What is plasma polymerization? Plasma is a partially ionized gas composed of ions and electrons. It can be produced by a plasma generator that can generate glow discharge (such as high frequency, microwave, etc.). Its electron energy is 1-10 electron volts, the electron density is 10□-10□/ml, and the power is about 50 watts. After the electrons generated by the high-frequency electric field collide with the gaseous organic compound, a "thermal" active species that can undergo plasma polymerization reaction is formed. Generally, the plasma polymerization reaction is under reduced pressure □ (1～1×10_□ Torr, 1 Torr=133.322 Pa), passing the gaseous monomer into the plasma reactor, and polymerizing at room temperature. The polymer is deposited on the reaction plate and can be used to prepare thin films, coatings, etc.

Plasma polymerization is different from general polymerization reactions. The monomers used in plasma polymerization do not have specific functional groups, and the resulting polymer does not have a simple chemical formula weight relationship with the starting monomer. In addition to plasma polymerization of alkenes, alkynes, and diolefins, alkanes (such as ethane, butane, fluoroalkanes, etc.) and aromatics (such as benzene, naphthalene) can also be subjected to plasma polymerization. The results are often branched polymers. For example, the polyethylene obtained by plasma polymerization is obviously different from general polyethylene. The elemental analysis of the plasma-polymerized polyethylene film shows that the H/C ratio is lower than the theoretical value. The theoretically calculated H/C ratio of ethylene monomer is 2, while the ratio of plasma-polymerized polyethylene is about 1.4, indicating the reaction process Dehydrogenation in the formation of branches. No absorption peak (720 cm□) of CH is observed in the infrared spectrum, indicating that it is a non-chain structure. There is no crystalline peak in the X-ray diffraction pattern, indicating that the plasma polymerized polyethylene has a branched structure. It is insoluble in organic solvents, has good high temperature resistance, and does not melt when heated to 300°C.

In addition, plasma-induced polymerization refers to a polymerization reaction in which liquid monomers or monomers dissolved in a solvent are first formed into plasma from gas molecules in a plasma reactor and under the action of an electric field, and then leave the reactor to proceed. Plasma-induced polymerization of methyl methacrylate can obtain ultra-high molecular weight polymethyl methacrylate with a molecular weight of 10 million that can be dissolved in a solvent. Acrylic acid and acrylamide can also be polymerized similarly, but styrene and □-methylstyrene cannot be polymerized.

So we are talking about the problem of plasma polymerization. There are still different opinions most of the time.