Mixed micelles of benzyldimethylhexadecylammonium chloride and dodecylpyridinium chloride in glycol-water mixtures

The conductance values of benzyldimethylhexadecylammonium chloride (BNDACl) -dodecylpyridinium chloride (DDPCl) mixtures over the entire mole fraction range of BNDACl (alpha(BNDACl)) were measured in aqueous binary mixtures of ethylene glycol (EG), propylene glycol (PG), butylene glycol (BG), diethyl ene glycol (DEG), diethylene glycol monomethyl ether (DEGMME), diethylene g lycol monoethyl ether (DEGMEE) and diethylene glycol monobutyl ether (DEGMB E) containing 10 and 20% w/w of each additive in their respective binary mi xtures at 30 degrees C. Each conductivity curve shows a single break over t he whole mole fraction range of BNDACl+DDPCl mixtures except in the presenc e of BG and DEGMBE, where no break was observed for BNDACl and even beyond the BNDACl-rich region of the mixtures. From the conductivity data, various micellar parameters in the absence and presence of glycol additives were c omputed. A variation in the micellar parameters showed that BNDACl+DDPCl mi xtures undergo strong structural changes in the DDPCl-rich region in compar ison with the BNDACl-rich region. The additive effect was quite systematic in both the regions. The results suggest that BNDACl monomers undergo stron g interactions with the additive molecules, whereas such interactions are c omparatively very weak in the case of DDPCl. The mixing behaviour of BNDACl +DDPCl is quite non-ideal and demonstrates the strong repulsive interaction s due to the incompatibility between the unlike bulky head groups in the DD PCl-rich region. The antagonistic behaviour is further systematically enhan ced with the increase in the hydrophobicity of the additive molecules, wher eas it is decreased in the BNDACl-rich region.