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[1] [2] [3] There are many forms of polymerization [4] and different systems exist to categorize them. IUPAC definition for polymerization. In chemical compounds, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the functional groups present in the reactants [3] and their inherent steric effects.
Chain-growth polymerization or chain-growth polymerisation is a polymerization technique where monomer molecules add onto the active site on a growing polymer chain one at a time. [1] There are a limited number of these active sites at any moment during the polymerization which gives this method its key characteristics.
Combination of two active chain ends: one or both of the following processes may occur. Combination: two chain ends simply couple together to form one long chain (Figure 14). One can determine if this mode of termination is occurring by monitoring the molecular weight of the propagating species: combination will result in doubling of molecular ...
In polymer chemistry, chain transfer is a polymerization reaction by which the activity of a growing polymer chain is transferred to another molecule: [1] [2] + + where • is the active center, P is the initial polymer chain, X is the end group, and R is the substituent to which the active center is transferred.
In chain growth polymerization, two growing chains can collide head to head causing the growth of both of the chains to stop. In the case of radical or anionic polymerization , chain transfer can occur where the radical at the end of the growing chain can be transferred from the chain to an individual monomer unit causing a new chain to start ...
Synthetic methods are generally divided into two categories, step-growth polymerization and chain polymerization. [17] The essential difference between the two is that in chain polymerization, monomers are added to the chain one at a time only, [ 18 ] such as in polystyrene , whereas in step-growth polymerization chains of monomers may combine ...
The easiest way to visualize the mechanism of a step-growth polymerization is a group of people reaching out to hold their hands to form a human chain—each person has two hands (= reactive sites). There also is the possibility to have more than two reactive sites on a monomer: In this case branched polymers production take place.
In polymer chemistry, branching is the regular or irregular attachment of side chains to a polymer's backbone chain. It occurs by the replacement of a substituent (e.g. a hydrogen atom) on a monomer subunit by another covalently-bonded chain of that polymer; or, in the case of a graft copolymer, by a chain of another type.