ORDER PARAMETERS IN S_A, S_C AND N PHASES BY X-RAY DIFFRACTION

Abstract

X-ray diffraction measurements have been made on the nematic and smectic A phases of three compounds : 408 : N-(p'-butoxybenzylidine)-p-n-octylaniline, TBBA : terephthal-bis-butylaniline, IBPBAC : isobutyl-4-(4'-phenylbenzylideneamino) cinnamate. Additional measurements have been made on the smectic C phase of TBBA. In all cases the distribution function for the orientation of the long molecular axes relative to the director has been determined and compared with the simple mean field theory. Values of < P2 > and < P4 > have also been obtained and for 408 are in excellent agreement with results obtained by other techniques. For the smectic phases order parameters characterising the distribution of the molecules in the layers have been obtained under the assumption of Gaussian distributions and values for the rms displacements < Z2 >1/2 are given

Determination of Orientational Order Parameters of Two Tri-Component Mixtures from Optical Birefringence and X-Ray Diffraction Measurements

“…The peak intensity position which corresponds to χ = 0 was determined from the χ-scan. From the values of I(χ), the distribution function f (β), and the order parameters ( P 2 and P 4 ) was calculated following Leadbetter's expression [25]. For the determination of the experimental f (β) values and hence the order parameters, the azimuthal distribution of the X-ray intensities I(χ) in one quadrant (from χ = 0 to χ = 90 • ) is sufficient.…”

“…5a, b. The angular distribution of the X-ray diffraction intensities for mixtures ABC and ABD were used to determine the order parameters P 2 and P 4 defined by [24,25]: It is to be noted that to determine the order parameters from X-ray diffraction photographs, a χ-scan (i.e. X-ray intensity I(χ) vs. azimuthal angle χ curve) of the outer diffraction arc for χ = 0 to χ = 360 • was first obtained.…”

Orientational Behaviour of the Guest-Host Systems in the Smectic A and Nematic Phases

“…Both (P2) and (Ρ4) can be simultaneously obtained on the basis of X-ray diffraction [19][20][21][22][23], magnetic resonance [25], Raman spectroscopy [25][26][27][28][29][30][31][32] as well as fluorescence depolarization of the dye dissolved in liquid crystalline matrix [7,[10][11][12][13][14][15].…”

Polarization-selective polymerization in a photo-crosslinking monomer film

“…11) ( phases it is well known that they exhibit a higher degree of order compared to the more oen observed nematic phase in liquid crystalline monomers. 11,19,20 Since the polarization-selectivity of the dichroic photoinitiator largely depends on the order of the host, it is expected that in the SmB phase, which exhibits the highest degree of order, a higher polarization-selectivity can be achieved. LC host 2 is a monoacrylate which forms a linear polymer upon polymerization.…”