Industrial & Engineering Chemistry Research, Vol.51, No.3, 1227-1235, 2012
Interaction between Nonionic Polymer Hydroxypropyl Methyl Cellulose (HPMC) and Cationic Gemini/Conventional Surfactants
The purpose of this study was to investigate the interaction between a nonionic polymer, (hydroxypropyl)methyl cellulose (HPMC), and cationic gemini surfactants, bis(hexadecyldimethylammonium)hexane dibromide (16-6-16), bis(hexadecyldimethylammonium)pentane dibromide (16-5-16), and their corresponding monomeric counterpart cetyltrimethylammonium bromide (CTAB), by using electrical conductometry, fluorescence, and viscometry methods. It was found that the gemini surfactants interact strongly with HPMC as compared to conventional surfactant CTAB. The free energies of aggregation, Delta G(agg), micellization, Delta G(mic), and transfer, Delta G(t), associated with the binding interaction between surfactant and polymer, have also been evaluated. The negative values of Delta G(t) confirm the feasibility of interaction between the surfactant and polymer. The aggregation number (N-agg) obtained from steady state fluorescence measurement with CTAB was found to be more than with the geminis. A significant viscosity increment was observed in the case of gemini surfactants as compared to CTAB. The rapid increase of the viscosity with surfactant concentration was, therefore, attributed to the considerable cross-links among micelles and polymers (transient network).