Research On The Effect Of Spacer On The Solution Behavior Of The Amphoteric Gemini Surfactant

The research on the structure-properties of surfactant is an active area and focus for surfactant.Novel kind of surfactants,which may own good interfacial properties and low additive amounts,also with better salt tolerances and biodegradabilities,have become the current development direction for fine chemical industry.In this paper,depending on the characteristics of the amphoteric betaine surfactant structure and the gemini surfactant structure,novel gemini betaine surfactants with different spacer length were being designed and synthesized,their structure-activity relationship were investigated and elucidated,the main results were as follows:Dodecylamine?1,2-dibromoethane?1,4-dibromobutane?1,6-dibromohexane and sodium bromoethylsulfonate?Bromoethane were being used as raw materials,three kinds of novel gemini betaine surfactants were being designed and synthesized.The structure of the intermediates and final products were being characterized and confirmed by FT-IR methods.The surface properties of novel gemini betaine surfactants solutions were determined by drop volume methods,the results show that the synthesized surfactants have superior surface activities.The ?cmc of the GSB12-N surfactant increased firstly and then decreased,with the increase of the length of the spacer group.The minimum value of ?cmc can be 30.90mN/m when the value of n of spacer [-(CH2)n-] was 6.This was due to the fact that when the length of the spacer reaches a certain value,it can exhibit flexibility so that two single chains in the Gemini surfactant molecule were close to each other,thereby improving the surface properties.The temperature resistance and salt resistance were also studied.It was found that the surface active agent had good temperature resistance and salt resistance,and the order of resistance to counter ions was Na+> Ca2+> Mg2+.The aggregation behaviors of the novel Gemini surfactants were studied by molecular dynamics simulation.ATB and GAMESS(US)were used to optimize the structure of the surfactants.All molecular dynamics calculations were performed by Gromacs.The results show that the SCD value of the T=318K was larger than other SCD values.The SCD value increases with the increase of temperature,it showed that the hydrophobic tail chains tend to be perpendicular to the interface,and the molecular arrange more inseparable,The conformation of the hydrophobic tails of the surfactant molecules will change with the change of temperature.The temperature resistance of GSB12-N series surfactants was discussed at the microscopic level.The thickness of the electrical double layer of the surfactant firstly decreased and then increased as the increase of the NaCl concentration.At the same time,SCD values also demonstrated the same orderliness,Macroscopically,the surface activity firstly increased and then decreased,Consistent with the experimental rules.The mechanism of the interaction between surfactants and inorganic salts was described.