Study On The Synthesis, The Properties And The Thermal Degradation Kinetics Of The Acetoxyethylpolysiloxane

In spite of possessing a variety of unique and superior properties, carbofunctionalized polysiloxanes play important roles in modifitions of organic polymers,such as the copolymerization of polysiloxanes and organic polymers,with the aid of the reaction activity of the carbofunctional groups,to endow the organic polymers with the excellent properties of the polysiloxanes.This kinds of polymer is rapid developmet in silicone chemistry,and an active research field.However,because of the decomposition or rearrangement under certain conditions,their applications are limited to some extent.Understanding their rearrangement conditions and mechanisms will be of great important values for the control and application of these compounds.In this thesis,carbofunctionalized silicane monomer was synthesized with hydrosilation reaction.Acetoxyethylcyclicsiloxane,octamethylcycotetrasiloxane(D₄),hexamethyldisiloxane(MM)were used as comonomers to anionic ring-opening copolymetize under base catalysts in this experiment.Studies on molar ratio of monomers,catalysts and polymerization temperature were our main focuses.We obtained a more reasonable experimental conditions:no solvent,the mol ratio of unsaturated compound and the Si-H is 1.2:1,the optimal reaction temperature was 60-65℃for 12h,anhydrous and anaerobic system state in the hydrosilation reaction.The optimal polymerized experiment condition is as the following:Me₄NOH siloxanolate is the catalyst,the optimal reaction temperature 80-85℃,fractinal step method.We synthesized a series of carbofunctionalized polysiloxanes,and their molecular structure were characterized by FT-IR,¹HNMR etc.We also use the TGA to investigate thermal properties of the polymer.Effect of molecular weight,and cotent of functional group on the polymer was also explored.We also analysized thermal degradation activation energy,reaction order,reaction rate constant under the different temperature range by the corrected Freeman-Carrol methods.Quantum chemistry method was used to calculate the thermal degradation mechanisms of H₃SiCH₂CH₂OOCCH₃ and got the real degradation mechanism.There are two kinds of reactions in this system,and both of them are noncompetitive.The carbofunctional group introducted in the polysiloxane chain has aroused great attention.Chemical modified is always a challenge.There are much theoretical value and application prospects in searching for new cross-linking method and developing special performance polysiloxane. Now,people are interested in application of the silica ester,especially in the application of the environment and biomedicine.Polysilica-ester can be used as the water resistance in the textile industry,the protection reagents of the ionic polymerization,application of the photography and viscosity-reduced reagents.Therefore,studied on the thermal degradation mechaniam of acetoxyethylpolysiloxane,can contribute to the deeper study of its performance,and expand the scope of its application.