Chemical modification of nano silica
The chemical modification of Nano-SiO2 is mainly to use a large number of hydroxyl groups on the surface of Nano-SiO2 to react with modifiers, so as to reduce the hydroxyl number, change the hydrophilicity and hydrophobicity of the particle surface, and introduce different groups as required to expand the application scope of Nano-SiO2.
(1) Coupling agent modification method
Among the common coupling agent modification methods of nano silica, silane coupling agent is the most widely used one, which can contract with the hydroxyl group on the surface of nano silica to form silica oxygen bond.
Chemical modification of nano silica
The chemical modification of Nano-SiO2 is mainly to use a large number of hydroxyl groups on the surface of Nano-SiO2 to react with modifiers, so as to reduce the hydroxyl number, change the hydrophilicity and hydrophobicity of the particle surface, and introduce different groups as required to expand the application scope of Nano-SiO2.
(1) Coupling agent modification method
Among the common coupling agent modification methods of nano silica, silane coupling agent is the most widely used one, which can contract with the hydroxyl group on the surface of nano silica to form silica oxygen bond.
When the coupling agent is used to modify the surface of nano silica, the coupling agent needs to be hydrolyzed before it can react with nano silica. However, the hydrolysate will self condense, which hinders the reaction between the hydrolysate and the hydroxyl group on the surface of silica, to a certain extent, reduces the coupling efficiency, and makes the surface modification of nano silica incomplete.
(2) Alcohol ester modification method
Alcohol ester method is to change the wettability of silica surface by the reaction of aliphatic alcohol with hydroxyl groups on the surface of nano silica under high temperature and high pressure.
Compared with the silane coupling agent method, the alcohol ester method has the advantages of low price, easy synthesis and structure control. However, the modification effect is affected by the alkyl chain length of alcohol, and it needs to be carried out at high temperature and high pressure, which requires high reaction conditions.