New chiral dopants for ferroelectric liquid crystals

New chiral dopants for application in ferroelectric liquid crystal mixtures are presented. They derive from chirally modified biphenylcyclohexylcarbonitriles, lactates and optically active 2-cyano-2-methylalkanoates. Synthetic routes to the new compounds are shown and the physical properties of the new compounds in a non-chiral smectic C host are reported.     

Surface reduction of freely floating smectic bubbles

Elongated freely floating smectic bubbles are observed during their relaxation to equilibrium sphere shape. Unlike soap bubbles that perform weakly damped oscillations into equilibrium, this relaxation is overdamped in smectics by internal structure reorganisation processes. The bubble area reduction of centimetre-sized freely floating bubbles with few nanometres film thickness is recorded with high-speed optical imaging in microgravity and analysed quantitatively. We find a nearly linear reduction of the film area with time, driven by capillary forces and inhibited by smectic layer reorganisations. Characteristic times are in the milliseconds range, with little correlation to the film thickness and bubble size. Instead, the homogeneity of the films and the number and sizes of islands of excess layers that spontaneously form on the films appear to have crucial influence on the dynamics. The efficiency of this process sets the time scale of the film area shrinkage. We discuss the limitations of a minimalistic model that captures smectic layer reorganisation processes.     

Inter-laboratory exercise with an aim to compare methods for 90Sr and 239,240Pu determination in environmental soil samples

In order to deliver reliable results for a multitude of different scenarios, e.g. emergency preparedness, environmental monitoring, nuclear decommissioning and waste management, there is a constant process of method development in the field of radioanalytical chemistry. This work presents the results of a method comparison exercise aimed at quantifying ⁹⁰Sr and ^239,240Pu in environmental soil samples, with the intention of evaluating the performance and applicability of different methods. From the methods examined in this work, recommendations are given in order to find a radioanalytical measurement procedure, for ⁹⁰Sr and ^239,240Pu analysis, which is fit-for-purpose for a particular scenario.

     

Basicity of Very Weak Bases in 1,2‐Dichloroethane

The basicity scale of very weak bases has been set up in 1,2‐dichloroethane to give, for the first time, reliable quantitative insights into the basic properties of weak bases in a low‐polarity solvent. The scale contains 30 compounds, including anilines; phosphanes, and carbonyl bases, such as esters and amides, linked by 53 relative basicity measurements. The scale spans more than 12 pK_ip units, expanding to as low pK_ip values as possible with our current experimental methodology.     

Biorelevant Phosphonic Acids - Protonation and Complexformation Equilibria

Abstract

Various methods of NMR- and PC-controlled titrations were developed in our laboratories. In addition to the by now well-investigated ³¹P- we applied ¹³C-, ¹H-, ¹⁹F- and ¹¹³Cd-NMR controlled titrations. Here we report about the methodical progress and results obtained from acylphophonic acids and corresponding hydroxyimino derivatives - as shown below - which gained interests as potentially anti-viral agents: