Doris Drechsler

Bound rubber morphology and loss tangent properties of carbon-black-filled rubber compounds

The bound rubber phenomenon of carbon-black-filled rubber compounds, which is still an intensively discussed subject, is visualized in this research as a stable nanoscale interphase. Using the novel amplitude and phase-modified atomic force microscope technique, a viscoelastic mapping mode, it becomes possible to quantify mechanical loss tangent properties that are defined as the ratio of loss modulus G″ to storage modulus G′. Imaging loss tangent enables the observation of separated energy dissipation of single constituents within a blend system as well as bound rubber dimensions. Determined with the conventional quantification of insoluble rubber, the amount of bound rubber is correlated with values from the analytical evaluation of loss tangent images. Comparing the loss tangent images and histograms to dynamic mechanical analyses allows the characterization of each single component. On the base of the time-temperature superposition principle, bound rubber dimensions and mechanical properties of filled compounds can be optimized.

Annealing effects on the electrical conductivity of polymerized liquid crystalline 3,4-ethylenedioxythiophene derivatives

Abstract 3,4-Ethylenedioxythiophene derivatives with aromatic, in most cases mesogenic, side groups were synthesized and their liquid crystal behaviour was characterized. These monomers were polymerized oxidatively to charged, electrically conductive polythiophenes. X-ray and atomic force microscopy studies were performed. Films of theses polythiophenes achieved via in situ polymerization were prone to a significant increase of the conductivity by annealing.