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The power of transformation of polymers: Do you know how active cation polymerization achieves ultra-low molecular weight distribution?
In polymer science, active cationic polymerization has become an important technology, and the principles behind it may surprise many people.This polymerization technology not only enables the synthesis of polymers with very clearly defined but also achieves a low molecular weight distribution, the importance of which is that it can create polymers with unusual structures such as star-shaped polymers and block copolymers. .This technology has attracted widespread interest in both business and academia.
Active cationic polymerization is the key to achieving an ordered structure by controlling the active charge species in the polymerization reaction.
Basic Concept
In cationic polymerization, the active site of the polymer chain is a carbo-positive ion, and corresponding counterions are present nearby.The basic steps of its reaction include chain growth, chain termination and chain transfer.In active cationic polymerization, chain growth represents the access of a monomer, such as aliphatic hydrocarbon or ethylene, thereby increasing the length of the polymer.
The active reaction between carbo-positive ions and monomers is the key to polymer growth.
The termination or transfer of the chain, although there is, in an ideal active system, a chemical equilibrium is reached between the active cation and the dormant covalent species, and its exchange rate must be faster than the polymerization rate.
Historical Background
The development of active cation polymerization began in the 1970s and 1980s.Japanese scholar Higashimura first made a breakthrough in polymerizing p-methoxystyrene. In subsequent research, Kennedy and Faust discussed the polymerization reaction of methylstyrene and boron trichloride in 1982.These contributions laid the foundation for active cationic polymerization and promoted the rapid development of polymer engineered polymers.
Isobutylene Polymerization
The active polymerization of isobutene is usually carried out under conditions below 0°C, using a mixing system of non-polar and polar solvents.Although the molecular weight of the polymer can reach 160,000 g/mole and the polydispersion index can be as low as 1.02, it is crucial to choose the right solvent due to the polymer solubility problem.
Vinyl chloride polymerization
Vinyl chloride is a very reactive monomer.I2/HI or zinc salt catalysts are mostly used in production. Compared with other polymerization technologies, vinyl chloride polymerization provides greater flexibility.
Active cationic cyclic start polymerization
In this process, the polymer starts with a monomer with a heterocyclic structure that is easy to open ring-like.However, since heterologous atoms may have a nucleophilic attack on the growing polymer chain, the difficulty of completing this process is increased.Strong electronegative initiators such as trifluoroacetic acid can be used to improve the efficiency of polymerization.
Active cationic polymerization allows researchers to have a deeper understanding of the relationship between the structure and performance of polymers.
Current and future applications
With the continuous development of active cation polymerization, its application scope has gradually expanded.From medical supplies to high-performance materials, active cation polymerization technology has shown amazing potential in the fields of materials science and biomedicine.In addition, as environmental demand increases, this technology may also be used to develop more environmentally friendly polymer products.
Active cationic polymerization technology is not only a major breakthrough in the field of materials science, it also challenges our traditional concepts about polymer synthesis.In the future, with the continuous advancement of technology, can we expect to see more polymer innovations targeting environmental and functional needs emerge?
