Accession Number : ADA266676


Title :   Structure/Property Relationships of Siloxane-Based Liquid Crystalline Materials


Descriptive Note : Final rept. Jan 1990-May 1992


Corporate Author : WRIGHT LAB WRIGHT-PATTERSON AFB OH


Personal Author(s) : Bunning, Timothy J ; Klei, Herbert E ; Koberstein, Jeffery T ; Samulski, Edward T ; Adams, W W


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a266676.pdf


Report Date : May 1992


Pagination or Media Count : 317


Abstract : The structure/property relationships of a class of cyclic-siloxane based molecules were investigated. X-ray diffraction and electron microscopy techniques were used to initially investigate commercially available pentamethylcyclopentasiloxane rings with various molar ratios of biphenyl-4- allyloxybenzoate and cholesteryl-4-allyloxybenzoate mesogens attached. Results indicated a strong dependence of the X-ray diffraction patterns on the composition of the mesogens. Three dozen new siloxanes with mesogens were synthesized to investigate the packing behavior in more detail. Variables investigated included siloxane ring size, siloxane shape, leader group length, and mole fraction cholesterol. The phase behavior of these compounds was characterized using polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction including real-time synchrotron experiments. The amount of cholesterol and the leader group length both substantially affected the liquid crystalline packing behavior. Cholesterol served to disrupt the homogeneity of the interdigitated smectic structure while increasing the tendency of the mesophase to layer pack. Lengthening the leader group increased the packing efficiency among mesogens. Certain compounds could be drawn into long, birefringent fibers with the orientation of the mesogens parallel to the fiber axis. The advantage of using cyclic siloxane rings was shown to lie in their processability. Optically clear thin films and fibers were readily obtainable....Liquid crystal, Smectic, Spectroscopy, Cholesteric, X-ray diffraction, Siloxane, Electron microscopy


Descriptors :   *CHEMICAL PROPERTIES , *PHYSICAL PROPERTIES , *THIN FILMS , *MOLECULAR STRUCTURE , *SILOXANES , *LIQUID CRYSTALS , SCANNING , OPTICS , RATIOS , FIBERS , CHROMOPHORES , MATERIALS , ELECTROMAGNETIC PROPERTIES , RESPONSE , THERMAL ANALYSIS , ELECTRON MICROSCOPY , VARIABLES , ALIGNMENT , PHASE , CRYSTALS , X RAY DIFFRACTION , SHAPE , PHOTOCHROMISM , BIPHENYL , SYNCHROTRONS , CALORIMETRY , HOMOGENEITY , RINGS , BIREFRINGENCE , CHOLESTEROL , LENGTH , POLYMERS , MOLECULES , LAYERS , CHEMICALS , REAL TIME , SPECTROSCOPY , SYNTHESIS


Subject Categories : Organic Chemistry
      Physical Chemistry
      Crystallography


Distribution Statement : APPROVED FOR PUBLIC RELEASE