P-azoxyanisole

A typical liquid-crystal molecule, such as p-azoxyanisole, is long and rodlike (14). Their rodlike shape enables the molecules to stack together like dry, uncooked spaghetti they lie parallel to one another but are free to slide past one another along their long axes. Liquid crystals are anisotropic because of this ordering. Anisotropic materials have properties that depend on the direction of measurement. The viscosity of liquid crystals is least in the direction parallel to the long... 

Consider the structure of p-azoxyanisole (14). (a) Using the VSEPR model, draw a picture that represents the shape of the molecule and predict the CNN bond angles, (b) What features of the bonding of this molecule give rise to its rodlike nature ... 

The molecule p-azoxyanisole (14) has a liquid crystalline range of approximately 117° to 137°C. How might this molecule be modified to lower its melting point and make it more suitable for lower-temperature applications (near room temperature, for example) ... 

In 1933, Bernal and Crowfoot [1] reported on the solid state polymorphism of p-azoxyanisole. They found two crystalline modifications of this compound, a stable yellow form and an unstable white polymorph. Krigbaum et al. [31 reexamined the crystal structure of the stable yellow form. The compound shows an imbricated structure which is the basic packing required for nematic behaviour according to Gray [132]. 

Azoxyonisole or Azoxydianisole (called Azoxyanisol or Dimcthoxy-azoxybenzol in Ger), ClV0 C6H4(Na0) C6H4-0-CHa mw 258.27, N 10.85%. Three isomers are described in the literature o,o -Azoxy-atiisols (Ref l)j rn,m -Azoxyatiisois (Ref 2) and p,p -Azoxyanisole (Ref 3). The nitro derivs of Azoxyanisole may be of interest as expl ingredients... 

A typical liquid crystal molecule, such as p-azoxyanisole, is long and rodlike (14). 

Grushka, E. and Solsky, J.F., p-Azoxyanisole liquid crystal as a stationary phase for capillary column gas chromatography, Anal. Chem., 45, 1836, 1973. 

Figure 10.11 (a) Apparent viscosity for Poiseuille flow of p-azoxyanisole (PAA) as a function of the effective shear rate AQjnR y where Q is the volumetric flow rate and R is the tube radius, for homeotropic boundary conditions. (b) The data of (a) are replotted against AQjnR, which is proportional... 

One of the few exceptions are molecules like p-azoxyanisol, p-azoxyphenetol and anisaldazine, which form anisotropic liquids and for which Wolf [Physik and Chemie der Grenzjlachen. Vol. 1, Springer (1957), p. 44) reports y T) curves with kinks. 

In the nematic liquid crystalline state, groups of molecules orientate spontaneously with their long axes parallel, but they are not ordered into layers. Because the molecules have freedom of rotation about their long axis, the nematic liquid crystals are quite mobile and are readily orientated by electric or magnetic fields. Nematic liquid crystals are formed, for example, when p-azoxyanisole is heated. 

Exist over small temperature range between solid and liquid Example p-azoxyanisole... 

Like ebulliometry, the cryoscopic method is also limited to relatively low-molecular-weight polymers with up to 50,000. A newer variation of this method involves the solute-induced depression of the nematic-isotropic transition temperature for a liquid crystal solvent such as p-azoxyanisole [2]. This technique appears to be particularly convenient for high-molecular-weight polymers and may be applicable for M values as high as 10 . 

NMR investigations of mesomorphic materials were initiated by Spence, Moses, and Jain, who observed that the NMR signal from the nematic phase of p-azoxyanisole (PAA) had a line width intermediate between that of a solid and a liquid 32). In later papers 13, 31) they discuss the structure found in the NMR spectrum of this compound and the deu-terated methoxy analog, ascribing the structure to dipole-dipole interactions. In the last of these papers 13) they discuss the temperature dependence of the separation of the triplet structure in PAA. The investigation of the nematic state of PAA and higher homologs was next taken up... 

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