LC conjugated polymer

Fig. 11.1 Schematic representation of the spontaneous raientation, linear, and helical arrangement of LC conjugated polymers. Reprinted with permission from [17]. Copyright 2013, The...

This novel structural design strategy was further extended to chiral LC conjugated polymers adopting a helical 7r-stacking structure to exhibit dynamic switching of chiroptical functionalities, such as CPL [23]. 

The response time of 1 s in Poly-8 is much smaller than those observed for ordinary LC conjugated polymers (approximately 20-30 min for complete alignment) in N-LC or smectic (Sm LC) phases under an electric field [62]. Note that... 

Since side-chain-type LC polyacetylene derivatives were first synthesized [10-18], various types of LC conjugated polymers have been synthesized and evaluated from the standpoint of their electrical and optical properties [19-46]. Among them, LC aromatic conjugated polymers, including LC polythiophene derivatives, have been of recent interest because they are available for linearly polarized luminescent materials, and also anisotropically conducting materials [28-30, 40-53]. 

However, LC conjugated polymers have an inevitable problem that is frequently encountered during macroscopic alignment, namely, it takes a long time for the LC conjugated polymers to be aligned completely because of the high viscosity inherent to polymeric materials. It is well known that ferroelectric... 

The temperature dependence of the dielectric constant of P2 is shown in Figures 12.9 and 12.10. The dielectric constant (e) suddenly increased in the temperature region of the SmC phase. This is the typical ferroelectric behavior of FLC, because the dielectric constant of the ferroelectric material is inversely proportional to the absolute temperature according to the Curie-Weiss law, i.e. e = C(T — Tq), where C is the Curie constant and Tq is the Curie temperature. At the same time, the dielectric constant increased with decrease in frequency. This tendency is due to the high viscosity of the LC conjugated polymer. 

The dielectric constants of the real (s ) and imaginary (e) parts for P2 were evaluated as a function of frequency. The response time of P2 in the SmC phase at 160 °C was estimated to be 1 s by using the s maximum at 1.1 Hz and the e" inflection at 1.5 Hz. The optical response time of P2 was 1 s with the application of DC 2 kV cm to the polymer-sandwiched ITO glass cell at 150 °C. This value is consistent with that obtained through measurements of the dielectric constants [59-64, 66]. The response time of 1 s for P2 is much smaller than those for ordinary LC conjugated polymers in nematic or smectic phases under an electric field (about 20-30 min for complete alignment). 

Subsequently, small-band gap LC conjugated polymers [11] based on benzonoid and quinoid resonance structures were synthesized. Subsequently, ferroelectric LC (FLC) conjugated polymers [12] consisting of acetylene, thiophene, phenylene, or phenylenevinylene unit cell were synthesized in order to achieve highly quick response to an electric force field during macroscopic alignment. These FLC conjugated polymers, however, will not be further mentioned here and reviewed elsewhere. 

The methods that have been examined for producing polarised EL include the use of liquid crystalline chiral oligomers and polymers. - Promising results have been obtained using conjugated polymers where fluorene makes up the backbone, e.g. (5.6), which was synthesised from the dibromo monomer via Yamamoto coupling. These types of material exhibit LC behaviour at transition temperatures of 100-200 °C, and produce blue polarised EL (425 nm) from thin flhns. °... 

Discotic hydrogen bonded complex of l,3,5-tris(l-alkyl-l//-l,2,3-triazol-4-yl) benzene (TTB) and 10,12-pentacosadiynoic acid (PCDA) can form helical conjugated polymers in an asymmetric reaction field consisting of the lamellar columnar LC phase and CPUL (circular polarized ultraviolet light) stimulus (Fig. 5.15) [76]. 

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. 

The polythiophene (PT) derivative is one of the most useful conjugated polymers, with extensive electrical, optical and chiroptical properties [71-82]. Following LC polyacetylene derivatives, many efforts have been made to synthesize LC-PT derivatives [22-27, 31-34]. Here, we describe the synthesis and properties of PT derivatives and their analogues of LC or FLC nature. 

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