Rose-like texture

The precursor 6 exhibits the enantiotropic nature of chiral nematic (N ), chiral smectic C (SmC ) and chiral smectic I (SmI ) phases. The shell-printed texture of the SmC phase and the rose-like texture of the SmI phase can be clearly seen in Figure 12.6. The thiophene monomers, M2 and M3, show enantiotropic N, SmA and SmC phases. The SmC phase is characteristic of ferroelectricity. The polymers show various mesophases. The phase transition temperatures are summarized in Table 12.4. PI shows an enantiotropic SmA phase. P2 shows enantiotropic SmA, SmC and SmB phases. The fan-shaped texture of the SmA phase and the striated fan-shaped texture of the SmC phase are shown in Figure 12.7. P3 shows an SmA phase in the heating process and SmA and SmX phases in the cooling process. XRD analysis suggests that the SmX phase of P3 might be a higher order smectic phase. 

Figure 12.6 Polarizing optical micrographs of compound 6. (a) Shell-printed texture of chiral smectic C (SmC ) phase at W4°C (b) rose-like texture of chiral smectic I (SmI ) phase at 91 °C. From H. Narihiro, X.-hA. Dai, H. Goto, K. Akagi, Synthesis and properties of polythienylene derivatives with fluorine-containing chiral liquid crystalline substituents (I), Mol. Cryst. Liq. Cryst, 365, 363-371 (2001), reprinted by permission of the publisher (Taylor Francis Ltd, http //www.tandf.co.uk/journals)...

Figure 2 depicts the variation of Scanning Electron Micrographs with crystallization time at different temperatures. At the beginning of the crystallization, the texture of obtained solid phase can be described as an agglomeration of fibrous (Fig. 2a, 2b, 2d). The 110 and 200 reflections are not present in the XRD pattern at this moment. When those reflections appear, the morphology characteristic of MCM-41 described by Tanev et al [6] or Elder et al [12] is detected (Fig,2e, 2f, 2h, 2j). Crystals have variable size and form and very porous surface. Finally when the triphasic mixture composed of hexagonal MCM-41, lamellar MCM-50 and amorphous phase is detected (Fig. 2i, 2k, 21), crystals with a sandy-rose like structure and spheric grains are clearly observed. The sandy-rose crystals belong to the MCM-50 lamellar structure [13] and the spheric grains correspond to the amorphous silica phase. The presence of MCM-50 and amorphous silica is proved by XRD patterns.

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