Liitumispolümeriseerimine

Liitumispolümeriseerimine is a type of polymerization reaction where monomer molecules add to one another in such a way that the polymer contains all the atoms of the monomer unit. This process typically occurs through a chain mechanism involving initiation, propagation, and termination steps. Unlike condensation polymerization, no small molecules like water or methanol are eliminated during the reaction.

The monomers involved in addition polymerization usually contain double or triple bonds, which are reactive sites for the chain growth. Common examples of monomers that undergo addition polymerization include alkenes like ethylene, propylene, and styrene. The most prevalent types of addition polymerization are free-radical polymerization, cationic polymerization, and anionic polymerization.

Free-radical polymerization is initiated by free radicals, which are species with an unpaired electron. These radicals attack the double bond of a monomer, forming a new radical that can then add to another monomer, and so on. Cationic polymerization is initiated by cations, while anionic polymerization is initiated by anions. The choice of initiator depends on the nature of the monomer and the desired polymer properties.

Addition polymerization is widely used in the industrial production of many common plastics, such as polyethylene, polypropylene, and polyvinyl chloride (PVC). These polymers have diverse applications ranging from packaging and textiles to construction materials and automotive parts. The control over reaction conditions, such as temperature, pressure, and the presence of catalysts or inhibitors, allows for the tailoring of polymer molecular weight and microstructure, influencing the final material properties.