Interaction of cationic gemini surfactant tetramethylene-1,4-bis(dimethyltetradecylammonium bromide) with anionic polyelectrolyte sodium carboxymethyl cellulose, with two different molar masses, in aqueous and aquo-organic (isopropanol) media

Abstract

A comparative study of the interactions of the cationic gemini surfactant tetramethylene-1,4-bis(dimethyltetradecylammonium bromide) (14-4-14) with anionic polymer sodium carboxymethylcellulose (NaCMC), with two different molar masses, was performed in water and isopropanol (IP)–water media. The interaction process was studied in detail using conductometry, tensiometry, turbidimetry and viscometry. At very low concentration, 14-4-14 monomers interact with the polymer. Above the critical aggregation concentration (cac), small micelle-like aggregates form complexes with the polymer. During the interaction process, coacervates are formed beyond C_s (polymer saturation concentration), which initially grow by aggregation and stay in the solution throughout the process. The interaction process is affected by addition of isopropanol into the medium. The intrinsic viscosities of the two NaCMCs were determined by using Huggins and Kraemer equations. Dynamic light scattering (DLS) study helps to determine the hydrodynamic size of the dispersed polymer and its surfactant-interacting complexes. The hydrodynamic size of the dispersed polymer and its interacting complex in IP–water media is lower than that obtained in aqueous solution. The surface morphology of the solvent removed polymer and its surfactant-interacting complex were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The pattern of the morphologies depends on the polymer–surfactant composition and the solvent environment.