Conducting polymers liquid crystallinity

Specific blends, which could offer an interesting combination of properties with proper com-patibilization, include PPS/PSE, PEl/PPS, PA/PSE, PA/PEI, and PC/PPS. Patent activity has been noted for most of these blend combinations as well as other selected blends involving engineering polymers as noted in Table 17.3. A number of recent patent and published papers have discussed blends of engineering polymers with various specialty polymers including high temperature polymers, liquid crystalline polymers (LCP s), conductive polymers, and as matrix materials for molecular composites. These will be discussed in the following sections. 

Development of new liquid crystalline (LC) polymeric materials has been a subject of intense interest because of the combination of unusual optical, electrical, and magnetic properties of low-molecular-weight liquid crystals and the mechanical performance and processibility of polymers. Application areas of LC polymers are very diverse, from engineering plastics to LC displays and erasable compact disks. However, the development of conducting and liquid crystalline polymers went on separately in the past in spite of the similarity of the molecular structures of typical main-chain liquid crystals and some conductive polymers. 

The interest in transition metals with <7-bound alkynyl ligands continues, since metal acetyiides are potential nonlinear optical, conducting, or liquid crystalline materials. Their chemistry and applications have been reviewed in 2003 and 2004. Another review dealing on organoiron polymers includes also rigid-rod iron acetyiides. " The chemistry of metal complexes with 1,3-diynes and polyynes was surveyed in 2001. " ... 

Yamamoto, T., Muramatsu, Y., Lee, B.L., Kokubo, H., Sasaki, S., Hasegawa, M., Yagi, T., Kubota, K. Preparation of new main-chain type polyanthraquinones. chemical reactivity, packing stmcture, piezochromism, conductivity, and liquid crystalline and photonic properties of the polymers. Chem. Mater. 15, 4384 393 (2003)... 

As in the study of Luckhurst and collegues discussed in Section 1 and in the experiments conducted on liquid crystalline polymers introduced in Section 2.2, the solute probe molecule used for the NMR investigations was HMB-clig. The rotation technique discussed in Section 1 was used to isotropically distribute the respective z and y components of the susceptibility tensor in a plane perpendicular... 

More recently, Raman spectroscopy has been used to investigate the vibrational spectroscopy of polymer Hquid crystals (46) (see Liquid crystalline materials), the kinetics of polymerization (47) (see Kinetic measurements), synthetic polymers and mbbers (48), and stress and strain in fibers and composites (49) (see Composite materials). The relationship between Raman spectra and the stmcture of conjugated and conducting polymers has been reviewed (50,51). In addition, a general review of ft-Raman studies of polymers has been pubUshed (52). 

Liquid crystalline solutions as such have not yet found any commercial uses, but highly orientated liquid crystal polymer films are used to store information. The liquid crystal melt is held between two conductive glass plates and the side chains are oriented by an electric field to produce a transparent film. The electric field is turned off and the information inscribed on to the film using a laser. The laser has the effect of heating selected areas of the film above the nematic-isotropic transition temperature. These areas thus become isotropic and scatter light when the film is viewed. Such images remain stable below the glass transition temperature of the polymer. 

Liquid crystalline elastomers (LCEs) are composite systems where side chains of a crystalline polymer are cross-linked. Their mesogenic domains can be ordered nematically and undergo a phase transition to a disordered state at a temperature well above the glass-transition temperamre (Tg) of the polymer. Although the phase transition is thermally driven, LCEs demonstrate electrical conductivity and thus can be electrically stimulated." Ratna" has reported contractions of nearly 30% due to the phase transition of acrylate-based LCEs. 

A difference between microcrystallite-based ultrastructure and covalently-crosslinked systems is that microcrystallites melt at specific temperatures, allowing the polymer to be fabricated by heating at modest temperatures. Subsequent cooling of the system below the crystallization temperature allows the physical property advantages of the solid state to become manifest. Liquid crystallinity is also possible if some order is retained in the molten state. Crystalline order not only adds mechanical strength, it also provides opportunities for the appearance of other properties that depend on solid state order—such as electronic conductivity. 

Liquid crystal display technology, 15 113 Liquid crystalline cellulose, 5 384-386 cellulose esters, 5 418 Liquid crystalline conducting polymers (LCCPs), 7 523-524 Liquid crystalline compounds, 15 118 central linkages found in, 15 103 Liquid crystalline materials, 15 81-120 applications of, 15 113-117 availability and safety of, 15 118 in biological systems, 15 111-113 blue phases of, 15 96 bond orientational order of, 15 85 columnar phase of, 15 96 lyotropic liquid crystals, 15 98-101 orientational distribution function and order parameter of, 15 82-85 polymer liquid crystals, 15 107-111 polymorphism in, 15 101-102 positional distribution function and order parameter of, 15 85 structure-property relations in,... 

More recently, Ingram et al. and Wright et al. independently tried to develop new polymer hosts with secondary structures similar to that of a liquid crystalline state, so that ion transport could occur with a higher degree of freedom in the highly oriented environments and become at least partially decoupled from the polymer segmental relaxations. Ion conductivities approaching liquidlike values have been obtained on the condition that the liquid crystalline state could be maintained. However, the incorporation of these novel polymer materials in electrochemical devices remains to be tested. 

Large numbers of functionalized LB films have been prepared. Highly ordered LB films have been formed by the inclusion of surface-active cobaltous phthalocyanine [168] amphiphilic TCNQ was assembled to function as conducting LB films [169] liquid-crystalline LB films, potentially capable of undergoing thermotropic or lyotropic phase transitions [170, 171], have also been generated. Spacer groups introduced into polymeric surfactants (23) helped to stabilize the LB films which they formed by decoupling the motion of pendant polymers (see Fig. 13) [172]. 

The ion conductivities of a range of TPEOCELL complexes with LiCFsSOs were examined by AC impedance spectroscopy from 293-373 K, so that all the complexes remained in the liquid-crystalline state during the measurements [235]. The inorganic salt concentration, indicated by the molar ratio of lithium ions to oxygens in the polymer chain, [Li]/[0], ranged from 0.038 to 0.125. The bulk conductivities were 10-6 Son-1 at ambient temperatures... 

Polymer mixtures have attracted some historical interest,320 as have liquid crystalline polymers.321 Several papers have examined the history of conducting polymers322 and of organic superconductors,323,324 the first having been discovered by Jerome in 1980. 

ICP thin films were used as driving electrodes for polymer-Dispersed Liquid-Crystals (PDLC) display devices. Liquid-crystalline-based display devices, which are commonly made of a liquid-crystal compound sandwiched between two substrates coated with a conducting layer of indium tin oxide (ITO), whose substitution with ICP electrodes could improve the optical and mechanical properties of the display devices. On the way to all-organic displays, PDLC sandwiched between two plastic substrates coated with ICP layers are promising devices for paper-like displays for electronic books which require flexibility, lightness, and low-power consumption. The electro-optical characteristics (transmission properties, drive voltages and switching times) of the PDLC devices depend on the nature of the ICP substrate used [13]. 

In another approach crystallizable side groups like TCNQ and phtha-locyanine were attached to the polymer chain, as well as mesogenic groups leading to liquid crystalline properties. Also side groups with transition metals have been linked in view of macromolecular catalysts, electronically conducting properties, etc. All these functional polymers are at an exploratory stage in laboratories. 

This polymer assumes a smectic B-type liquid-crystalline phase when cast from solution. Then, using LiCF3S03 (LiOTf) as the alkali metal salt (Li/O = 0.4), a conductivity in excess of 1 x 10 2 Q m l is achieved at room temperature, the amorphous EO matrix effectively remaining above its Tg. The molecular architecture of the whole structure is depicted in Fig. 8.9. 

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