Solvent-Free Synthesis And Properties Of A Series Of Novel Cationic Trisiloxane Surfactant

Trisiloxane surfactants are of current interests in various fields because of their outstanding surface/interfacial activities and wettabilities. So far, most of the investigations about trisiloxane surfactants still focus on the non-ionic molecular structure, while the surfactant with a novel cationic structure has yet been reported. In this work, four kinds of novel cationic trisiloxane surfactants have been synthesized by a solvent-free method, and the basic characteristics and application properties have been studied. The main results are listed as follows:(1) The intermediate of (Me3SiO)2Si(Me)(OC2H4)N(CH3)2was synthesized by the solvent-free method, using N,N-Dimethylethanolamine (DMEA) and Heptamethyltrisiloxane (MDHM) as materials. Then, four novel cationic trisiloxane surfactants (Me3SiO)2Si(Me)(OC2H4) N+(CH3)2RX-[R=C2H5, C3H5, C12H25, C16H33; X=Cl,Br](abbreviated as S1, S2, S3, and S4respectively) were prepared using the intermediate and different alkylating reagents (bromoethane, chloropropene, bromododecane, bromohexadecane). The structures of the intermediate and the surfactants were determined by using mass spectrum and1HNMR.(2) The synthesis of (Me3SiO)2Si(Me)(OC2H4)N(CH3)2was optimized by using orthogonal analysis method. The sequence of the reaction factors that effect the conversion of MDHM is catalyst quantity> temperature> mole fraction> time. The optimum reaction condition is A3B3C3D3, including that25 min for reaction time,100?temperature,1.5:1mole ratio for MDHM and DMEA, and8ppm for catalyst fraction. The conversion percentage of MDHM could be up to75.6%, and the purity of the product could be some where above98%after distillation under reduced pressure.(3) The reaction process of (Me3SiO)2Si(Me)(OC2H4)N(CH3)2was monitored by using online situ FTIR, and the conversions of the reactions were determined. The results showed that the chloroplatinic acid could catalyst the reaction efficiently, and resulted in very few by-products. Meanwhile, the dynamics of the dehydrogenation condensation reaction between MDHM and DMEA were investigated by using the integral approximation method. The results showed that the activation energy Ea=82.16kJ/mol, and reaction degree is2.(4)(Me3SiO)2Si(Me)(OC2H4) N+(CH3)2RXTR=C2H5, C3H5, C12H25, C16H33; X=Cl,Br] were prepared by using the free-solvent method. The optimum reaction conditions were obtained as?S1:the temperature of55?, the time of5h, the mole ratio of1.2for bromoethane against trisiloxane tertiary amine, and the conversion percentage could be up to99.6%;?S2:the temperature of60?, the time of5h, the mole ratio of1.4for chloropropene against trisiloxane tertiary amine, and the conversion percentage could be up to90.0%;?S3:the temperature of100?, the time of4h, the mole ratio of1.1for bromododecane against trisiloxane tertiary amine, and the conversion percentage could be up to94.0%;?S4:the temperature of105?, the time of4h, the mole ratio of1.1for bromohexadecane against trisiloxane tertiary amine, and the conversion percentage could be up to92.6%.(5) The application properties of S1, S2, S3, and S4were studied, and the results showed that the surface tension are20.7mN·m-1(S1),8.4mN·m-1(S2),22.8mN·m-1(S3)and23.8mN·m-1(S4)respectively. The CMC are5.00×10-4mol/L(S1),7.50×10-4mol/L(S2),5.00×10-5mol/L(S3) and1.00×10-4mol/L(S4)respectively. The adsorb capability shows the tight arrangement of the molecules on the water/air surface. The micelles in the bulk phase are formed simultaneously, and the adsorption is more preferential compared with the formation of micelles. The experiment of interfacial tension showed that the interfacial activities of the surfactants are excellent. The surfactants show low foaming characteristics, which would avoid the disturbing of foam in the application. The results also show that the emulsibilities of the surfactants with longer chains are better than that with shorter chains, and the emulsibilities of the surfactants with long chains (S3and S4) are stronger than that of the products sold in the market. They have excellent effect for the spreading properties of cationic trisiloxane in the paraffin.1%cation trisiloxane S3solution can reduce the contact angle to37.1°. Antibacterial experiment showed that the antimicrobial rate can reach99.99%by using75mg/L S4.