Surface grafting polymerization is an effective technique for preparing high-performance materials by reacting the active sites on the surface of materials with the target grafted monomers or polymers. Surface grafting polymerization mainly includes atom transfer radical polymerization (ATRP), ultraviolet grafting polymerization, and plasma induced grafting polymerization. The surface graft polymerization method has high chemical stability and can accurately control the graft chain length, graft density, and graft position. In addition, this method also has strong applicability.

Introduction to Plasma

At a certain pressure, as the temperature increases, the solid state changes to liquid state, and then to gas state. Some can also directly change from solid state to gas state. People have found that as the temperature of gas substances continues to rise, the thermal motion of gas molecules becomes increasingly intense. When the temperature is high enough, the atoms that make up the molecules gain sufficient kinetic energy and begin to ionize each other, causing the molecules to split into atoms. At this point, if the temperature is further increased, another new phenomenon will occur. The outermost electrons of the atoms break free from the constraints of the atomic nucleus and become free electrons, ultimately causing the molecules and even atoms that make up the gas to become charged ions. This ionized gas, composed of electrons, ions, free radicals, excited states of molecules and atoms, has equal positive and negative charges and does not exhibit electrical properties to the outside world macroscopically. Therefore, it is called plasma. Its formation process is shown in Figure 1, which is a continuation of solid, liquid, and gas. Another aggregation state after the state is called the fourth state of matter. Plasma is an ionized gaseous substance containing electrons, ions, and neutral particles with a certain energy distribution. When it collides with the surface of a material, it transfers its energy to the molecules and atoms on the surface of the material, resulting in a series of physical and chemical processes.

Plasma induced graft polymerization

Plasma induced graft polymerization is a method for improving the surface properties of polymer materials, which involves generating free radicals on the surface of the polymer material using plasma, and then polymerizing with monomers containing unsaturated bonds to form graft chains. This method does not require polymerization in plasma and can be carried out under different conditions such as gas phase, liquid phase, or simultaneous radiation. In this method, the gas-phase method involves converting the monomer into a gaseous state and allowing the polymer material to come into contact with the plasma treated substance for graft polymerization; The direct liquid-phase method involves immersing plasma treated polymer materials in liquid monomers for graft polymerization; The atmospheric pressure liquid-phase method involves first exposing the plasma treated polymer material to air to convert surface free radicals into peroxides, and then placing it into liquid monomers for graft polymerization; The radiation law is to first adsorb monomers onto the surface of polymer materials, and then place them in plasma for graft polymerization. These four methods can all achieve plasma graft polymerization of polymer materials, but each has different characteristics.

Method of plasma grafting modification

The advantage of plasma induced grafting method is its wide applicability, which can treat various polymer materials without damaging the properties of the matrix itself. The plasma itself can act as an initiator without the need to add other chemical initiators, thereby reducing the amount of chemical reagents and making it more environmentally friendly. In addition, the plasma induced grafting polymerization method is easy to operate and time-consuming.