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Polarizing Microscope (polarizing + microscope)
Selected AbstractsDetermination of the optical sign of a crystal by a conoscopic methodJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5-1 2010Olga Pikoul To determine the optical sign of an investigated crystal plate, a conoscopic pattern of the latter is changed in an optical system without a polarizing microscope. To change the conoscopic pattern, an auxiliary plane-parallel crystal plate of arbitrary thickness and known optical sign is used. Such a plate, which is either capable of rotation about its vertical axis or fixed at a small angle to the investigated plate, is introduced into the optical system. Upon rotation of the auxiliary crystal plate, isochromatic rings on the conoscopic pattern are offset. Based on the direction of the offset from the centre of the pattern, a conclusion is drawn about the optical sign of the investigated crystal plate. When the auxiliary crystal plate is fixed at a small angle to the investigated plate, either two or three conoscopic patterns are observed on the screen. The optical sign of the investigated crystal plate is determined by the number of conoscopic patterns on the screen. If there are three patterns, then the optical signs of the auxiliary and the investigated plates are the same. If there are two patterns, then the optical signs of the auxiliary and the investigated plates are opposite. [source] Conoscopic method for determination of main refractive indices and thickness of a uniaxial crystal cut out parallel to its optical axisJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2009Leonas Dumitrascu This paper presents a simplified data acquisition and analysis technique for use in determining the main refractive indices and thickness of a uniaxial anisotropic layer cut out parallel to the optical axis, by processing the conoscopic interference figures obtained using a polarizing microscope equipped with a CCD camera. For negative uniaxial crystals, the equations used permit the calculation of the optical sign of the studied material so it is not necessary to insert a quartz wedge into the conoscopic beam. The technique can also be applied to the study of liquid crystal layers in a planar orientation. [source] Synthesis and liquid crystalline properties of new amide-modified poly(1,4-cyclohexanedimethylene terephthalate),JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006P. Deepa Abstract New series of cycloaliphatic poly(ester-amide)s, poly(1,4-cyclohexanedimethyleneterephthalate- co -1,3-cyclohexanedimethylene terephthalamide), were synthesized through solution polymerization route. The compositions of ester/amide units in the copolymers were varied from 0 to 100% by varying the amount of 1,4-cyclohexanedimethanol and 1,3-cyclohexanebis(methylamine) in the feed. The structures of the polymers were confirmed by NMR and FTIR, and the molecular weights were determined by inherent viscosity. The composition analysis by NMR reveals that the reactivity of the diamine toward the acid chlorides is lowered than that of diol, which results in the formation of more ester content in the poly (ester-amides). The thermal analysis indicate that the new poly(ester-amide)s having less than 10 mol % of amide linkages are thermotropic liquid crystalline from 200 to 250 °C and a thread like nematic phases are observed under the polarizing microscope. WXRD studies suggest that the liquid crystalline domains promote the nucleation process in the polyester chains and increases the percent crystallinity of the poly(ester-amide)s. The glass transition temperature of the copolymers initially increases with increase in amide units because of the presence of nematic phases and subsequently follows the Flory,Fox behavior. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 42,52, 2006 [source] Synthesis and Mesomorphic Properties of 4-((4- n -Alkoxy-2, 3, 5, 6-tetrafluorophenyl)ethynyl)phenyl Methoxy-substituted BenzoatesCHINESE JOURNAL OF CHEMISTRY, Issue 5 2001Heng-Feng Li Abstract Two series of 4-methoxybenzoate liquid crystals were synthesized. Their phase transition temperatures were also measured by texture observation in a polarizing microscope and confirmed by DSC. Their mesomorphic properties and fluoro-substitute effect were studied in detail. [source] | ||||||||||