Exploration And Research On The Mechanism Of Hydrosilylation Catalyzed By Speier Platinum

Silicone functional materials have been widely used in textile,biomedical,building materials,and daily chemicals due to their excellent properties.As an important main body of silicone functional materials,organopolysiloxane has the characteristics of low surface tension,lipophilic hydrophobicity,aging resistance and weather resistance,but its weak hydrophilic properties limit the wider application of this series of materials.Therefore,by imparting hydrophilic properties to it through chemical and physical means,an amphiphilic organosilicon material with both lipophilic and hydrophilic properties can be obtained,which can significantly expand the application space of organosilicon functional materials.Conventional polyether-modified polysiloxane（PEPSO）,which grafts ethylene oxide/propylene oxide polyether molecular chains to the side chains and/or chain ends of the Si-O-Si main chain of organopolysiloxane,is an amphiphilic silicone copolymer,and the hydrophilic and lipophilic activity of polyether-modified polysiloxane is imparted and regulated by the hydrophilic polyoxyethylene segment of polyether.The hydrosilylation reaction catalyzed by Speier platinum has the advantages of strong applicability,few by-products and high conversion rate.It is a common method for the preparation of PEPSO copolymers and has been widely used in industrialization.However,there are not many reports in the literature on its catalytic mechanism and reaction mechanism.Computational chemistry can provide potential energy surfaces（PESs）of reaction paths,geometric and electronic properties of molecules,and combined with experimental findings,it has guiding significance for exploring reaction mechanisms and realizing controllable preparation of organic reactions.In this dissertation,the catalytic mechanism and reaction mechanism of the hydrosilylation reaction catalyzed by Speier platinum were studied respectively by quantum chemical computing and experimental research.The main contents are as follows:1.Based on the catalytic mechanism of CH and m CH proposed by Chalk/Harrod et al.,using the Gaussian 16 program and the DFT quantum chemical calculation method,the optimized configuration of each model molecule at the B3LYP-D3/def2-tzvp level was obtained,and the transition state is verified by imaginary frequency uniqueness and IRC method.After that,using the ORCA program,the high-precision double-hybrid functional PWPB95-D3 and the def2-QZVPP basis set were used to calculate and correct the single-point energy of each model molecule,and the thermodynamic and kinetic parameters,and their variation with temperature of each reaction path were obtained by the Ki STel P program.At the same time,by using the Multiwfn program to study the changes of the electron localization,orbital energy gap,chemical bond level and atomic valence state of the model compound in each reaction step,the reaction process was analyzed in detail.Finally,by drawing the potential energy surface and dividing the stages to find the rate-determining steps,the reaction energy barriers and fitting rate constants of the CH and m CH mechanisms at the PWPB95-D3/def2-QZVPP//B3LYP-D3/def2-tzvp level were obtained respective-ly:（35）G_CH is 28.23 kcal/mol,k _CH is 4.48×10¹²exp-[27.98×10³/RT]s^-1;（35）G_{m CH} is 42.03 kcal/mol,k_{m CH} is 1.17×10¹²exp-[41.01×10³/RT]s^-1,it shows that the former is more in line with the catalytic cycle process of the reaction.2.The PEPSO copolymer was prepared by using silicone oil intermediate and allyl polyether as reactants.The experiment was carried out using a pseudo-horizontal uniform design scheme.The reactants and products were analyzed and characterized by GPC,FT-IR and ¹H NMR.Taking the conversion rate as the only response index,the optimal reaction conditions under this experimental scheme were obtained:the temperature was 90°C,the reaction time was 4 h,and the feeding ratio was 1:1.3.Under the optimal reaction conditions,intermediates with different structural characteristics were selected to undergo a monoaddition reaction with polyether,and the relationship between the conversion rate and time was established by real-time sampling and GPC test.The influence mechanism of reactant’s molecular structure,weight and unit structure ratio on the reaction was studied.The results show that reducing the Si-H structure ratio can effectively enhance the reactivity of the intermediate and increase the reaction rate;Increasing the molecular weight of polyether and the proportion of EO in the hydrophilic structure will reduce the compatibility of the system,thereby weakening its reactivity.Based on the research foundation of the addition reaction of monopolyether,the strong reactive polyether and other polyethers are further selected to undergo double polyether addition reaction.The results show that the polyether with strong reactivity can effectively improve the reactivity of weakly reactive polyether,and the best effect is achieved when the ratio of the two is close;The molecular weight of polyether has a significant effect on the binary addition reaction.Small molecule strong reactive polyether can effectively improve the reactivity of macromolecule polyether,and its gain effect is positively related to its own activity.There is an obvious competitive relationship between small molecules and strong active polyethers;Strongly reactive polyethers with a large proportion of lipophilic structure PO can improve the reactivity of strong hydrophilic polyether;Strongly reactive polyethers with the same end capping groups can improve the reactivity of weakly reactive polyethers.