Preparation of polymethylsilsesquioxane
Polymethylsilsesquioxane is a polymer microsphere with both organic and inorganic properties. It has the characteristics of high wear resistance, high hardness, high melting point, etc. It also has the advantages of lubrication, non-toxicity, odorlessness, and transparency. It is used in rubber plastics, cosmetics, coatings, pigments, and optical products. It is currently a kind of organic silicon light diffuser that has been studied more in China and has a very broad prospect.
Preparation method
1. Preparation of polymethylsilsesquioxane by one-step sol method
The one-step sol method is that alkoxysilane monomers directly complete the hydrolysis and polycondensation reaction under alkaline catalyst conditions, that is, hydrolysis and polycondensation are carried out simultaneously at the interface of the two phases. Methyltrimethoxysilane is used as the main raw material, and is uniformly mixed with an alkaline solution with a pH value of 12 in a certain proportion, stirred at a rate of 200r/min at 25°C, and a seed solution is obtained after the reaction for 30 minutes; then methyltrimethoxysilane is added to the seed solution, and the stirring is continued for 10 minutes and then allowed to stand. After 2 hours, the solution is filtered, and the filtered solid is washed with ethanol, dried, and crushed to obtain the final product. The advantage of this method is that the use of a pre-prepared organic silicon light diffusion seed solution can effectively inhibit the abnormal expansion of microspheres, and the prepared organic silicon light diffuser has good sphericity and a narrow particle size distribution.
2. Preparation of polymethylsilsesquioxane by sol-gel method
The sol-gel method is that the monomer and water are hydrolyzed under certain conditions (or under the catalysis of acid) to form a homogeneous system, and then further undergo a polycondensation reaction under the catalysis of an alkali to form polymer microspheres with a certain cross-linked structure, in which the hydrolysis and polycondensation are carried out step by step. The hydrolysis-polycondensation two-step method uses methyltrimethoxysilane as the raw material, uses acetic acid as a catalyst for hydrolysis in an aqueous solution, and then uses ammonium hydroxide as a catalyst for condensation, and finally obtains spherical polymethylsilsesquioxane particles with diameters of 2μm, 5μm, and 10μm, respectively.
3. Preparation of polymethylsilsesquioxane by emulsion polymerization
Emulsion polymerization is a polymerization reaction in which the monomer is dispersed into an emulsion state in water under the action of an emulsifier and mechanical stirring. Methyltrimethoxysilane is added to a mixture of octane, sorbitol anhydride and water to react, and polymethylsilsesquioxane is synthesized in a water-in-oil (W/O) system by emulsion polymerization at room temperature. This method does not require heating and the use of acid or base catalysis, and the particle size distribution of the final product can be changed by adjusting the reaction time and the ratio of the amount of reactants. The particle size can be controlled at 1 to 80um.
4. Preparation of polymethylsilsesquioxane by addition method
Polymethylsilsesquioxane was prepared by the hydrosilylation method. The preparation method is as follows: vinyl-platinum complex, high hydrogen siloxane and silane with carbon-carbon double bonds were mixed with an emulsifier, emulsified, reacted at 50°C for 2h, ammonia was added to make the solution alkaline, and then the temperature was raised to 70°C and the reaction was continued for 0.5h, and finally silicone microspheres with a particle size of about 600nm were obtained.
