Liquid crystalline polymeric

Special attention should be paid to rheological behavior of liquid crystalline polymeric systems, which although being similar to that of low-molecular liquid crystals, still has some peculiarities. Without going into a detailed discussion of rheological properties, which are described in separate articles and reviews we shall mention some of their features. 

One more distinguishing feature of liquid crystalline polymeric systems is a peculiar dependence of the viscosity on the shear stress (r) when the latter is small. Kulichikhin et al. were the first to note that in the range of small shear stresses the... 

We shall mention here another property of liquid crystalline polymeric systems. As in the case of low-molar mass liquid crystals, when electric and magnetic fields are applied, liquid crstalline domains get oriented along the direction of the field. Rearrangement of a polymer structure under the effect of a magnetic field was demonstrated in for a PBA-dimethylacetamide system. However, the processes of... 

The design and synthesis of new liquid crystalline polymeric materials endowed with intrinsc chirality deserve attention, as chirality can offer probes of the supermolecular structure and a tool for modulating specific responses of the polymers (1). The chemical transformation of preformed thermotropic polymers can add novel opportunities for the realization of various molecular architectures conventionally unfeasible and best suited for mesophase modification. 

Fig. 10. Schematic illustration of supramolecular liquid-crystalline polymeric complexes I side-chain type II main-chain type III combined type and IV network type...

M. K. Bisaria, P. Andrin, M. Abdou, and Y. Cai. Injection moldable conductive aromatic thermoplastic liquid crystalline polymeric compositions. US Patent 6 379 795, assigned to E. 1. du Pont de Nemours and Company (Wilmington, DE), April 30, 2002. 

The possibility of converting light into mechanical energy has been impressively demonstrated with cross-linked liquid-crystalline polymeric systems containing azobenzene groups that were prepared by polymerizing previously aligned mixtures of acrylate 1-AC and diacrylate 2-AC (see Chart 5.10) [51]. 

In the end, one obtains some truly fantastic materials. For instance, the airbags which allow for soft landing of spacecraft on Mars are made of liquid crystalline polymeric fiber called vectran. This must be a truly special material ... 

SOME ELECTRO-OPTICAL PHENOMENA IN COMB-LIKE LIQUID CRYSTALLINE POLYMERIC AZOMETHINES... 

Thermotropic behavior of H-bonded side-chain liquid crystalline polymeric complexes. 

III. Supramolecular Side-Chain Polymers A. Liquid-Crystalline Polymeric Complexes... 

Ionic interactions can be used for the preparation of supramolecular side-chain polymers [109-111], The interactions between -SO and -NH and those between -COO and -NH give liquid-crystalline polymeric complexes. The complex of poly(ethylene oxide)-fc ocfc-poly(L-lysine) and a carboxyl-functionalized hexa-peri-haxabenzocornene (30) shows columnar structures (Figure 23) [109], Polymeric complex 31 forms a stable smectic phase [111], This complex shows... 

The liquid crystalline polymeric fibers exhibit high degree of order and orientation (greater than 0.9) compare to commodity polymeric fibers such as polyester, nylon, and polypropylene. The structure of commodity fibers is highly defective and contains chain folds and low amorphous orientation and typically crystallinity 30-65%, while the crystalline orientation is in the range of 0.9-0.98. 

Density measurements in liquid crystalline polymeric systems have rarely been reported. Density scans of A/N transitions in liquid crystalline side-chain polysiloxanes [147] and of N/ls transitions in side-chain polysiloxanes and polymethacrylates [273] have been published. Increased densities and lower expansion coefficients compared with corresponding low molecular weight model systems were found, and a van der Waals analysis has been given [273]. One main-ehain polybenzoate was tested in solution [274]. 

Liquid-crystalline polymeric supramolecu-lar species 23 has been prepared by the association of bifunctional H-bonding components [41, 42]. These bifunctional individual components were derived from l(+), d(-), and meso (M) tartaric acids, respectively. It is interesting that the liquid-crystalline phases of the polymeric complexes consisting of chiral species are more stable than those of polymers consisting of meso components. The complex based on l-(+)-tartaric acids shows a mesophase from room temperature to 254 °C, while the mesophase... 

FIGURE 4.8 The molecular structure of Kevlar (polyparaphenylene tere-phthalamide), an extremely strong liquid crystalline polymeric material used in the manufacture of bulletproof vests. 

Lee JW, Jin J (2003) Formation of gold nanoparticles within a liquid crystalline polymeric matrix. J Nanosci Nanotechnol 3 219-221... 

Waigh TA, Perry AP, Riekel C, Gidley MJ, Donald AM, (1998) Chiral side-chain liquid-crystalline polymeric properties of starch , Macromolecules, v31 n22 7980-7984. 

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