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Salt effect on the complex formation between cationic gemini surfactant and anionic polyelectrolyte in aqueous
Xiaoyong Wang1, Jinben Wang, Yilin Wang
1Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 6, 2004
Summary
Salt concentration has minimal impact on sodium carboxymethylcellulose (NaCMC) and gemini surfactant (C12C6C12Br2) complex formation. However, adding Triton X-100 (TX100) increases the salt concentration needed for complex formation, showing a shift in interaction dynamics.
Area of Science:
- Colloid and Surface Chemistry
- Polymer Science
- Supramolecular Chemistry
Background:
- Understanding polyelectrolyte-surfactant interactions is crucial for developing advanced materials.
- Sodium carboxymethylcellulose (NaCMC) is an anionic polyelectrolyte, while hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (C12C6C12Br2) is a cationic gemini surfactant.
- The presence of nonionic surfactants like Triton X-100 (TX100) can significantly alter these interactions.
Purpose of the Study:
- To investigate the effect of salt concentration on the complex formation between NaCMC and C12C6C12Br2.
- To examine how the nonionic surfactant TX100 influences the salt effect on C12C6C12Br2/NaCMC complexation.
- To elucidate the competing mechanisms of interaction enhancement and screening in these systems.
Main Methods:
- Turbidimetric titration was employed to determine critical aggregation concentrations.
- Steady-state fluorescence measurements provided insights into micelle formation and interactions.
- Mobility measurements assessed the electrostatic properties of the complexes.
Main Results:
- The critical aggregation concentration (cac) for C12C6C12Br2/NaCMC complexes showed little dependence on sodium bromide (NaBr) concentration.
- In the presence of TX100, the critical ionic surfactant mole fraction (Yc) for complex formation increased significantly with rising NaBr concentration.
- These findings suggest a balance between interaction enhancement and electrostatic screening, with screening dominating in the presence of TX100.
Conclusions:
- The salt effect on C12C6C12Br2/NaCMC complexation is characterized by a compensation between increased interaction and electrostatic screening.
- In the C12C6C12Br2/TX100/NaCMC system, electrostatic screening becomes the dominant factor, suppressing electrostatic binding.
- This study highlights the complex interplay of salt concentration, surfactant structure, and nonionic additives in polyelectrolyte-surfactant systems.