TY - JOUR A1 - Weh, Lothar T1 - Optical Proof of Mesophase Transitions between Smectic and Nematic Phase of the Side-Group Polyacrylate PaC6 JF - Macromolecular chemistry and physics N2 - The liquid-crystalline side-group polyacrylate PAC6 forms two mesophases in thin layers within the temperature range between 90 and 100 °C. The structures developing by self-organization can be made clearly visible by Schlieren-optical methods. If a low lateral temperature gradient is maintained in the temperature range mentioned above one can simultaneously and abreast observe four phases in PAC6 layers. Both new phases occur between the smectic and the nematic phase. Layer surface deformations arise during this phase transition. They were analyzed with a microscope interferometer. The PAC6 melt shows a considerable change of surface tension in this temperature range. KW - Liquid-crystalline polymers KW - Self-organization KW - Surface structure KW - Temperature gradient KW - Transitions PY - 2003 DO - https://doi.org/10.1002/macp.200350076 SN - 1022-1352 SN - 1521-3935 VL - 204 IS - 18 SP - 2240 EP - 2246 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-2814 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Weh, Lothar T1 - Surface Structures in Thin Polymer Layers Caused by Coupling of Diffusion-Controlled Marangoni Instability and Local Horizontal Temperature Gradient JF - Macromolecular materials and engineering N2 - Surface tension-driven Marangoni convection causes the formation of regular surface structures in drying polymer layers. The shape of the surface structures formed during solvent evaporation depends on layer and interfacial dynamic parameters as well as external factors. The influence of a horizontal radial temperature gradient produced by a point heat source below the polymer layer on the diffusion-controlled Marangoni instability has been studied. In the region of the lateral temperature gradient, radial surface flow coupled with the interfacial instability leads to stripe, ladder, chevron and/or labyrinthine surface structures. KW - Dissipative structures KW - Marangoni convection KW - Polymer layers KW - Surface tension KW - Temperature gradient PY - 2005 DO - https://doi.org/10.1002/mame.200500165 SN - 1438-7492 SN - 1439-2054 VL - 290 IS - 10 SP - 976 EP - 986 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-11318 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -