Analysis on the layer-by-layer assembly process technology in filter membrane surface coating

Layer-by-layer (LbL) assembly is a widely used technology to modify the surface properties of filter membranes by depositing alternating layers of different materials onto the membrane surface. It allows for precise process control and can enhance its targeting The performance of specific filtration applications, control standards for the thickness, composition and functionality of the filter membrane can reach the nanoscale. One of the main advantages of LbL assembly technology is its versatility, it can be used with a variety of materials, including polymers, proteins , nanoparticles, and even some small organic molecules, etc., their wide application and accuracy give them great advantages in customizing membrane properties.

What is the principle of the layer-by-layer (LbL) assembly process? LbL assembly begins by immersing the membrane in a solution containing positively charged materials (often called polycations), which interact with the negatively charged membrane surface through electrostatic interactions. A monolayer of polycations is formed on the surface of the membrane, and the process is repeated by immersing the membrane in a solution containing a negatively charged material (polyanions), which interacts with the positively charged polycation layer to form a layer on top of the previous layer. For additional layers, the deposition process can be repeated multiple times, each layer is deposited one layer at a time, and the charge of each layer drives the adsorption of the next layer. This process is achieved by generating strong electrostatic attraction between the layers, although there are also Other forces such as hydrogen bonds, van der Waals forces, or hydrophobic interactions may be involved, but these are insignificant in the face of electrostatic attraction.

The basic process of LbL assembly consists of the following steps:

For layer deposition, the membrane is immersed in a solution containing the first layer material (polycation or polyanion), then the substrate is removed and rinsed to remove excess material.

Built layer by layer, the membrane is immersed in a solution containing a second layer of material (oppositely charged to the first layer's material). The process is repeated sequentially by immersing the modified membrane into a solution containing the next layer of material, with each subsequent layer passing Complementary interactions between materials adhere to previously deposited layers, and the number of layers can be controlled based on the desired film properties.

Performance control, the LbL assembly process can control the performance of the modified membrane, on the one hand by controlling the number of layers above, and on the other hand by selecting materials with specific functions, etc., to improve the filtration efficiency, improved selectivity, and increased stability of the membrane. properties or customized surface properties.

LbL assembly technology provides a molecularly controlled method for surface modification of filtration, which allows precise control of layer thickness, composition, and performance, and the deposited layers can provide additional functions to the filtration membrane, such as membrane selectivity, enhanced Stability or altered surface chemical properties, etc., and the process's ability to incorporate a variety of materials, including polymers, nanoparticles, or biomolecules, has enabled it to achieve a wide range of applications in industries such as filtration and separation.