Side chain with liquid crystalline

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. 

For the small molecular mass ferroelectric liquid crystal when reversing the polarity of the applied electric voltage the molecules rotate locally while their molecular mass centers don t necessarily move accordingly. But for side chain ferroelectric liquid crystalline polymers, as one of the side group ends is confined to backbone, shown in Figure 6.43, the polarity reversion must be accompanied by the movement of their mass centers, which causes a backflow in order to re-distribute the mass centers. Moreover, the side groups may collide with each other. The effect results in the displacement of the backbone. The above effects increase the difficulty of re-orientation and hence increase the viscosity. 

Endo et al. (1992) measured the optical transmission and the polarity-reverse current during the polarity reversion of a side chain ferroelectric liquid crystalline polymer. It was found that both parameters reached peak values at the same time. It was concluded that the rigid core of the side groups responsible for birefringence moves simultaneously with the dipole moment reversion and the latter contributes to the polarity reversion current. The FTIR experiment suggested that the backbone moves when the polarity is reversed. 

Polysiloxanes, polyacrylates, and polymethacrylates are usually used as main-chain components, and alkoxy- or cyano-substitut biphenyls as mesogenic groups. We reported a novel side-chain smectic liquid crystalline polyoxetane with cyano- or fluoro- substituted biphenyl as mesogenic group, and pointed out die importance of the flexibility of the main-chain and the structure of mesogen on the liquid crystalline structure 28-30),... 

Han M, Ichimura K. 2001. Tilt orientation of p methoxyazobenzene side chains in liquid crystalline polymer films by irradiation with nonpolarized light. Macromolecules... 

Liquid crystals (LCs) are described as a fluid phase that flows like a liquid and is oriented in a crystalline manner. LCs are divided into two types thermotropic LCs, where the LC phase transition is dependent on temperature or lyotropic LCs, where the LC phase transition occurs as a function of solvent concentration. To introduce liquid crystallinity to conjugated polymers, LC moieties can be introduced to the polymer side chains for side chain-type liquid crystallinity. On the other hand, designing conjugated polymers with rigid main chain structures with flexible alkyl side chains for solubility enables main chain-type liquid crystallinity. 

Polymers with mesogenic side chains exhibit liquid crystalline behavior which is influenced by the nature of the polymeric backbone and its proximity to the mesogenic group in the side chain. 

The synthesis of side-chain type liquid crystalline elastomer with properties of liquid crystal as well and is first reported by Finkelmarm et al. [52], The synthesis is carried out in one step via hydrosi-lylation reaction in mixture of divinyl dimethyl siloxane ologomers (crosslinking agent), vinyl LC monomer and platinum catalyst. The monomer gets incorporated in the crosslinked elastomer having... 

These materials are compatible with semiconductor technology. Low-oost thin films or waveguiding structures of polymers can be fabricated easily by fomiliar spincoating processes which meet the requirements of integrated nonlinear optics. Polymers and. in particular, side-chain polymers, liquid crystalline or amorphous ones, offer a high potential for molecular engioeering. 

The homopolyestcr of 4-hydroxybcnzoic acid and its copolyestcrs with 6-hydroxy-2-naphthoic acid and with 4,4 -biphenol and tcrephthalic acid are of continuing commercial and academic interest. (1,2) From the applications side, interest stems from the high moduli and high temperature properties of these polymers, while on the fundamental side, interest arises from the main-chain thermotropic liquid crystalline... 

Alam MA, Motoyanagi J, Yamamoto Y et al (2009) Bicontinuous Cubic liquid crystalline materials from discotic molecules a special effect of paraffinic side chains with ionic liquid pendants. J Am Chem Soc 131 17722-17723... 

We chose a polyacrylate with liquid crystalline side chains as shown in Fig. 4. The family of this polymer with different alkyl spacers has been prepared by Ringsdorf and coworkers(25). Recently, they reported an interesting application of the following polymers for image recording(26-28) by means of the photoinduced phase transition principle. 

Block copolymers with liquid crystalline side chains were investigated for the first time by Adams and Gronski in 1989 [60], A polymeranalogous reaction was used to attach the mesogenic side-groups to one of the blocks. In a similar way, block copolymers with azobenzene chromophores were synthesized by Ober et al. [43, 44], In the scope of this review the synthesis of azobenzene-containing block... 

While main-chain type liquid crystalline polymers are made by step-wise polymerizations, side-group type polymers have been synthesized by both step and chain polymerizations of monomers with desired mesogenic side groups. In addition, mesogenic side groups can be introduced to polymers... 

The ease of forming the smectic mesophase by this class of side-group type liquid crystalline polymers has rendered a great possibility in synthesizing polymeric chiral smectic materials useful in non-linear optics, transducers, pyroelectric detectors and display devices (Chapter 6). The first polymer forming a chiral smectic-C phase was synthesized by Shibaev et al. (1984). It has a polymethacrylate main chain, a long polymethylene spacer, and a mesogenic unit attached at the end with a chiral moiety (polymer (3.60)). Since then, a lot of polymers with chiral mesophases have been synthesized and studied (Le Barny and Dubois, 1989). 

The last volume is devoted to polymeric liquid crystals (with chapters about main-chain and side-group thermotropic liquid crystal polymers), amphiphilic liquid crystals, and natural polymers with liquid-crystalline properties. 

Peng B, Johannsmann D, Rtlhe J. 1999. Polymer brushes with liquid crystalline side chains. Macromolecules 32 6759 6766. 

The change in light scattering of conventional polymers with electric and magnetic fields is small. However, much larger effects may be obtained with liquid crystalline systems that have cooperative orientation. As with Kerr effect devices (see Section 4.14), more rapid orientation times desirable for display devices are obtained using low molecular weight or side chain polymer liquid crystals. 

Kerr effects can be very large with liquid crystalline systems where cooperative orientation can occur. This finds use in display devices. Generally, low molecular liquid crystals are employed because of their more rapid orientation times. However, polymers with liquid crystal forming side chains are sometimes used. The advantage of polymers is their mechanical integrity. 

Polymers with side anisodiametric groups modeling the molecular structure of low-molecular liquid crystals csm be obtained either through synthesis of monomers with liquid crystalline (mesogenic) groups with subsequent polymerization or throui chemical attachment of molecules of low-molecular liquid crystalline compounds to a polymer chain by way of polymer-analogous transformations. As can be inferred from the bulk of works dealing with this problem, at present, the first of these two methods is used in most cases. 

Polymers with Liquid Crystalline Side Chains... 

Extensive work has been done in a number of labora-toriesZ-lUL on the synthesis and characterization of several polymers with liquid crystalline side chains. Various of the papers in this monograph deal with various aspects of such polymers containing mesomorphic side chains. A review of the potential applications of such side chain liquid crystalline polymers therefore, will be redundant. 

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