Institute for Color Science and Technology (ICST) Progress in Color, Colorants and Coatings 2008-2134 4 2 2011 12 12 Aggregation of an anionic azo dye with conventional cationic surfactants in premicellar region: A conductometric study 121 128 75786 10.30509/pccc.2011.75786 EN S. Javadian Farzaneh Department of Physical Chemistry, Tarbiat Modares University F. Hooshmand Department of Physical Chemistry, Payame Noor University, Urmiah Branch A. Asadzadeh Shahir Department of Physical Chemistry, Tarbiat Modares University Journal Article 2011 08 29 The interaction of Congo Red CR with a series of Alkyltrimethylamoniumbromide CnTAB, N-hexadecylpyridinium bromide CPB and N-hexadecylpyridinium CPC were investigated using conductometry technique. It was observed that the formation of dye-surfactant ion pairs takes place at surfactant concentration far below the critical micelle concentration of the individual surfactants. Aggregation was reflected by the appearance of a break point at conductometry plots. The equilibrium constant and other thermodynamic parameters for the ion pair formation were calculated on the basis of a theoretical model using the data obtained by conductometry. The reaction between dye and surfactants was revealed to be an enthalpy-driven reaction which is highly dependent on temperature and the structures of both dye and surfactant. https://pccc.icrc.ac.ir/article_75786_a57bfd698091ab7076d1da5517ee53dc.pdf