Side-chain Liquid Crystalline Polymer

Keywords Liquid crystal Liquid-crystalline polymer Side-chain polymer Ion-conductor Semiconductor... 

Combinations with Liquid Crystais. Because polymeric photorefraction is greatly enhanced by the fast reorientation of the nonlinear optical component, many researchers have investigated the use of liquid crystals as ingredients in polymer-composite photorefractives (149-152). Readers looking for a more detailed understanding of liquid crystalline polymers should also see Liquid Crystalline Polymers, Side-Chain. A major advantage with these materials is that... 

C Wang, H Fei, Y Qiu, Y Yang, Z Wei, Y Tian, Y Chen, and Y Zhao, Photoinduced birefringence and reversible optical storage in liquid-crystalline azobenzene side-chain polymers, Appl. Phys. Lett., 74 19-21, 1999. 

Blinov, L. M., Kozlovsky, M. V., Ozaki, M., Skarp, K., and Yoshino, K. Photoinduced diefaroism and optical anisotropy in a liquid crystalline azobenzene side-chain polymer caused by anisotropic angular distribution of trans and cis isomers./. Appl. Phys. 84, 3860 (1998). 

Cyclic liquid crystalline siloxanes can be considered as a class of the liquid crystalline (LC) side-chain polymers with a low degree of polymerization. 

A. S. Angeloni, D. Caretti, C. Cariini, E. ChieUini, G. Galli, A. Altoare, R. Solaro, and M. Laus, Photochromic liquid-crystalline polymers. Main chain and side chain polymers containing azobenzene mesogens, Liq. Cryst. 4, 513-527 (1989). 

A block copolymer composed of liquid crystalline polymer (LCP) segments or that composed of segments having an LCP unit in their main chain or side chain was synthesized [67,68]. The latter showed partial compatibility and second-phase separation even when in a melt liquid crystalline state. 

Shear modulus, polyamide, 138 Sheet molding compounds (SMCs), 30 Shoe sole products, 205 Shore hardness gauge, 243 Side-chain liquid crystalline polymers, 49 Side reactions, in transition metal coupling, 477... 

Optical and electro-optical behavior of side-chain liquid crystalline polymers are described 350-351>. The effect of flexible siloxane spacers on the phase properties and electric field effects were determined. Rheological properties of siloxane containing liquid crystalline side-chain polymers were studied as a function of shear rate and temperature 352). The effect of cooling rate on the alignment of a siloxane based side-chain liquid crystalline copolymer was investigated 353). It was shown that the dielectric relaxation behavior of the polymers varied in a systematic manner with the rate at which the material was cooled from its isotropic phase. 

Incorporation of flexible siloxane spacers into side chain or main chain liquid crystalline polymers have been shown to drastically reduce the transition temperatures 255,267,271,272,277) anc[ aiso increase the response time of the resultant systems to the applied thermal, optical or electrical fields 350-353>. In addition, siloxanes also provided elastomeric properties and improved the processibility (solution or melt) of the resulting liquid crystalline copolymers. 

The same flow-aligning side-chain liquid crystalline polymer has been studied [43] in extensional flow using a rheo-NMR method in which selective excitation of... 

Effect of the Polymer Backbone on the Thermotropic Behavior of Side-Chain Liquid Crystalline Polymers... 

A review of the literature demonstrates some trends concerning the effect of the polymer backbone on the thermotropic behavior of side-chain liquid crystalline polymers. In comparison to low molar mass liquid crystals, the thermal stability of the mesophase increases upon polymerization (3,5,18). However, due to increasing viscosity as the degree of polymerization increases, structural rearrangements are slowed down. Perhaps this is why the isotropization temperature increases up to a critical value as the degree of polymerization increases (18). 

Lastly, it was demonstrated with PPO substituted with a series of alkyl side-chains as we have here, that the glass transition temperature decreases with an increase in the side-chain length (28). At the same time, the Tg s of the more flexible side-chain liquid crystalline polymers investigated to date are always much higher than those of the corresponding polymers without the mesogenic side-chains (3). Therefore, it is quite likely that we may obtain side-chain liquid crystalline polymers of approximately the same Tg from PPO and PECH. 

These results demonstrate that side-chain liquid crystalline polymers can be synthesized by polymer analogous reactions from theoretically any polymer backbone. When the polymer backbone is rigid, as in the case of PPO, a long spacer is required both to decrease the Tg of the parent polymer and to partially decouple the... 

Figure 8 Liquid-crystalline polymers in which the mesomorphic sequences occur in the side-chain (middle), in the chain backbone (top), or in both (bottom) ( combination structures).

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