Micellar Exchange Kinetics of Quaternary Ammonium Type Gemini Surfactants Monitored by Nuclear Magnetic Resonance
| Autor: | Jun Liu, Shizhen Mao, Maili Liu, You-Ru Du |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Arrhenius equation
02 engineering and technology Activation energy 010402 general chemistry 021001 nanoscience & nanotechnology Kinetic energy 01 natural sciences Micelle 0104 chemical sciences chemistry.chemical_compound symbols.namesake Monomer chemistry symbols Molecule Physical chemistry Ammonium Orders of magnitude (data) Physical and Theoretical Chemistry 0210 nano-technology |
| Zdroj: | Chinese Journal of Chemical Physics. 31:159-164 |
| ISSN: | 2327-2244 1674-0068 |
| Popis: | The dynamic NMR (DNMR) method was used to detect kinetic parameters of the molecular exchange process between monomers in bulk solution and those in the micelle for Gemini surfactants, 12-s-12 and 14-s-14 (s=2, 3 and 4). The escape rate constant, k−, was derived based on the simplified equations of DNMR theory, and the apparent activation energy of escape, Ea−, was obtained based on the Arrhenius equation through temperature variation experiments. Results show that the orders of magnitude of k− for 14-s-14 and 12-s-12 are respectively 10 and 103 s−1, Ea− of 14-s-14 and 12-s-12 are respectively 54.04–73.64 and 33.42–47.09 kJ/mol. Furthermore, k− increases and Ea− decreases with the spacer length growing. In combination with the micro-polarity measurements, it was revealed that molecules of 14-s-14 and 12-s-12 have to experience conformation changes when escaping from the micelles. The two-step molecular exchange mechanism for Gemini surfactants was therefore supported. |
| Databáze: | OpenAIRE |
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