Combined Effects of Polymer/Surfactant Mixtures on Some Physicochemical Properties Using Box-Behnken Design

Interaction of an anionic polymer sodium carboxymethyl cellulose (NaCMC) with the cationic biodegradable gemini surfactant, ethane-1, 2-diyl bis (N, N-dimethyl-N-hexadecyl ammonium acetoxy) dichloride, (16-E2-16) and the corresponding simple monomeric counterpart cetyltrimethyl ammonium chloride (CTAC) has been investigated at different temperatures by conductivity and rheology measurements. Stronger interaction of polymer with the gemini as compared to the conventional surfactant is indicated by the values of parameters such as critical aggregation concentration, critical micelle concentration, and eta (viscosity). A preliminary experimental study was performed to evaluate the effect of the mixture compositions on the surface behavior of the mixed polymer/surfactant systems under different conditions. An experimental design using response surface methodology was applied to assess factors interactions and empirical models regarding the response variables such as conductivity and viscosity. The main effects of the three independent factors: surfactant concentration, polymer concentration and temperature, were determined using the Box-Behnken design. Analysis of variance indicated that the proposed quadratic models for conductivity/viscosity of CTAC with NaCMC and 16-E2-16 with NaCMC systems successfully interpreted the experimental data with high coefficients of R-2 values, thus ensuring a satisfactory adjustment of the second-order regression model with the experimental data. Further, a low p value of < 0.0001 indicated the statistical significance of both the models. Finally, both contour and surface plots show the relative effects of the independent variables on conductivity and viscosity.