Effects of Specific Additives

Cationic micellar growth in salt-free aqueous solutions of CTA2,6-dichlo-robenzoate, CTA2-chlorobenzoate, CTA3,5-dichlorobenzoate, CTA4-chloroben- 

The formation of rodlike micelles from spherical micelles of alkylpyridinium surfactants in aqueous solution is strongly dependent on the following (1) structure and hydrophobicity of counterion, (2) hydrophobicity and the type of substituent as well as the substituent pattern of the aromatic ring counteri-ons/additives, (3) the microenvironment of the counterion (substituent) in the Stem region, and (4) the structure of the surfactant monomer (i.e., the surfactant cation) where head group effects are proposed to be the main driving force for sphere-to-rodlike transition.  

Although some qualitative explanations for the formation of flexible rodlike micelles are found in the recent literature, it is not fully clear at the molecular level how such micelles are formed and why they are formed in the presence of some specific additives, whereas in the presence of other additives of the same class of compounds, such micelles do not form. 

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Impurities in the reactant, even when present in very small amounts, may participate in, and hence alter, both the rates and mechanisms of decomposition reactions. It is thus necessary to know what impurities are present, their concentrations and spatial distributions. Sometimes the effects of specific additives, introduced as solid solution (doping), may be studied to give information on the reaction mechanism. Although not always provided, a full elemental analysis of the reactant is an essential prerequisite for the study of the decomposition. There is discussion of futher aspects of reactant characterization in Chapter 6. 

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