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Micellar Exchange Kinetics of Quaternary Ammonium Type Gemini Surfactants Monitored by Nuclear Magnetic Resonance
Jun Liu,You-ru Du,Shi-zhen Mao*,Mai-li Liu*
Author NameAffiliationE-mail
Jun Liu National Engineering Laboratory of Wheat & Corn Further Processing, Henan University of Technology, Zhengzhou 450000, China  
You-ru Du State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China  
Shi-zhen Mao* State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China maosz@wipm.ac.cn 
Mai-li Liu* State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China ml.liu@wipm.ac.cn 
Abstract:
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, 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.
Key words:  Gemini surfactants  Dynamic nuclear magnetic resonance  Molecular exchange  Exchange rate constant  Apparent activation energy  Two-step exchange mechanism
FundProject:This work was supported by the National Natural Science Foundation of China (No.21375145).
NMR方法监测季铵型双子表面活性剂的胶束交换动力学
刘君,杜有如,毛诗珍*,刘买利*
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DOI:10.1063/1674-0068/31/cjcp1708167
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