Polymers, liquid crystalline mesomorphic properties

Zhang B, Sun Q, Han M et al (2007) Synthesis and mesomorphic properties of side-chain liquid crystalline ionomers containing sulfonic acid groups. J Appl Polym Sd 104 304-309... 

Crosslinking liquid crystalline polymers yield materials with exceptional properties due to the coupling between elastic properties and mesomorphous behavior. These compounds, especially the mesogenic elastomers, have attracted considerable attention in recent years. Like conventional elastomers, they can sustain very large deformations causing molecular extension and orientation, but they can also exhibit spontaneous distortions, some memory effects, an unusual mechanical response, and coupling between mechanical, optical and electric fields. 

The development of H-bonded complexes is now considered. An influence of UV irradiation on optical properties of low-molecular-weight azobenzene-con-taining material (Fig. 2.4b) has been investigated (Aoki et ah, 2000) on the basis of such interactions. The first observation of photoinduced optical anisotropy in H-bonded complexes of azobenzene dyes and copolymers (Fig. 2.4b) has been recently demonstrated (Medvedev et ah, 2005). In this case, the induced anisotropy was stable, and the maximum dichroic ratio of 2 has been observed. A kinetics of the induction of birefringence (maximum value of ca. 0.01) in one of these complexes is shown in Fig. 2.5. An influence of H-bonding on the mesomorphic and photoorientation properties was recently demonstrated (Cui and Zhao, 2004). In this approach, the amorphous azopyridine side-chain polymer was converted into liquid crystalline polymers through self-assembly with a series of commercially available, aliphatic, and aromatic carboxylic acids (Fig. 2.4d). 

The section commences with monosubstituted ferrocene derivatives, after which the influence of the substitution pattern on the formation and stability of liquid-crystalline phases for disub-stituted ferrocene derivatives will be discussed. Next, the influence of the three-dimensional structure of ferrocene on the mesomorphic properties will be highlighted, optically active ferrocene materials will be described and, finally, ferrocene-containing liquid-crystalline dendrimers will be introduced ferrocene-containing liquid-crystalline polymers will not be reported. Note that a review devoted to ferrocene-containing thermotropic liquid crystals has already been published. ... 

Polymers which exhibit mesomorphic order may have interesting anisotropic properties such as high optical electrical, or mechanical anisotropies. Such polymers may be obtained either by polymerization of a non-mesomorphic monomer in a liquid crystalline solvent (l 2) or by direct polymerization of a mesomorphic monomer in its liquid crystalline state ( 3"9) The organization in the resulting polymers may be improved if the polymerization is done under orienting conditions in electric or magnetic fields or within suitable boundary conditions... 

Hence, the analysis of conformational properties of an extensive class of comb-like polymers with mesogenic side groups showed that the appearance of thermotropic mesomorphic structures in the melts of these polymers is determined by the spontaneous formation of liquid crystalline fragments on a molecular level as a result of the interaction between the side groups. 

In spite of the promising performances of the liquid-crystalline polymers, their use is limited to few practical application. This is due to the high pronounced anisotropy of orientation and properties of LCP processed in the pure state. The apparent contraddiction can be avercome by blending the mesomorphous polymer with ordinary engineering thermoplastics. 

The preparation methods and the novel permselective characteristics of (polymer/LC) composite films have been extensively studied (1-3). Also, various types of (polymer/LC) composite systems have been reported as large area and flexible light-intensity controllable films (4-11). Since thermotropic liquid crystalline polymers (LCPs) with mesogenic side chain groups exhibit both inherent mesomorphic properties of LC and excellent mechanical characteristics of polymeric materials, LCPs... 

In the dry state the NCCs assemble into a percolating network, which is responsible for the great improvement of the mechanical properties of the nanocomposites. The authors started from a 19% (v/v) water dispersion of the NCCs to which the polymer is added to produce the composite. The dispersion used shows birefringence when observed between crossed polars, which appears for NCC concentrations above 5% (w/v) [87]. This birefringence is typical of liquid crystalline phases obtained from suspensions of NCCs, as referred to in Section 8.2. Therefore it is possible to infer that the percolating network referred to by Capadona and coworkers has mesomorphic characteristics, which can be linked with the distinct mechanical properties of the biomimetic composites. 

Synthesis and mesomorphic properties of the first ferrocene-containing side-chain liquid crystalline polymers, 69, obtained by grafting either a 1,1 - or a 1,3-disubstituted ferrocene derivative functionalized by a vinyl group onto a polysiloxane have been reported [155J. These polymers showed enantiotropic SmC and/or SmA mesophases. 

The induction or stabilization of liquid-crystalline phases in binary CT systems, where the donor and the acceptor compounds are rod-shaped, has been utilized in the design of polymers to enhance their mesomorphic properties the combination of mesomorphic properties and those of polymeric systems, e.g., glassy behavior, has attracted interest due to possible applications, for example, in the field of nonlinear optics. Side-chain copolymers with a polyester or polyacrylate backbone containing 4-me-thoxyazobenzene and 4-cyanoazobenzene units, for example, show the formation of an SmA phase with an enhanced mesomorphic temperature range [30]. Similar behavior is observed for copolystyrene derivatives carrying electron-rich donor units (4-methoxy-... 

Marin L, Zabulica A, Sava M (2013) Symmetric liquid crystal dimmers containing a luminescent mesogen synthesis, mesomorphic behavior, and optical properties. Soft Mater 11 32-39 Shukla U, Rao KV, Rakshit AK (2003) Thermotropic liquid-crystalline polymers synthesis, characterization and properties of poly(azomethine esters). J Appl Polym Sci 88 153-160 Shukla SR, Harad AM, Mahato D (2006) Depolymerization of nylon 6 waste fibers. J Appl Polym Sci 100(1) 186-190... 

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