Filled smectics

Note 3 Mesophases can also be induced when the free-volume between the large, irregular molecules of one component is filled by the smaller molecules of the second component. Such mesophases have been called filled smectic mesophases although the term induced is recommended. 

As shown by Pelzl et al. [43, 130-132], whether or not smectic A phases are induced, depends on the shape and length of the rod-like mixing components. This phenomenon can be explained by a filling of the gaps between the aromatic parts of the double-swallow-tailed molecules. Therefore, such induced smectic A phases are called filled smectic A phases [130]. It is legitimate to discuss these filled phases as a new type of guest-host system. Dielectric measurements in pure substances as well as... 

Figure 11. Schematic representation of the molecular packing of double-swaUow-tailed mesogens in smectic and filled smectic A phases.

It should be emphasized here that electron donor-acceptor combinations are not the only ones giving rise to mesophase induction or variation. Similar phase behavior is also known for binary systems composed of suitable proton donor-acceptor pairs due to hydrogen bridging [19, 20], or for combining components of complementary molecular shapes as, for example, in the so-called filled smectics [21]. In... 

Fig. 7 Time-dependence of average number of monomers (m) in the connector between smectic pearls. The simulation data (filled square) are from 8 simulations corresponding to the conditions of Figs. 3 and 6 the solid line is calculated from Eq. 12...

Figure 8.20 Structure and phase sequence of prototypical bent-core mesogen NOBOW (8) are given, along with space-filling model showing one of many conformational minima obtained using MOPAC with AMI force field. With observation by Tokyo Tech group of polar EO switching for B2 smectic phases formed by mesogens of this type, banana LC field was bom. Achiral, polar C2v layer structure, with formation of macroscopic spontaneous helix in polarization field (and concomitant chiral symmetry breaking), was proposed to account for observed EO behavior.

Fig. 25. Arrangement of a smectic A polygonal texture (a) general view of the focal-conic domains filling space efficiently (b) cross-section of the domains showing arrangement of...

On a global scale, the linear viscoelastic behavior of the polymer chains in the nanocomposites, as detected by conventional rheometry, is dramatically altered when the chains are tethered to the surface of the silicate or are in close proximity to the silicate layers as in intercalated nanocomposites. Some of these systems show close analogies to other intrinsically anisotropic materials such as block copolymers and smectic liquid crystalline polymers and provide model systems to understand the dynamics of polymer brushes. Finally, the polymer melt-brushes exhibit intriguing non-linear viscoelastic behavior, which shows strainhardening with a characteric critical strain amplitude that is only a function of the interlayer distance. These results provide complementary information to that obtained for solution brushes using the SFA, and are attributed to chain stretching associated with the space-filling requirements of a melt brush. 

Figure 25.10 Schematic iiiustration of the ceiis for the anisotropic ion conductive measurements. The samples forming homeotropicaiiy aligned monodomains in the smectic liquid crystalline states are filled between electrodes.

Unaligned, disrupted smectics, such as those prepared by quenching from an elevated temperature into the smectic state, are frequently filled with focal conic domains (Sethna and Kleman 1982 Lavrentovich 1986 Larson and Mather 1997). Parabolic focal conic domains can be packed to fill space as shown in Fig. 10-30a. Another packing, which... 

C. The smectic phase was of a special type, namely a filled random mesh smectic phase. The molecular arrangement in this smectic phase can be described as two incompatible segments (mesogens and aliphatic... 

Figure 5. Arrhenius plots for triplet decay of 8a (a), 8b (b), and 8c (c) in the isotropic, nematic, and smectic phases of CCH-4 (O) and CCH-2 ( ). Filled arrows show the transition temperatures for CCH-4 and the open arrows show those for CCH-2 (Data from refs. 31a, 39).

Figure 8. Phase diagram of the Gay-Berne model with the original and the most-studied parameterization (k = 3, k = 5, fi = 2, v = 1) in the density-temperature plane as obtained from computer simulations. Filled diamonds mark simulation results the phase boundaries away from these points are drawn as a guide only. The domains of the thermodynamic stability of the isotropic (/), nematic (N), and smectic (SB) phases are shown. The liquid-vapor critical point is denoted by C. Two-phase regions are shaded. (Reproduced from Ref. 104.)...

Figure 1. Schematic of thin wedge homeotropically filled with smectic liquid crystals.

Fig. 6. However, these two structures are incompatible with one another and cannot co-exist and the molecules still fill space uniformly without forming defects. The matter is resolved by the formation of a periodic ordering of screw dislocations which enables a quasi-helical structure to co-exist with a layered structure. This is achieved by having small blocks/sheets of molecules, which have a local smectic structure, being rotated with respect to one another by a set of screw dislocations, thereby forming a helical structure [15]. As the macroscopic helix is formed with the aid of screw dislocations, the dislocations themselves must be periodic. It is predicted that rows of screw dislocations in the lattice will form grain boundaries in the phase, see Fig. 7, and hence this structurally frustrated phase, which was theoretically predicted by Renn and Lubensky [15], was called the twist grain boundary (TGB).

Fig. 25. The temperature dependence of the layer spacing for the dodecyl (C12) (filled circles), tetradecyl (C14) (open circles), and the hexadecyl (Cie) (triangles) homologues of the (R)-l-methylheptyl 4 -(4-n-alkoxyphenylpropioloyloxy)biphenyl-4-carboxylates (nPlM7 s). The inset shows scans through the layer peak for the tetradecyloxy homologue at temperatures within the smectic C phase (filled circles T = 82.8 °C), the TGBA phase (open circles T = 93.3 °C), and just into the isotropic liquid (triangles T = 97.4 °C)...

Fig. 2.7.3. High resolution specular reflectivity data for 80CB near the peak due to the formation of smectic-like layers near the free surface of the nematic phase. The open circles refer to the scale on the left and the filled circles to the scale on the right. The temperatures T— are (a) 0.10 °C, (Z>) 0.21 C, (c) 0.40 and (

Fig. 5.3.3. X-ray scattering intensity profile from the smectic A phase of 80CB at two reduced temperatures, ( an V an = 9 x 10" (filled circles) and 10 (open circles). The dashed line is the experimental resolution function as would be seen if smectic A had true long-range order. The full lines are the best fits of the theoretical line shape 1 —folded with the resolution function. The values of tj so obtained agree with those calculated from (5.3.12) using experimentally determi ned values of B and k. (Als-Nielson et al. )...

Fig. 5.3.10. Temperature dependence of the elastic constants of the smectic A phase of diethyl 4,4 -azoxydibenzoate determined by ultrasonic velocity measurements open circles, 2 MHz filled circles, 5 MHz triangles, 12 MHz crosses, 20 MHz. (After Miyano and Ketterson. )...

Fig. 5.5.2. Temperature dependence of the susceptibility Of) and the correlation lengths if and for smectic A short-range order in the nematic phase of butoxybenzylidene-octylaniline. Open circles were deduced from X-ray scattering, and filled circles from light scattering. The smectic density wavevector remains...

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