Benzylic and pyridinium head groups controlled surfactant-polymer aggregates of mixed cationic micelles and anionic polyelectrolytes

Abstract

The oppositely charged electrostatic interactions between cationic single and mixed micelles of benzyldimethylhexadecylammonium chloride (BHDACl), hexadecylpyridinium bromide (HPyBr), hexadecylpyridinium chloride (HPyCl), and their mixtures with anionic polyelectrolytes, namely carboxymethylcellulose sodium salt (CMC) and polystyrene sulfonate sodium salt (PSS) were studied with the help of conductivity (κ), viscosity (η), turbidity (τ), and NMR studies. κ showed single aggregation process, which was represented by apparent critical micelle concentration, acmc, of each surfactant in aqueous polyelectrolyte solution. Both η and τ demonstrated strong electrostriction effects in the case of BHDACl-polyelectrolyte systems due to weak electrostatic interactions in view of steric hindrances created by benzylic group of BHDACl. 1H NMR results showed that the head group proton resonances of BHDACl upon incorporation of HPyBr or HPyCl in the presence of CMC or PSS remained identical to that in pure water, which demonstrated very weak interactions between BHDACl and polyelectrolytes. A less shielding of pyridinium head group protons by BHDACl in the presence of polyelectrolytes in comparison to that in pure water indicated favorable electrostatic interactions between pyridinium head groups and anionic polyelectrolytes. HPyBr in comparison to HPyCl showed stronger interactions with polyelectrolytes.