SURFACE TENSIONS AND INTERFACIAL-TENSIONS OF LIQUID-CRYSTALLINE POLYMERS

Surface tensions (gamma(A)) of two side group liquid-crystalline (lc) polymethacrylates and the interfacial tensions (gamma(AB)) between the lc-polymers (LCP) and branched polyethylen respectively polymethylmethacrylat were measured in the isotropic and nematic phase with the pendant-drop method. The surface tensions vs. temperature characteristics show anomalous behavior. The slope is initially negative but changes its sign near the isotropicnematic transition. This behavior is in agreement with surface-tension measurements on low-molar-mass liquid crystals from other authors. The interfacial tension mainly depends on the density difference DELTArho between the two phases, at the phase-transition so we observed a jump of the interface-tension values and a change of the slope. The pendant-drop apparatus contains a video image processing system, that allows to acquire the pendant-drop profile with a personal computer. The program used to analyse the experimental data is based on the ''robust-shape method''. This algorithm allows to calculate both the surface-tensions and the interface-tensions respectively with a personal computer.