Synthesis and properties of biodegradable cationic gemini surfactants with diester and flexible spacers

摘要

Abstract A series of cationic gemini surfactants with diester and flexible spacers, namely C 12 -PG-C 12 , C 14 -PG-C 14 and C 16 -PG-C 16 , were synthesized, purified and characterized. The surface properties and aggregation behavior of the gemini surfactants were investigated by surface tension, electrical conductivity, fluorescence and Krafft point. These gemini surfactants possess higher surface activity than the traditional monomeric surfactants. The thermodynamic parameters exhibited that the micellization was a spontaneous and exothermic process in environment. The micellization process became less favorable with the decrease of alkyl chain length and the increase of temperature. Steady-state fluorescence measurements revealed that the micropolarity and aggregation number of micelles decreased with the increase of hydrocarbon chain length. The Krafft points were taken as 0°C, which indicated the synthesized gemini surfactants had good water solubility. The biodegradability of the gemini surfactants were evaluated in river water using Closed Bottle tested and showed their high biodegradation ratio in the open environment due to the diester bond inserting in the flexible spacer of surfactant molecules. Highlights ? The gemini surfactants with diester and flexible spacers were designed and synthesized. ? The surface properties and aggregation behavior of surfactants were investigated. ? They have higher surface activity than the traditional monomeric surfactants. ? The micellization is a spontaneous and exothermic process in environment. ? They possess good water solubility and can be classified as readily b