Aggregates of cationic surfactants and anionic polyelectrolytes influenced by bulky head group modifications

The conductivity (kappa), viscosity (eta), turbidity (tau), and H-1 NMR measurements of benzylhexadecyldimethyl ammonium chloride (BHDACl)+hexadecylpyridinium bromide (HPyBr) and BHDACI+hexadecylpyridinium chloride (HPyCl) mixtures in aqueous dextran sulfate (DX) and polyacrylic acid (PAA) sodium salts have been carried out. kappa, eta, and tau showed that HPyBr interacts more strongly with anionic polyelectrolytes and that too with PAA. H-1 NNIR measurements indicated that intercalation of pyridinium head group of HPyBr and HPyCl in BHDACl micelles produced deshielding to all head group protons of BHDACl, whereas vice versa produced shielding to those of pyridinium head groups. The magnitude of shielding was much stronger on HPyBr rather than HPyCl head group protons. In the presence of polyelectrolytes, the shielding of pyridinium head group by the incorporation of benzylic ones reduced in comparison to that in pure water. The results suggested that pyridinium head group interacted more strongly with DX and PAA rather than with benzylic and which had been attributed to the steric hindrances created by the latter in the course of cationic micelle-anionic polyelectrolyte interactions. (C) 2003 Elsevier B.V. All rights reserved.