Synthesis, Characterization And Determination Of Surfactant Property Of Hydrolysis Resistant Disilane Surfactant In Pesticide

It can improve the property, enhance the use rate and strengthen potency of pesticidepreparation to add surfactants. Organosiloxane surfactants have excellent surface activity,much better scalability and much higher porosity permeability. They are used more and morewidely in the field of pesticide. But the hydrolyzation of the organosiloxane surfactants is easy.This is mainly beacause that Si-O-Si bond or Si-O-C bond of the skeleton of theorganosiloxane surfactant proned to reacte with proton acid, inorganic acid anhydride, alkalimetals, metal hydrides, water, alcohols and so on. There are several ways to settle the problemof hydrolysis, such as introducing the bulky substituent groups in the hydrophobic chain,extending hydrophobic chain of organosiloxane, using silane and carbosilane as hydrophobicgroup and capping polyether of hydrophilic chain.The hydrogen-containing disilane first was prepared by （CH₃）₃SiCl and （CH₃）₂HSiClbased on Wurtz coupled method using sodium as reductive coupled agent and xylene asdissolvant, which was characterized by FT-IR, UV and GC; then the disilane surfactant（DSS）was synthesized based on hydrosilation with the materials of the synthetichydrogen-containing disilane and methoxy-terminated polyether polyols using Karstedt Pt ascatalyst.In synthesis of the hydrogen-containing disilane, the effection of proportion of reactants,the concentration of reactants,15-crown-5dosage, the reaction temperature and time on yieldof hydrogen-containing disilane was studied. The optimum experiment conditions of thesynthesis were ensured: n（Na）: n（reactant materials）=1.05:1, n1（CH₃）₃SiCl: n₂（CH₃）₂HSiCl=1.2:1, the concentration of reactants1.8mol/L,15-crown-5dosage2%of the reactionmaterials, the reaction temperature and time80℃and11h respectively. And in the condition,the yeild of intermediate product could reach79.9%.In synthesis of DSS, the effection of the materials adding way, dosage of catalyst, the reaction temperature and time, proportion of reactants on yield of the DSS was studied. Thefeeding mode was ascertained that activating Si-H by Karstedt Pt catalyst at low temperatureshould be done at first, then dropping methoxy-terminated polyether polyols; The optimumexperiment conditions of the synthesis were ensured: Karstedt Pt catalyst dosage0.001%, thereaction temperature95℃and time4h, proportion of reactants was ensured: n（Si-H）: n（C=C）=1.1:1. In the condition, the yeild of product could reach98.9%. Besides, Speier Pt andKaratedt Pt catalysts were synthetized, and the synthetic Karstedt Pt was characterized by IR.Based on the catalytical performance, Karstedt Pt was selected as the catalyst in hydrosilationreaction.On the other hand, the property of DSS was determined, and results showed that itsrefractive index was1.4487and cloud point was46℃. The critical micelle concentration（CMC） was0.9g/L and the surface tension of0.1%surfactant solution was22.49mN/m. Thesurface tensions of0.1%surfactant solution under different pH values were determined, andthe stability of hydrolysis was also studied. Results showed that under pH=6.94and pH=4.12, the surface tensions of0.1%surfactant solution had a little change in30d, and itstabilized at about24.4mN/m. Therefore, the results showed the better hydrolysis stability ofthe surfactant. The diameters on different hydrophobic surfaces of the0.1%surfactantsolution were studied, and it is obviously that both DSS and trisiloxane surfactant （TSS）which has the same hydrophilic group to DSS, have a well spreadability on glass surface. Buton polystyrene board and wax paper, DSS performed a worse spreadability than TSS.