Single-end hydrogen-containing silicone oil is a type of linear polydimethylsiloxane with a reactive Si-H bond at one end of the molecular chain and an inert methyl group at the other end. As a functional organosilicon intermediate, its unique molecular structure endows it with excellent reactivity and structural controllability. Different from similar products with hydrogen groups at both ends or side chains, it has irreplaceable advantages in precise modification, directional grafting and other scenarios, and is a core raw material for the synthesis of high-end organosilicon materials.
In terms of structural essence, the core value of single-end hydrogen-containing silicone oil stems from the high reactivity of the terminal Si-H bond and the inherent properties of the polysiloxane main chain. Under the action of a platinum catalyst, the Si-H bond can undergo an addition reaction with compounds containing unsaturated bonds (such as double bonds and triple bonds) to achieve directional graft modification, without affecting the flexibility, high and low temperature resistance and hydrophobicity of the molecular chain. Its molecular weight can be adjusted between 500-10000 through processes to adapt to different application needs. Low-viscosity products have good fluidity, high-viscosity products have excellent film-forming properties, and they have strong chemical stability, acid and alkali resistance, aging resistance, and can maintain stable performance in a wide temperature range of -50℃ to 200℃.
The current mainstream preparation process is mainly ring-opening copolymerization, using octamethylcyclotetrasiloxane (D4) as the basic monomer, methylhydrogendichlorosilane as the end-capping agent, undergoing ring-opening and end-capping reactions under the action of a catalyst, and obtaining the finished product through hydrolysis, neutralization, removal of low-boiling substances and filtration refining. The traditional process has two pain points: first, the end-capping efficiency is low, which is prone to produce by-products with hydrogen groups at both ends or uncapped, resulting in insufficient product purity; second, the molecular weight distribution is wide, which affects the consistency of reactivity and limits the application in high-end scenarios.
With the iteration of process technology, a number of optimization schemes have been implemented and achieved results. By precisely controlling the monomer ratio and reaction temperature, and accurately matching the dosage of end-capping agent with the reaction rate, the end-capping efficiency can be increased to more than 98%, greatly reducing the content of by-products. Using new platinum complex catalysts instead of traditional chloroplatinic acid not only reduces the amount of catalyst and cost, but also inhibits the occurrence of side reactions, narrows the molecular weight distribution, and improves the uniformity of product performance. At the same time, the application of solvent-free continuous production process reduces the emission of volatile organic compounds, conforms to the requirements of green chemical industry, and promotes the upgrading of single-end hydrogen-containing silicone oil from general-purpose to high-end customized type, adapting to the needs of harsh scenarios such as fine modification and biomedicine.