Preparation of thick films of polymer liquid crystals, homeotropically aligned (polymer chains oriented perpendicularly to the film surface) for specific anisotropic properties – THICKHOMEOPLC

Aligned polymers and networks may present distinct anisotropic properties if high degree of order can be achieved. These properties cover many domains in mechanics, optics, electronics and transport properties. The preparation of polymer films homeotropically aligned (alignment of the polymer chains orthogonal to the film surface) is not trivial, and has never been demonstrated over large thicknesses. A consortium based on BASF-ISIS, Curie Institute and IPCMS propose to develop thick polymer films with this geometry of alignment, by using liquid crystal (LC) materials. Achievement of such materials is of high interest for BASF for a specific industrial application as described into this project. The first and main objective of the project is to manufacture LC polymeric thick films (> 0.1 mm) homeotropically aligned. These films will be prepared from nematic LC monomers having photocrosslinking properties. Anchoring surface effect combined with electrical and/or magnetic poling will be used to achieve the uniform alignment over the whole thickness. The alignment will be stabilised by the photopolymerisation/crosslinking of the monomers. The photopolymerisation will be initiated using an initiator sensitive in the transparency region of the material. The second objective will use the photopolymerisation to pattern the material geometry of alignment, by means of direct photolithographic technique. This patterning will create networks of domains with different mechanical properties that can be used for the fabrication of thermally and/or light-driven actuators with complex 2D or 3D movements.