Polymer nanocomposite is a new kind of composite material composed of various nano-units and organic polymer materials. Metals, ceramics, clay and so on are usually used as nano additive materials. The core idea of various preparation methods of polymer nanocomposites is to effectively control the geometric parameters, spatial distribution parameters and volume fraction of the nano structural units to ensure that at least one dimension of a component phase in the system is within the nanometer scale.
Classical strategies for preparation of polymer nanomaterials
Sol-Gel complex method
It is mainly used for preparing inorganic-organic polymer nanocomposites. The preparation process is as follows:
The types of inorganic-organic nanocomposites prepared by this method are as follows:
Embedding soluble polymers directly into the inorganic network: The polymer is required to have good solubility in the cosolvent and good compatibility with the inorganic components.
The embedded polymer is covalently bonded to the inorganic network: The mechanical properties of the composite can be increased by introducing groups such as (RO)3Si, which can form covalently bonded to the inorganic components, into the polymer side group or the end of the main chain.
Organic-inorganic interpenetrating network structure: The composites prepared by this method have a three-dimensional cross-linked structure. It can effectively reduce gel shrinkage and the products have good uniformity and small size of microregion.
Many inorganic compounds have typical layered structures, and organic matter can be embedded between layers, such as silicate clay, graphite, metal oxide, disulfide and other inorganic materials, which can be prepared by intercalation method. According to different forms of intercalation, it can be divided into the following three methods:
Polymerization intercalation method: The monomers are intercalated into layered silicate sheets and in situ polymerization is initiated. A large amount of heat released during polymerization is used to overcome the force between silicate lamella and make it peel off, so that silicate lamella and polymer matrix are combined in nanometer scale to obtain polymer nanocomposites.
Solution intercalation: A layered filler is immersed in a polymer solution, embedding the polymer directly between inorganic layers. By means of mechanical or thermodynamic action, layered silicates are separated into nanoscale lamellar and dispersed evenly in polymer matrix to form polymer nanocomposites.
Melt intercalation: The polymer is heated to a molten state and inserted directly into a layered inorganic material by mechanical force.
The polymer composite was prepared by melt blending or solution blending of nano-powder and polymer matrix. Blending method is the simplest and most common preparation method of polymer composites, which is suitable for dispersive particles of various forms in polymer. Currently, the commonly used methods are:
Solution blending method: Matrix resin is dissolved in solvent, nano-particles are added and mixed evenly, and the solvent is removed to get composite material.
Emulsion blending method: Add nanoparticles into polymer emulsion and stir evenly to achieve blending.
Melt blending: Nanoparticles are added to the polymer melt body and stirred evenly to achieve blending.
Mechanical blending: Add polymer materials and filler materials to the grinding machine grinding blending.
In addition, LB film synthesis, template synthesis, molecular self-assembly and other preparation methods can also be used to do nanocomposites in some special occasions.