Mesomorphic poly

Commonly, polymers with a poly(siloxane) backbone and pendant side chain liquid crystalline groups are used. The side chain liquid crystalline groups are organic complexes with zinc, nickel, or crown ethers. This type of polymers is addressed as mesomorphic poly(siloxane). Side chains based on 4-biphenyl-4-allyloxybenzoate exhibit a special separation performance for racemic compounds. ... 

Aharoni SM, Walsh EK (1979) Rigid backbone polymers. 4. Solution properties of two lyotropic mesomorphic poly(isocyanates). Macromolecules 12 271-276... 

Organized Langmuir films and poly layers of mesomorph cyclolinear polysilox-anes 98MI35. 

Poly(epichlorohydrin) (PECH) and poly(2,6 - dimethyl-1,4-phenylene oxide) (PPO) containing pendant mesogenic units separated form the main chain through spacers of zero to ten methylene units were synthesized and characterized in order to test the "spacer concept." Both polymers were modified by phase transfer catalyzed esterifications of the chloromethyl groups (PECH) or the bromobenzyl groups (brominated PPO) with potassium co -(4-oxybiphenyl) alkanoates and potassium u-(4-methoxy-4-oxybiphenyl)-alk.an oates. While PPO required ten methylene units as a spacer and 4,4 -methoxybiphenyl as mesogen to present thermotropic liquid crystalline mesomorphism,... 

Another example of a conformationally disordered mesomorphic form is the high-temperature phase of trans-1,4-poly(1,3-butadiene).111112 As discussed in Section 2.6, in this phase the disorder corresponds to a statistical succession... 

Mesomorphic forms characterized by conformationally ordered polymer chains packed in lattices with different kinds of lateral disorder have been described for various isotactic and syndiotactic polymers. For instance, for iPP,706 sPP,201 sPS,202 syndiotactic poly(p-methylstyrene) (sPPMS),203 and syndiotactic poly(m -methylstyrene),204 mesomorphic forms have been found. In all of these cases the X-ray fiber diffraction patterns show diffraction confined in well-defined layer lines, indicating order in the conformation of the chains, but broad reflections and diffuse haloes on the equator and on the other layer lines, indicating the presence of disorder in the arrangement of the chain axes as well as the absence of long-range lateral correlations between the chains. 

Most interesting are the effects of salt complexation on the mesomorphic behavior of liquid crystalline crown ethers and liquid crystalline crown ether polymers. Sodium triflate was added to poly(17) [34] and poly(25) (Scheme 14) [39]. The enantiotropic nematic and smectic phases of poly(17) were changed dramatically [40]. With increasing amounts of salt, the clearing temperatures are shifted to higher values while the melting transition increases only slightly. 

Gitsov presented a series of poly(benzyl ether) monodendrimers capable of cation complexation lacking alkyloxy side chains which were non-mesomorphic [93], Laschat followed a different route to obtain disk-like liquid crystals equipped with crown ether moieties. The crown ether was not attached to the mesogenic... 

It is intriguing that even some flexible siloxane polymers form mesomorphic (liquid-crystalline) phases.34 139-166 Some illustrative data are given in Table 4.2. Both poly(diethylsiloxane) and pol y(di-n-propylsiloxane) show two crystalline modifications as well as a mesomorphic phase. (The other major class of semi-inorganic polymers, the polyphosphazenes, are also relatively flexible, and show similarly interesting behavior.)10167... 

The second way of forming nanoparticles of PE-surfs is to use water-soluble block-copolymers with one complexable (ionic) block and one non-com-plexable (nonionic) block. For example, the mesomorphous complexes (solid state) between poly(ethylene oxide)—b-poly(ethylene imine)s and dodecanoic acid can easily by dispersed in water to form nanoparticles [117]. The nanoparticles are of core-shell type and have sizes around 200 nm. Their cores are formed by poly( ethylene imine) dodecanoate while their shells consist of poly(ethylene oxide). It was found that the shapes of the nanoparticles depend on the PEI block. They are, for example, prolate if the PEI is linear and spherical if the PEI is branched. 

A variation of this approach towards redispersible PE-surf nanoparticles was presented by Hentze et al. [130]. Their particle formation procedure is as follows in a first step they prepared core-shell particles with a weakly cross-linked core of poly(styrene) and a shell of poly(ethylene oxide). Secondly, the cores were sulfonated to poly(styrene sulfonate). The cores were complexed with cationic surfactants in the third and final step. They became mesomorphous due to the complexation and show a characteristic length that varies between 2 and 4 nm depending on the alkyl chain length of the surfactant. The mean size of the whole particle is around 400 nm. 

The work presented in the next section concerns the immobilization of retinoic acid by three polyamino acids poly(-L-lysine), poly(-L-arginine) and poly(-L-histidine). The mesomorphous structure of these complexes, which are prepared as nano-particles, has been examined. Then we will report on the physicochemical characteristics of water-soluble complexes formed between PEO-PLL block copolymers and retinoic acid. The structure in the solid-state and solution are discussed. Further the dissociation of the complex when changing the pH is reported. Finally, the immobilization of retinoic acid by PEI with different molecular weights is presented. 

Supramolecular chemistry can be used to create the bent cores that give rise to the symmetry breaking in this family of liquid crystals [139]. The formation of a complex between a calamitic benzoic acid derivative and a bent core terminated with a pyridyl group—neither of which display mesomorphic behaviour—gave rise to a material which displayed SmCP mesophases. The achiral bent cores can also give rise to symmetry breaking when they are attached to flexible polymeric chains, such as poly(siloxane) [140]. 

The study by low-angle X-ray diffraction of AB and ABA block copolymers of styrene and isoprene has allowed Gallot et al.1S9-166) to demonstrate that the existence of mesomorphic structures is a quite general property of block copolymers this property is related to the incompatibility of the macromolecular chains11 and the presence in the molecule of a crystallizable (e.g. poly(ethylene oxide)) block is not the condition that governs the formation of mesomorphic structures. 

The last polymer mentioned in Table 10.9 is poly(p-phenylene terephthalamide). This polymer is spun from its solution in pure sulphuric acid (100%), a dope that exhibits mesomorphic (=liquid crystalline) behaviour it is optically anisotropic and is nematic in character. A number of other polymers, containing rigid elements in the chain have melts of polymer liquid crystals, with a high birefringence and a non-linear optical behaviour in electric fields. 

Studied in ref. [26] is the effect of HFC reaction conditions on the configuration sequences in POCS-4. Since the mesomorphous state in PMCS-4 is formed in stereoregular trans-tactic polymers only [27, 32] and spatial configuration of initial monomers is not always fully preserved in poly-mers, the effect of HFC conditions on transformation of =Si-CI and =Si-OH centers in initial corn-pounds has been studied. The detected fact of cyclosiloxanes partial inversion at Cl atoms substitution at silicon was expected, as reported before [33, 34], More detailed description of reflex correlation was carried out in ref. [35], Symbols and mark projections of units and bonds to the pla-ne perpendicular to the cycle plane. 

Comparison of the data shown in Figure 10 with d values from the diffraction pattern in Figure 11 indicate (Figure 11a) that the mesomorphous component (a narrow reflex), d, is independent of poly(decamethylcyclohexasiloxane) chain tacticity. Hence, irrespective of trans-tactic polymer abi-lity to crystallization, the mesophase temperature range changes insignificantly. At lower tempera-ture of -73°C only, a bending on the temperature dependence curve, d(T), of the mesophase peak occurs. 

Having synthesized a number of complexes of monoalkoxystilbazoles, we explored the effect of using various poly(alkoxy)stilbazoles, given the interesting mesomorphism found in polycatenar mesogens (Section VI,A,3). This work is discussed in detail elsewhere 24). Here, we give an overview of the work to enable the reader to see the overall pattern of liquid-crystal behavior and the issues that arise. 

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