Physicochemical behaviour of the sodium salt of carboxymethylcellulose in dye, salt and surfactant environments

The interactions of the polyelectrolyte carboxymethylcellulose (sodium salt) with salts, dyes and surfactants have been studied by viscometry, conductometry, spectrophotometry and membrane potential measurements. The compact conformation of the polyelectrolyte has been realized in all the environments. The average radius of gyration, s̄, and the intrinsic viscosity, [η], decline with increasing concentration of the additives. This and the narrow pseudoternary single‐phase zones for both the carboxymethylcellulose (sodium salt)/CTAB (cetyltrimethylammonium bromide) Systematic name: hexadecyltrimethylamounium bromide. / Triton X‐100 (α‐alkylphenyl‐ω‐hydroxypoly(oxyethylene))/water and the carboxymethylcellulose (sodium salt)/CTAB/Tween 20 (poly(oxyethylene)sorbitan monolaurate)/water system suggest instability of the polymer in presence of the additives. The spectral results indicate dye aggregation (stacking) on the flexible polymer chain. The binding of CTAB with the polyelectrolyte is Langmuirian in absence of KCl and strongly co‐operative in its presence. Thermodynamic parameters have been evaluated in the light of both Langmuir and Scatchard equations. Considering water and polymer to be in separate phases, the free energy of transfer of CTAB from the aqueous to the polymer phase has been calculated.