Polymers liquid crystalline ionic liquids

Figure 11 shows the phase boundary concentration data for aqueous Na salt xanthan [78], fd-virus [24], and TMV [23] with added salt. In all these systems, Ci and cA are very low at low added salt concentration Cs or ionic strength I, and increase with Cs or I. Since such low phase boundary concentrations are not usually observed for neutral liquid-crystalline polymer solutions, it is apparent that polyion electrostatic interactions play an important role in the phase equilibria of these systems. 

The zero-shear viscosity r 0 has been measured for isotropic solutions of various liquid-crystalline polymers over wide ranges of polymer concentration and molecular weight [70,128,132-139]. This quantity is convenient for studying the stiff-chain dynamics in concentrated solution, because its measurement is relatively easy and it is less sensitive to the molecular weight distribution (see below). Here we deal with four stiff-chain polymers well characterized molecu-larly schizophyllan (a triple-helical polysaccharide), xanthan (double-helical ionic polysaccharide), PBLG, and poly (p-phenylene terephthalamide) (PPTA Kevlar). The wormlike chain parameters of these polymers are listed in Tables... 

Smela et al. (2) observed that some conjugated polyelectrolyte dopants caused a layering of polymer chains within a polymer. In other ionic electroactive material additives can be used for crystalline ordering. Such additives may include surfactants and/or liquid crystals. 

Self-standing nanostructured two-dimensional polymer films were prepared by in situ photopolymerization of ionic liquid crystalline monomer 11 that forms homeotropic monodomains of the smectic A phase on a glass plate (Figure 25.4). The film of 12 has a macroscopically oriented layered nanostructure as presented in Figure 25.5. 

Figure 25.4 Molecular structures of ionic liquid crystalline monomer 11 and polymer 12.

Hydrophobically modified polybetaines combine the behavior of zwitterions and amphiphilic polymers. Due to the superposition of repulsive hydrophobic and attractive ionic interactions, they favor the formation of self-organized and (micro)phase-separated systems in solution, at interfaces as well as in the bulk phase. Thus, glasses with liquid-crystalline order, lyotropic mesophases, vesicles, monolayers, and micelles are formed. Particular efforts have been dedicated to hydrophobically modified polyphosphobetaines, as they can be considered as polymeric lipids [5,101,225-228]. One can emphasize that much of the research on polymeric phospholipids was not particularly focused on the betaine behavior, but rather on the understanding of the Upid membrane, and on biomimicking. So, often much was learnt about biology and the life sciences, but little on polybetaines as such. 

Main-Chain Ionic Liquid-Crystalline Polymers... 

When the mesogen moiety is included into the main chain of the polymer, the obtained macromolecule contains inherently rigid units, which usually result in remarkable mechanical properties and thermal stability. Fibers made by these polymers compete with the best ceramic fibers and are far superior to metal fibers [83]. They therefore are ideal candidates as reinforcements for polymer-based composites. However, these materials often have a poor miscibility and adhesion to other polymeric substrates, limiting the range of their applications. This problem basically arises from weak intermolecular interactions either within the liquid-crystalline polymer itself or with the matrix of the composite. Strong ionic... 

The same authors increased the complexity of their systems by introducing in a polyester chain both ionic and chiral chain segments. The series containing both the isosorbide chiral units and the ionic moieties yielded chiral smectic C (SmC ) and chiral smectic B (SmB ) liquid-crystalline phases, exhibiting broken focal-conic texture and schlieren texture. Not surprisingly, the analogous polymer without the chiral units exhibited only the nonchiral SmC mesophase. On the other hand, in this case, the effect of ionic units on the phase behavior was negligible [91]. 

The work described above focused on the introduction of ionic groups into a polymer that, in the neutral state, already exhibited a liquid-crystalline behavior. 

Thermotropic side-chain ionic liquid-crystalline polymers are particularly attractive when the aim is that of merging the liquid-crystalline characteristics of the low molecular weight mesogen side groups with the mechanical properties of the polymeric main chain. It is not surprising, then, that they attracted most of the research efforts in the polymeric ionic liquid crystals field. 

Yoshimi T, Ujiie S (2006) Self-assembly and liquid crystalline properties of ionic polymers and their nonionic family. Macromol Symp 242 290-294... 

Zhang B, Meng F, Tian M et al (2006) Side-chain liquid-crystalline polysUoxanes containing ionic mesogens and cholesterol ester groups. React Funct Polym 66 551-558... 

Ujiie S, Osaka M, Yano Y et al (2000) Ionic liquid crystalline systems with branched or hyperbranched polymers. Kobunshi Ronbimshu 57 797-802... 

Marcos M, Alcala R, Barbera J et al (2008) Photosensitive ionic nematic liquid crystalline complexes based on dendrimers and hyperbranched polymers and a cyanoazobenzene carboxylic acid. Chem Mater 20 5209-5217... 

Pan X, Xiao S, Wang C et al (2009) Photoinduced anisotropy in an azo-containing ionic liquid-crystalline polymer. Opt Commun 282 763-768... 

Functional Liquid-Crystalline Polymers for Ionic and Electronic Conduction... 

Abstract Liquid-crystalline (LC) polymers that exhibit ionic or electronic conduction are described. Anisotropic and efficient transportation of electrons and ions is expected for these materials. The ordered LC nanostructures of LC polymers having ion- or electron-active moieties are important for efficient anisotropic transport. For electron-conductive materials, we focus on side-chain LC polymers. 

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