The Liquid Crystalline Phase

Ternary copolyesters containing 30 mol % PHB are partially LC, and those containing over 50 mol % PHB are completely LC [26], 

In copolyesters containing up to 50 mol % PHB, both PET and PEN crystals are formed. In those containing 80-90 mol % PHB, only crystals of PHB are observed [27], 

In this research, commercially available PHB/PET copolyester LCP, PEN and PET were mechanically blended to form the LC phase of the blends. The critical composition of PHB in the PEN and PET forming an LC ternary blend was investigated, and the miscibility and thermal behavior were studied using thermal analysis. The PHB content in the ternary blend was controlled by the amount of PHB/PET copolyester, as a high-molecular-weight PHB homopolyester does 

Poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate) (PET), P(HB80-ET20) (Rodrun 5000) or P(HB60-ET40) (Rodrun 3000) (Unitika Company, Japan) 

Pure PEN required tire highest torque (0.65 Nm), because of its high melt viscosity, and pure PET also needed a high torque (0.38 N m). The torque values of tire ternai-y blends showed similar values below 30 mol % PHB content. However, tire torque values significantly decrease witli increasing PHB content over 40 mol % PHB we propose tliat die high PHB content allows die ternaiy blend to form a EC phase, as confirmed by the moiphology study discussed below. 

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Many of the systems studied are based on [MClJ anion. Neve et al. have extensively studied the formation of liquid-crystalline phases of N-allcylpyridinium salts with allcyl chain lengths of n = 12-18 with tetrahalometalate anions based upon Pd(II) [22] and Cu(II) [23]. In general, the liquid-crystalline phases exhibit lamellar-... 

Martin [25] has also shown that ammonium salts display similar behavior. [Cetyltrimethylammonium]2[ZnCl4], for example, first melts to an Sc-type liquid crystal at 70 °C and then to an S -type mesophase at 160 °C. The broad diffraction features observed in the liquid-crystalline phases are similar to those seen in the original crystal phase and show the retention on melting of some of the order originating from the initial crystal, as shown in Figure 4.1-6. 

Although the liquid crystalline phase of most polybibenzoates usually undergoes a rapid transformation into a three-dimensional crystal, the introduction of oxygen atoms in the spacer of polybibenzoates has been used to prevent or to slow down this transformation. The dynamic mechanical behavior of polybibenzoates with 2, 3, or 4 oxyethylene groups in the spacer (PDEB, PTEB, and PTTB, respectively) is determined by the composition of the spacer [24], as discussed in this section. 

PTEB-Q) to the annealed ones, owing to the presence of the crystalline phase. Moreover, the temperature of the peak increases with the annealing, as well as the broadness of the relaxation. These results suggest that the liquid crystalline phase gives raise to an a relaxation similar to that of amorphous polymers despite the existence of the two-dimensional order characteristic of smectic mesophases, and it changes following the same trend than that of semicrystalline polymers. 

The liquid crystalline phase is called a mesophase and is intermediate between solid and liquid. In this mesophase the molecules show liquid-like long-range behaviour, Le. are essentially disordered, but also some crystal-like... 

All the investigated CBOn compounds show the formation of dimers in the liquid crystalline phases as previously described for the CBn series (see Sect. 2.1.1). 

Iki and Hori discussed the crystal structures of the compounds CPnOB and nOPCB in relation to the mesophase behaviour considering the dimer model proposed by Cladis et al. [99] for this kind of molecule in the liquid crystalline phase. 

Concerning the question whether the detailed knowledge of the structural features in the crystalline state enables the prediction of the type and the properties of the liquid crystalline phases formed from the crystals, the following points should be mentioned. 

From X-ray measurements in the liquid crystalline phase it is impossible to determine the conformation of the molecules in the condensed state. Computer simulations give us information about the molecules internal freedom in vacuum, but the conformations of the molecules in the condensed state can be different because of intermolecular repulsion or attraction. But it may be assumed that the molecular conformations in the solid state are among the most stable conformations of the molecules in the condensed matter and therefore also among the most probable conformations in the liquid crystalline state. Thus, as more crystallo-graphically independent molecules in the unit cell exist, the more we can learn about the internal molecular freedom of the molecules in the condensed state. 

Many of the investigated mesogenic compounds show solid state polymorphism. In order to obtain useful information about the arrangement of the molecules in the mesophase from the X-ray data of the single crystals, it is important to investigate the crystal structure of those solid phase which transforms into the liquid crystalline phase. For instance, only the crystal structures of the low temperature solid phases of the compounds MBBA [138, 139], MHPOBC [159], and T15 [81] could be determined, but the... 

Hopefully with this brief introduction the reader will be able to appreciate fully the chapters which follow and which have been written by experts in the field. The complexity and beauty of the liquid crystalline phase has attracted many able scientists and the applications of liquid crystals in the electronics industry have provided a secure funding base for the subject. This is therefore still a field which is expanding rapidly and many research avenues remain to be explored by newcomers. Perhaps after reading these volumes of Structure and Bonding you will be tempted to join this exciting endeavour. 

The ability of XB to control recognition, self-organization, and self-assembly processes in the different phases of matter is clearly emerging in the literature. This chapter focusses on self-assembly in the solid phase, while the chapters of B. Duncan and A. Legon (in this volume) deal with the liquid crystalline phase and gas phase, respectively. Relatively few papers are reported in the literature on self-assembly processes in solution [66-68,207,208]. Several analytical techniques have been used to detect XB formation, to define its nature, to establish its energetic and geometric characteristics, and to reveal... 

As can be seen in Figure 4a, incorporation of dDAVP in the liquid crystalline phase significantly prolongs the apparent half-life of the peptide. No decline in plasma dDAVP-LI was found during the observation period of five hours, and the level of dDAVP-LI in plasma thus seems to correlate with an apparent zero-order release process of dDAVP. No difference in plasma dDAVP-LI could be found between sc and im administration. 

Such a trimeric structure is almost completely disrupted but present as a monomer for regenerated bR in lipid bilayer of the liquid crystalline phase (Figure 34A and B). As demonstrated in Figure 34B, the 13C NMR... 

In order to investigate the phase transition in the monolayer state, the temperature dependence of the Jt-A isotherm was measured at pH 2. The molecular area at 20 mN rn 1, which is the pressure for the LB transfer of the polymerized monolayer, is plotted as a function of temperature (Figure 2.6). Thermal expansion obviously changes at around 45 °C, indicating that the polymerized monolayer forms a disordered phase above this temperature. The observed temperature (45 °C) can be regarded as the phase transition point from the crystalline phase to the liquid crystalline phase of the polymerized organosilane monolayer. 

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