Sythesis And Aggregation Behavior Of Cationic Silicone Surfactants

Silicone surfactants consist of a permethylated siloxane/silane group coupled to one or more polar groups, which are a new class of surfactants with excellent surface active. They are widely used in industrial fields, such as agricultural adjuvant, polyurethane foam additives, paint additives, emulsifiers in cosmetics, and textile conditioning. This wide application is attributed to those properties of silicone surfactant:(i) its high surface activity and "super-spreading",(ii) its low toxicity and excellent association behavior and (iii) its low glass transition temperature even for higher molecular weight make it easier to use at room temperature. With the further development of silicone materials, silicone surfactants will be widely investigated and under the spotlight.In this dissertation, a series of cationic silicone surfactants with different hydrophobic groups, different hydrophilic groups and different counterion groups are designed and prepared. Their aggregation behaviors in aqueous solution have been investigated systematically in order to study the effect of hydrophobic groups, hydrophilic groups and counterion groups on aggregation behavior of cationic silicone surfactant. Our research is helpful to establish the dependence of aggregation behavior of cationic silicone surfactants on their structures. This dissertation is divided into5parts as follows:The first part, the types, synthesized methods and study progress of silicone surfactants are summaried.The second part, a series of cationic silicone surfactants with different hydrophobic groups, different hydrophilic groups and different counterion groups are designed and synthesized. The results of FT-IR,1H NMR, and ESI-MS indicate that these cationic silicone surfactants are all objective products.The third part, the surface activity and aggregation behavior of Si4mimCl, Si4pyCl and Si4ACl in aqueous solution was systematically investigated by surface tension, electrical conductivity, and steady-state fluorescence. Surface tension of water can be reduced almost to20mN·m-1with the addition of the cationic silicone surfactants. The results indicate that all the three surfactants exhibit admirable surface activity. Because of the effect of the headgroups, the critical micelle concentrations (CMC) values increase following the order Si4pyCl<Si4mimCl<Si4ACl, and Si4pyCl packs more tightly at the air/water interface compared with Si4mimCl and Si4ACl. Electrical conductivity measurements show that all the three cationic silicone surfactants have low degree of counterion binding (β) and the β values for Si4pyCl and Si4ACl increase with increasing the temperature in the investigated temperature range. Thermodynamic parameters (△Hm0,△Sm0, and△Gm0) of micellization indicate that the micellization for Si4mimCl in aqueous is enthalpy-driven, and that for both the Si4pyCl and Si+ACl is entropy-driven. The I1/I3value for Si4imimCl is larger compared with Si4pyCl which may be caused by the π-π interaction between the imidazolium and the pyrene, consequently, the pyrene molecules tend to stay near the head group region. While, intermolecular hydrogen bonds of headgroup for Si4ACl cause the pyrene to be solubilized in the palisade layer near the polar headgroups in micelles, and therefore, Si4ACl has the lowest values of I1/I3.The forth part, aggregation behavior of Si4ACl, Si3ACl and Si3C2ACl in aqueous solution was investigated by surface tension and electrical conductivity. The results show that all the three cationic silicone surfactants perform admirable surface activity. Because of the effect of the hydrophobic groups, the critical micelle concentrations (CMC) values increase following the order Si3C2ACl<Si4ACl<Si3ACl, and Si3C2ACl packs more compactly at the air/water interface compared with Si4ACl and SiaACl. Thermodynamic parameters (△Hm0,△Sm0, and△Gm0) of micellization derived from electrical conductivities indicate that the micellization for Si.C2AC and Si.ACl in aqueous solution both is enthalpy-driven, and that for the Si4ACl is entropy-driven. The heat capacities,△cm0,p, values are positive for Si4ACl, indicating that there is the attractive interaction between the nitrogen atom of one surfactant molecule and the oxygen atom of another surfactant molecule for Si4ACl. The addition of sodium halides in the aqueous solution decreases CMC remarkably, however, the surface tension at CMC keeps the same with the salt-free system.The fifth parts, the aggregation behavior of three silicone ionic liquids, Si4pyAc, Si4pyCl and Si4pyNO3, in aqueous solution was systematically investigated by surface tension, electrical conductivity, dynamic light scattering (DLS), and transmission electron microscope (TEM). Surface tension of water can be reduced almost to20mN·m-1with the addition of the silicone ionic liquids, indicating that all the three silicone ionic liquids exhibit excellent surface activity. The critical micelle concentrations (CMC) values of Si4pyNO3is less than that of Si4pyAc. Electrical conductivity measurements show that the degree of counterion binding (β) for Si4pyNO3is twice larger than that for Si4pyAc. Thermodynamic parameters (△Hm0, ASm0, and AGm0) of micellization derived from electrical conductivities indicate that the micellization for Si4pyNO3and Si4pyAc is enthalpy-driven process. The heat capacities,△cm,p0, are negative for two silicone ionic liquids (Si4pyNO3and Si4pyAc) relating to the removal of water accessible non-polar surfaces.