Abstract
Results are presented on the first extensive study on the influence of additives on the growth of gemini; alkanediyl α, ω - bis(dimethylcetylammonium bromide) surfactant micelles (16-s-16, with s = 5, 6); as measured by dynamic light scattering technique at 30°C. The effect of adding n-butanol, n-pentanol, n-hexanol, and n-hexylamine in the absence or presence of general ionic salt potassium bromide on 0.03 M gemini solutions were observed. The tendency for micelles to grow from spherical to rodlike structures is decisively influenced by the spacer length s. At 30°C, the micellar growth was more for s being 5, which has been interpreted in terms of short spacer having strong propensity for micellar growth. Addition of KBr plays a role in screening of the electrostatic interactions, thus promoting a change of morphology of the aggregates and giving rise to high hydrodynamic diameter (D h ) values. The micellar growth in presence of alcohols is interpreted in terms of the formation of the gemini–alcohol mixed micelles which followed the pattern C6OH>C5OH>C4OH. For equal chain length additives C6OH and C6NH2, the growth was more pronounced in case of alcohol. Also, in case of C6NH2, the value of D h reached to almost constancy or decreased to some extent, which is discussed in terms of its partitioning in aqueous phase. A combined presence of KBr and n-alcohols or n-hexylamine produced favorable conditions for micellar growth due to synergistic effect.
Acknowledgments
Financial support by Council of Science and Technology, U.P. (project No. CST/SERC/D-1122) is gratefully acknowledged by U.S.S. Authors are also thankful to Dr. P. S. Goyal, former Centre Director, UGC-DAE-CSR, Mumbai Centre, for his kind permission to carry out DLS experiments.
Notes
a no added salt.
b [gemini] = 0.03 M.