Liquid crystalline groups

Block copolymers with PS and a polymethacrylate block carrying a liquid crystalline group, PS-b-poly 6-[4-(cyanophenylazo)phenoxy]hexyl methacrylate, were successfully prepared in quantitative yields and with relatively narrow molecular weight distributions (Scheme 5) [18]. The thermotropic liquid crystalline behavior of the copolymers was studied by differential scanning calorimetry. 

VI), were prepared in a mixture containing a crosslinkable monomer having liquid crystalline group side chains. 

The fascination of dendrimers is due essentially to the unique architecture of these molecules and the attendant possibilities of designing well-defined functional (macro)molecules [1], whose functional groups can participate in chemi-cal/physical processes [2], In discussions about functional dendrimers a distinction is made between dendrimers bearing more complex, function-bearing units (such as catalytically active, photoactive units, liquid-crystalline groups) and those whose functionalities serve to control simple chemical/physical molecular properties (such as solubility, viscosity). Since both fulfil a function, the word functional is used as a generic term in the following sections. 

Figure 1.5. A cyclic siloxane framework having a spiropyran and two different liquid crystalline groups attached to it.

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. ... 

Recently, liquid-crystalline polyphenylene derivatives have been synthesized through substitution of a fluorine-containing chiral liquid-crystalline group into side chains, with an aim to develop ferroelectric liquid-crystalline conjugated polymers (Fig. 5 Suda and Akagi 2008). These are attracting interest because they can afford anisotropies in electrical and optical properties when they are macroscopically aligned. This study also elucidated that PPP can be used to prepare new types of polymer materials. 

K. Akagi, M. Narita, R. Toyoshima, H. Shirakawa, Syntheses and properties of polythiophene derivatives with phenylalkyl and liquid crystalline groups. Mol. Cryst. Liq. Cryst., 318, 157-177 (1998). 

K. Akagi, H. Goto, H. Shirakawa, Fenoeleclric liquid crystalline conducting polymers - synthesis and properties of polyacetylene derivatives with chiroptical liquid crystalline groups, Synth. Met., 84, 313-316 (1997). 

H. Goto, X. Dai, T. Ueoka, K. Akagi, Synthesis and properties of polymers from monosubstituted acetylene derivatives bearing ferroelectric liquid crystalline groups, Macromolecules, 37, 4783-4793 (2004). 

All PCH and BPpolymers with liquid crystalline groups in the side chain exhibited fanshaped textures and uniaxial conoscopic patterns in a polarizing optical microscope that are characteristic of the smectic A phase. Typical fan-shaped textures of the polymers prepared with Fe-based and Mo based catalysts are shown in Figure 9-3. 

In the PCH polymer, the enthalpy change due to the smectic to isotropic phase increases with an increase of the terminal alkyl chain length. This means that the liquid crystal state is more stabilized by lengthening the alkyl chain as a terminal moiety of the liquid crystalline group. 

Next, UV-Vis absorption spectra of PCH503A monomer and PPCH503A polymer prepared with Fe-based catalyst were examined. An absorption band at 270 280 nm, observed in both the monomer and the polymer, was assigned to the t ir transition of the benzene moiety of the liquid crystalline group. The absorption band at 320 330 nm in the polymer was assigned to the tt tt transition in... 

Class 9, parallel structures, in which the liquid crystalline groups are in side chains and oriented approximately along the chain backbone. One can distinguish here two subclasses, depending on the location of the mesogenic groups with respect to the backbone, since apparently conformational transitions are difficult ... 

Figure 18.11 shows XRD/X-ray scattering at wide and small angles of ablock copolymer with a liquid crystalline block. This sample is a lamellar block copolymer in which a liquid crystalline (LC) block organizes its smectic phase perpendicular to the lamellar layers. The outer arcs are due to the smaller liquid crystalline layers and the inner arcs are for the lamellar spacings. From this figure, it is possible to get information about layer thickness and the orientation parameter of both the liquid crystalline groups and the lamellae. 

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