Crystalline state chemical structure effect

We have indicated that a finite value of An may provide a means of detecting orientation but its magnitude and sign may vary considerably from system to system and will depend on the chemical nature and material composition (amorphous v. crystalline). The chemical structure determines whether the refractive index (polarisability) is higher along the chain (polyethylene) or perpendici lar to the chain (polystyrene-rubbery state). The composition in turn is of importance because the intrinsic optical character of a crystal may difier from that of an amorphous chain. Furthermore, polarisability interactions known as internal field and form effects may also influence the observations and hence must be considered in many instances. 

Before proceeding, it is important to note the additional requirements that must be met by chemicals defined as chromophores on the basis of their structure. To be effective, it is also necessary that they be in the liquid crystalline state of matter. And for maximum effectiveness, they must be associated with a suitable structure that can provide a de-excitation path. This is particularly important in the case of the carboxyl-ion system. Oxygen exhibits a unique... 

We are cognizant that the structural data on hydrogen bonds derived from crystal structure analyses refer particularly to the hydrogen bond in the solid state. These data are subject to crystal field effects caused by other intermolecular forces. Just as with any discussion of covalent or ionic bonds observed in crystals, these crystal field effects have to be taken into consideration when extrapolating from the precise data available from the crystalline state to the imprecise data that applies to the liquid state in which most chemical and biochemical reactions take place. 

The recommended heat capacity data are currently being analyzed in terms of chemical structure, structure of the polymers in the glassy, crystalline and molten states. The data are further being analyzed to study the effect of branching, molecular weight and tacticity on the heat capacity of polymers. Comprehensive tabulation of heat capacities of various structural units are being prepared and will be available in the near future. 

With the exception of cellulose and chitin, plant polysaccharides are usually hydrated. Hydration often occurs in the crystalline regions as well as in the amorphous areas. When water of hydration is found in the crystallites, it may or may not affect the conformation of the polysaccharide backbone and in most cases, it affects the unit-cell dimensions, while in a few cases, the water appears to have no effect on unit-cell dimensions. The structures of six hydrated neutral polysaccharides will be examined with regards to the state of water of hydration in the structure. It wi 11 be seen that water may occur as columns or as sheets in these structures. The structures that will be discussed are (1 4)-3-p-xylan, nigeran, amylose, galactomannan, (1 3)-3-p-gTucan and (1 3)-s-P-xy1 an. The chemical structures of these polysaccharides are shown in Figure 1. 

The presence of mineral reinforcements such as talc or mica, as foreign solid particles embedded into a polypropylene matrix, usually induces a nucleation effect. A signihcant increase in the crystalline content of the polymer is evidenced if compared with the neat polymer when processed at the same setup conditions that are necessary to ensure a good accommodation of the solid particles into the amorphous phase of the polymer in order to obtain a material with a good mechanical performance (27). The comparison between PP/mica and PP/talc composites in terms of their mechanical behavior under dynamic conditions in the solid state agrees with the morphological features derived from their chemical structures of both minerals (28). 

A general statement that should be kept in mind before the individual additives are described is as follows Common to all additives is the fact that their effects depend on their solubility in the specific polymer [29, 30, 33]. The relative parameters are their chemical structure, the temperature, and the crystallinity of the matrix. Additives can only be dissolved, for instance, in the amorphous phase of semicrystalline thermoplastics, in which the additive concentration is increased during cooling from the molten state [33]. This is advantageous in terms of stabilization, since oxygen and solvent atoms are only capable of permeation through the increased lattice vacancies of the amorphous phase with its many defects. 

THE EFFECT OF THE CHEMICAL STRUCTURE ON THE STABILITY OF LIQUID CRYSTALLINE STATE... 

At first,we studied the effect of the chemical structure of polymer chain on the stability of liquid crystalline state.The liquid crystalline state of polyether-esters derived from substituted hydroquinone and substituted 1,2-bis(phenoxy) ethane-4,4 -dicarboxylic acid could be controled by the... 

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