Mesogenic comb-shaped polymers

Hydrodynamic Properties of Mesogenic Comb-Shaped Polymers... 

The dependences of the intrinsic viscosities [Tl] on the molecular weight are shown in Fig. 3.2, and the parameters K, Kp in Mark-Kuhn equation (3.12) for a series of mesogenic comb-shaped polymers are reported in Tables 3.2 and 3.3. The nature of these dependences (a-b = 0.5) for polymers 2-5 in Table 3.2 and 1-3 in Table 3.3 are in agreement with the constancy of the experimental values of the hydrodynamic invariant Aq = TiQD([T ]M/100) r with respect to the fractions [14]. 

The high intramolecular ordering of the thermotropic mesogenic polymer is also reflected in the strong effect of the solvent on the size of the molecules—the value of the intrinsic viscosity [ti]— in different solvents with presCTvation of the molecular weight of the sample [58]. The intrinsic viscosities [t ] (at 21 C) of mesogenic comb-shaped polymers of the polymethacrylate series in different solvents are reported below ... 

Shibae%, V. R, Kostromin, S. G., and Ivanov, S. A. Photoregulation of the optical properties of comb-shaped polymers with mesogenic side groups and the problems of data recording. Po/ym. Scf. 39, 118 (1997). 

Shibaev VP, Kostromin SG, Ivanov SA. 1996. Comb shaped polymers with mesogenic side groups as electro and photooptical active media. In Shibaev VP, editor. Polymers as Electrooptical and Photo optieal Active Media. Berlin Springer Verlag. 

Here, we will give attention only to the short consideration of the role of three essential stmctural components of comb-shaped polymers - a polymer backbone, a flexible spacer, and a mesogenic group. 

Figire 21 Schematic representations of macromolecules of CL chiral photochromic comb-shaped polymers containing (1) mesogenic, (2) chiral, and (3) photochromic groups. 

The results of a study of the FBF of comb-shaped polymers of the polymethacrylate and polyacrylate series are reported in Tables 3.5 and 3.6. For comparison, the optical characteristics of comb-shaped molecules of similar structure without mesogenic units in the side chains are also reported in these tables. 

The creation of polymer systems which successfully combine the unique properties of low-molecular-weight liquid crystals and high-molecular-weight compounds with their capacity to form films, fibers, and coatings looked promising. However, after the first attempts to solve this problem in the head by synthesis of polymers with mesogenic groups directly bound with the main chain [9-11] (Fig. 6.1a), no less than 5-6 years elapsed before it was proposed in [1-6] that so-called comb-shaped polymers [12] be used as Ae most convenient matrix for synthesis of LC polymers. 

The attempts to obtain LC polymers from inorganic polymers— polyphosphazenes with mesogenic side groups—also merit attention, but the first publications did not report encouraging results. Nevertheless, it is clear that the possibilities of synthesizing new LC comb-shaped polymers are far from exhausted. 

With respect to the role of the configuration of the main chain in the formation of the LC phase, the situation here is close to what takes place in comb-shaped polymers without mesogenic groups a difference in the configurational structure of the macromolecules has little effect on the properties of the mesophase. A comparison of the properties of two samples of LC polymers with the general formula... 

The formation of Williams domains was also observed for comb-shaped polymers in which the structure of the mesogenic groiqrs implies a small negative... 

Figure 4 Schematic representation of macromolecules of different rigidity (a) flexible chains (b) rigid-rod LC polymers (c) main-chain LC polymers with mesogenic groups (d) side-chain LC polymers with mesogenic groups (comb-shaped LC polymers).

Further development of such studies resulted in the self-reinforced plastics based on LC polymers with main-chain mesogenic groups and laid a foundation for the use of comb-shaped LC polymers as new photoactive materials for optics, optoelectronics, photonics, holography, display technology, telecommrmications systems, and other no-less important areas of modem engineering. " ... 

Subsequently, this approach was verified and developed in numerous works performed in many laboratories across the world and has became a commonly accepted method for S)mth-esis of thermotropic LC polymers with side mesogenic groups, or comb-shaped LC polymers. " ... 

A special group of LC polymers is formed by LC ionomers comb-shaped copolymers of mesogen-containing monomer units with unsaturated acids, in which a part of the carboxyl groups is replaced with metal ions. ... 

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