Association phenomenon

Association Phenomena.—This section includes polymer-polymer and polymer-small molecule associations. In general, the first type leads to severe spectral broadening resulting in the loss of intensity from conventionally recorded high-resolution spectra. Thus in aqueous solutions of block copolymers of ethylene oxide with styrene and butadiene, no signals from the polyolefin are seen due to the formation of polyolefin-cored micelles. Intermolecular association has also been observed in styrene-ethylene dimethacrylate random copolymers in CCI4, and the 

Ishizuka and N. Murayama, Yamagata Daigaku Kiyo, Kogaku, 1979, 15, 167. 

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The thermodynamic study of thiazole and of some of its binary mixtures with various solvents has led to the determination of important practical data, but also to the discovery of association phenomena between thiazole and some solvents and of thiazole self-association. 

Computational fluid dynamics (CFD) is the analysis of systems involving fluid flow, energy transfer, and associated phenomena such as combustion and chemical reactions by means of computer-based simulation. CFD codes numerically solve the mass-continuity equation over a specific domain set by the user. The technique is very powerful and covers a wide range of industrial applications. Examples in the field of chemical engineering are ... 

The nature of spin state transitions in solid complexes of iron(II) and the interpretation of some associated phenomena. E. Konig, G. Ritter and S. K. Kulshreshtha, Chem. Rev., 1985, 85, 219 (91). 

Carbon dioxide 53 55). If excess C02 and polar solvents are used the carboxylation is quantitative and free of side reactions. In nonpolar solvents association phenomena favor ketone formation 55). An alternate way to get re-carboxylic polymers is to react the living sites with a cyclic anhydride 561. 

Electric double layers are formed in heterogeneous electrochemical systems at interfaces between the electrolyte solution and other condncting or nonconducting phases this implies that charges of opposite sign accumnlate at the surfaces of the adjacent phases. When an electric held is present in the solntion phase which acts along snch an interface, forces arise that produce (when this is possible) a relative motion of the phases in opposite directions. The associated phenomena historically came to be known as electrokinetic phenomena or electrokinetic processes. These terms are not very fortunate, since a similar term, electrochemical kinetics, commonly has a different meaning (see Part 11). 

Association phenomena and basicity The methods hitherto quoted are all based on the pronounced changes which can be observed on interaction of electron donors and acceptors, and which can be quantitatively analysed. 

The association phenomena occurring with alkyllithium initiators in nonpolar solvents results in very low polymerization rates. A typical styrene or isoprene polymerization by... 

Ionic ROP shows most of the characteristics described in Chap. 5. There is minimal discussion in this chapter of those characteristics that are similar to those for carbon-carbon and carbon-oxygen double-bond polymerizations. Ionic ROP shows analogous effects of solvent and counterion, propagation by different species (covalent, ion pair, free ion), and association phenomena. 

Association-phenomena In order to find out the associations of all participating species in the catalytic process (better in all product-determining elementary steps of the cycles), caused by their properties [symbol f ( )] and concentrations (symbol f [ ]), we have applied and modified the Method of Inverse Titration to organo-metallic chemistry (Chap. 3) (for a review of titration procedures see Ref.. ... 

Borchard, W., Pyrlik.M., Rehage,G. Association phenomena of PMMA in solution and gels. Makromol. Chem. 145,169-188 (1971). 

The Use of Thin Film Dialysis and High Resolution NMR to Study Conformation and Association Phenomena... 

Our approach has been essentially empirical in nature with less emphasis on the theoretical. We have isolated single substances, proved their purity, and determined their covalent structure by classical methods of organic chemistry we have then used these substances of molecular weight ranging from 1,000 to 14,000 as model solutes for the study of conformation and intermolecular interaction. Solutes of special interest have been gramicidin SA (2), bacitracin A (3), polymyxin B, and the tyrocidines A, B, and C (4). All are cyclic antibiotic polypeptides. The first three behave in aqueous solution as reasonably ideal solutes and do not associate, but the tyrocidines associate strongly and are interesting models for the study of association phenomena. Other model solutes of... 

One term that is frequently associated with nuclear chemistry is that of radiochemistry. The term radiochemistry refers to the chemical manipulation of radioactivity and associated phenomena. All radiochemists are, by definition, nuclear chemists, but not all nuclear chemists are radiochemists. Many nuclear chemists use purely nonchemical, that is, physical techniques, to study nuclear phenomena, and thus their work is not radiochemistry. 

This article discusses some micellar and liquid crystalline phases with nonionic substances, water, and hydrocarbons and some factors are delineated for their association phenomena. Lipid phase behavior has an extremely important direct influence on certain biological phenomena (Chapter 10) and is treated in Chapter 4. The treatment here is limited... 

It is clear that, in general, the less associated alkyllithiums are more reactive as initiators than the more highly associated species. The effect of solvent on initiator reactivity is also consistent with the importance of association phenomena. Aromatic solvents, which tend to decrease the average degree of association and promote dissociation processes of aggregates, are reported to lead to initiation rates which are two to three powers of ten faster than in aliphatic solvents 30,40). 

Suess, E. Interaction of organic compounds with calcium carbonate. I. Association phenomena and geochemical implications. Geochim. Cosmochim. Acta 34, 157-168 (1970). 

Further demonstrations of this sort of counterflow phenomenon for many different substrates in virtually every type of cell have been used as functional hallmarks of carrier-mediated transport. Experimental demonstration of this effect precludes transport being mediated either by simple diffusion or by fixed pores in the membrane. In reviewing 20 years of experimental work related to the carrier hypothesis, LeFevre (1975) lists a number of key functional properties of carrier mediated transport, all of which have stood the test of the subsequent 20 years. These include saturation of transport with increased substrate concentration and associated phenomena such as competition between similar substrates, high rates of unidirectional transport, and countertransport. Also covered are flux coupling (including trans effects and cotransport), chemical specificity, inhibition by protein-specific reagents, hormonal regulation, and a steep dependence of the rate of transport on temperature (included only to bemoan its common inclusion in textbooks ). 

This simple relationship follows from the equation for the state of an ideal gas. In practice, deviations are frequently observed which are attributed to dissociation or association phenomena. 

When cocaine is applied to the conjunctiva, it produces local anesthesia (which may not extend to the iris), local anemia (which extends to the iris but not to the retina), and submaximal dilatation of the pupil by peripheral sympathetic stimulation. Mydriasis occurs also on systemic administration. The accommodation is impaired, but the light reflex is preserved there is some exophthalmos. The intraocular pressure is usually lowered, but may be increased. The mydriasis and its associated phenomena are not produced by most of the cocaine substitutes. 

Ion association and other associative phenomena are not discussed. It is vital that such effects are considered, especially at higher ionic strengths, where significant association occurs. In kinetic studies, allowances for ion pairing are made by distinguishing between the stoichiometric ionic concentrations and the actual ones. 

Association phenomena increase and become much more important as the relative permittivity of the solvent decreases. Electrolytes which are completely, or nearly completely, dissociated in water are extensively associated in low relative permittivity solvents. 

Curtis, L.A. and Barse, A., Sexual anomalies in estuarine snail Ilyanassa obsoleta imposex in females and associated phenomena in males, Oecologia, 84, 371, 1990. 

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