication of 3 with cholesterol, monolayer vesicles were formed. This was proven by encapsulation of 6-carboxyfluorescein. These monomeric vesicles were polymerized by UV light to yield stable, deep blue polymeric vesicle suspensions.

Ansiotropy in friction and molecular stick-slip motion

Polymerization of mono- and multilayer forming diacetylenes

Heptadeca-2,4-diine-1-ol and Heptadeca-2,4-diine-1-acid were synthesized and their polymerization behaviour in the solid state was investigated. Both compounds polymerize thermally below the melting point and photochemically under the action of uv-light to form polymers via 1,4-addition to the conjugated triple bonds with a backbone of conjugated double-and triple-bonds. The photoresponse spectra resemble the absorption spectra exhibiting maxima of photoreactivity in the absorption band of the conjugated triple bonds of the monomers.

Einflüsse der Initiatorsubstituenten bei der mit salzhaltigen Ylien initerten Polyinsertionsreaktion auf die Struktur der Polymeren

Die Polymerisation von Methylmethacrylat wurde anionisch mit salzhaltigen Phosphoranen (Ylide) [R3P⊕-CR′R″Li]X⊖ (R=Alkyl, Phenyl; R′=R″=H, Alkyl; X=Br, J) initiiert. Dabei entstehen durch den Einbau des Initiators als Endgruppe polymerisierende Zwitterionen. anhand der Taktizitat des entstehenden Polymethylmethacrylats konnte gezeigt werden, das die Substituenten der endstandigen Phosphoniumgruppe in unpolaren und in polaren Losungsmitteln einen deutlichen Einflus auf die Stereoregulierung der Wachstumsreaktion haben. Aufgrund dieser Beobachtung wird auf die Existenz eines Polybetainsystems geschlossen, das in polaren und unpolaren Losungsmitteln vorliegt und das von den wachsenden Makrozwi…

Polyreactions in ordered systems: Polymerization of octadecyl methacrylate in monolayers at the gas–water interface

The ultraviolet-initiated polymerization of octadecyl methacrylate (ODMA, octadecyl 2-methyl-2-propenoate) as a monomolecular layer at the gas-water interface was studied. The polymerization was carried out at 27°C at the nitrogen-water interface; air inhibits the polymerization. At 27°C the ODMA monolayer exhibits three different states which were characterized by surface pressure-area diagrams and by surface potential measurements. The ODMA monolayer was polymerized under constant surface pressure in the range between 0 and 10 dyne/cm. The polymerization was followed by recording the contraction of the film. The conversion was determined by comparison of the area per monomer unit during p…