Liquid crystalline oligomers

To facilitate processing of these copolyesters it would seem reasonable to redesign them in the form of low viscosity, branched, liquid crystalline oligomers which could be crosslinked (see Fig. 32). In fact, it was found that low melting... 

Fig. 3.9 Schematic illustration of self-organizing process for the composite of liquid crystalline oligomers and SWNTs. Reproduced with permission from [86]. Copy right The Royal Society of Chemistry 2009...

V. Percec, M. Kawasumi, P.L. Rinaldi, V.E. Litman, Synthesis and characterization of cyclic liquid crystalline oligomers based on l-(4-hydroxy-4 -biphenylyl)-2-(4-hydroxyphenyl)butane and 1,10-dibromodecane. Macromolecules 25, 3851-3861 (1992)... 

Many unconventional and discotic compounds, especially those with large molecules, show a pronounced tendency towards the glassy state [196,319f, 319g, 352-354, 358-365]. Glassy states are well known and common in polymers, and liquid crystalline oligomers show phase behaviours that are intermediate between those of low molecu-... 

Self-Reinforced Composite from Liquid Crystalline Oligomers via Reactive Extrusion Process... 

PSU) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and has a drastic effect on phase transitions exhibited by liquid crystalline oligomers. ... 

J.6 Thermotropic liquid crystalline oligomers (see also Volume 5, Chapters 38 and 39)... 

Side chain liquid crystalline oligomers were synthesized in order to obtain a more detailed understanding of the change in phase behavior in going from the monomer to the polymer. One study involved monodisperse oligo(methylsiloxane)s with mesogenic side chains (28). ... 

The final properties of conventional PU ionomers, which are controlled to a large extent by microphase separation, can be further varied by incorporation of appropriately chosen additives. In a recent study, the effect of a liquid crystalline oligomer (LCO) on the DMS and on the molecular dynamics of a PU ionomer was investigated by DRS and TSDC [63]. The final chemical structure of the PU ionomer with a concentration of ionic centers of 8% is shown in Scheme 2. Composites with the LCO cholesteric ester of caprylic acid (PU/LCO composites) were obtained by casting from a common solvent (dimethyl form-amide) LCO mass fractions w = 0, 0.02, 0.10, and 0.20. 

Boden, N., Bushby, R.J., Cammidge, A.N., Martin, P.S. Glass-forming discotic liquid-crystalline oligomers. J. Mater. Chem. 5, 1857-1860 (1995)... 

Hydrosilation reactions have been one of the earlier techniques utilized in the preparation of siloxane containing block copolymers 22,23). A major application of this method has been in the synthesis of polysiloxane-poly(alkylene oxide) block copolymers 23), which find extensive applications as emulsifiers and stabilizers, especially in the urethane foam formulations 23-43). These types of reactions are conducted between silane (Si H) terminated siloxane oligomers and olefinically terminated poly-(alkylene oxide) oligomers. Consequently the resulting system contains (Si—C) linkages between different segments. Earlier developments in the field have been reviewed 22, 23,43> Recently hydrosilation reactions have been used effectively by Ringsdorf 255) and Finkelmann 256) for the synthesis of various novel thermoplastic liquid crystalline copolymers where siloxanes have been utilized as flexible spacers. Introduction of flexible siloxanes also improved the processibility of these materials. 

Liquid crystalline main chain polymers with siloxane spacer groups were obtained by the hydrosilation of (Si—H) terminated polydimethylsiloxane oligomers and mesogenic groups with terminal double bonds as shown in Reaction Scheme XVII-(a). Reactions were usually carried out in THF with the Wacker Oil catalyst 255). Completion of the reactions was followed by the disappearance of the strong (Si—H) absorption band at 2140 cm-1 using IR spectroscopy. 

This chapter is a preliminary report of our results. We found a procedure by which PHBA can be reacted with pre-formed amorphous oligoester diols at 230°C with minimal formation of phenol, an undesirable by-product. The products of such reactions are oligomers containing amorphous and ordered phases. They appear liquid crystalline. While the oligomer structures formed in the procedure described here differ from those of the previous paper, they form baked enamel films of exceptional hardness, toughness, and adhesion. 

A direct esterification procedure by which a linear polyester diol can be modified with p-hydroxybenzoic acid (PHBA) was demonstrated. The products are oligomers in which phenolic end-groups appear to predominate. They are heterogeneous and are probably liquid-crystalline when 30 wt% or more of PHBA is incorporated. The procedure has the advantage that appears adaptable to large scale production but the disadvantages that the polyols are predominately phenolic and are contaminated with small amounts of phenol and unreacted PHBA. 

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. °... 

These hydrophobic crystallites fit properly into a planar bilayer by formation of H-bonds between the free end groups of the oligomers and the polar head groups of the phospholipids. In other words, a membrane contains islands of crystalline poly(3-HB) within the liquid crystalline phospholipid phase. A schematic representation is shown in Figure 8. Single-channel current fluctuations are assumed to... 

Fig. 15 Schematic illustration of the self-organizing processes for the composite of liquid crystalline OPV oligomers and SWCNTs [465]. (Reproduced by permission of The Royal Society of Chemistry)...

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