Smectic alkyl chain behavior

Besides differential scanning calorimetry, electron microscopy can also serve for characterizing the mixing behavior of multicomponent vesicular systems. The ripple structure of phospholipids with saturated alkyl chains (also referred to as smectic Bca phase, Fig. 35) is taken to indicate patch formation (immiscibility) in mixed phos-close enough (1-2 nm) lipid molecules are able to diffuse from one membrane to the between the pre- and main-transition of the corresponding phospholipid, electron... 

The stability of the smectic phases is greatly enhanced by the presence of water or alcohols in equimolar amount which have been found to weaken the cation-anion interaction, thus destabilizing the crystal phase. A similar behavior is observed when one of the alkyl chains of the phosphonium cation contains hydroxyl groups. For the same reason, mesophases are not observed with trialkylmethylphosphonium with small anions due to the strong electrostatic interaction. 

There exists a maximum pressure beyond which the smectic A phase disappears (see Fig. Id). The p(7 )-phase boundary nematic-smectic A has an elliptic shape. Reentrant behavior has been found for many systems, and therefore several theoretical treatments have been considered to explain this phenomenon. The most successful is probably the frustrated spin-gas model, which also predicts the sensitivity to the number of carbon atoms in the alkyl chain of the molecule. ... 

The two most extensively studied series of liquid crystal dimers are the a,characteristic behavior of dimers. The acronyms used to refer to these series are BCBOn and m.0n0.m, respectively, in which n refers to the number of methylene groups in the flexible spacer and m that in the terminal alkyl chains. The particular interest in these series arises, in part, because they may be considered to be the dimeric analogues of the 4- -alkyloxy-4 -cyanobiphenyls (nOCB) and the N-(4-n-alkyloxybenzylidene)-4 -n-alkylanilines, respectively, which are probably the most widely studied series of conventional low molar mass liquid crystals. In addition, members of the m.OnO.m series were the first dimers for which extensive smectic polymorphism was observed. 

There have been many papers concerning liquid-crystalline polymers having azobenzenes in their side chains (Figure 14) because of the mesogenic nature of the azo chromophore. Liquid-crystalline polymers incorporating azobenzene moieties in their main chains (30) have also been prepared.102 A family of poly(acrylates) substituted with azobenzenes having chiral alkyl groups (31) showed smectic A as well as cholesteric phases.103 The photochromic behavior... 

Monomers comprising norbomene and Choi moieties with or without alkyl spacers (Fig. 8f) have been synthesized and polymerized by ROMP using second generation Grubbs catalysts [208]. A smectic A mesophase is formed only when the spacer is long enough. The Chol-based ROMP monomer can also be copolymerized with two others, i.e., with a short PEG side chain and a crosslinking tmit, to create a shape memory polymer network [209], where the smectic A mesophase of Choi moieties plays an important role in the shape memory behavior. 

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