Synthesis And Properties Of Cationic Silicone Surfactants

Silicone surfactants are composed of hydrophobic silicon groups that are attached to one or more polar groups,which are one kind of novel efficient surfactants with superior surface activity.They have wide industrial applications,such as in textile and polyurethane foam manufacturing.Silicon surfactants are also used as agricultural adjuvants,cosmetics emulsifiers,wetting agents,and paint additives.Compared with hydrocarbon surfactants,silicone surfactants exhibit lower surface tension and lower toxicity,which are mainly attributed to the low cohesive energy,good flexibility,and low glass transition temperature of the siloxane chains.The study of the effect of molecular structures and the external factors on the aggregation behavior of cationic silicone surfactant has important practical and theoretical significance to the design and synthesis of novel silicone surfactants and the expansion of its application in various fields.There are four parts in this work as follows:The first part is the summary of the classification characteristics,synthesis and properties of silicone surfactants.The second part is the synthesis and characterization of organic silicone monomers and cationic silicone surfactants?Si₄pyrCl,Si₄pipCl,Si₃pipCl and EtSi₃pipCl?.The third part is the study on aggregation behavior and surface activity of Si₄pyrCl and Si₄pipCl in aqueous solution.It was investigated through analyses of electrical conductivity,surface tension,dynamic light scattering?DLS?,and transmission electron microscopy?TEM?.The effect of organic salts?sodium salicylate,sodium benzoate,sodium citrate,sodium oxalate and sodium acetate?and inorganic salts?NaI,NaBr,Na₂SO₄ and NaCl?on the aggregation behavior of cationic silicone surfactants in aqueous solution was also investigated.The aggregation was promoted by the addition of organic salts and inorganic salts,and the ability is in the order of sodium salicylate>sodium benzoate>sodium citrate>sodium oxalate>sodium acetate,and NaI>NaBr>Na₂SO₄>NaCl.In a certain organic salt,the ability to promote the aggregation increase with the increasing concentration of organic salt.Thermodynamic parameters obtained from electrical-conductivity measurements indicated that the aggregation of Si₄pyrCl and Si₄pipCl was entropy driven.Spherical aggregates with different diameters were observed by TEM.The primary study of metal extraction on Si₄pyrCl and Si₄pipCl showed that they had good extraction ability and selectivity for Au???and Pd???,which have certain significance for the separation and purification process of noble metals and for extending the application of Si₄pyrCl and Si₄pipCl.The fourth part is the study on aggregation behavior and surface activity of Si₃pipCl,EtSi₃pipCl and Si₄pipCl in aqueous.It was found that the stronger the hydrophobic groups of hydrophobic,the stronger of its surface activity,and the CMC values of these cationic silicone surfactants are in the order of EtSi₃pipCl<Si₄pipCl<Si₃pipCl.Thermodynamic parameters obtained from electrical-conductivity measurements indicated that the aggregation of Si₃pipCl and Si₄pipCl was entropy driven,and the ?G_m⁰ values of Si₄pipCl were smaller than that of Si₃pipCl.Their aggregation was promoted by the addition of inorganic salts,and the ability is in the order of Nal>NaBr>NaCl.