Addition polymerization is a chain-growth process forming polymers without by-products. It involves initiation by free radicals, cations, or anions, followed by propagation where monomers add to the growing chain, and termination that halts the chain. This method produces polymers such as polyethylene, polypropylene, and PVC, which are vital in various industries. Understanding the detailed mechanism is key to controlling polymer properties.
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Addition polymerization is a type of chain-growth polymerization where unsaturated monomer molecules join together without the loss of small molecules or atoms
Initiation
The first stage of addition polymerization where an active species is formed
Propagation
The second stage of addition polymerization where the active species adds to unsaturated monomers, creating a new active species that adds to more monomers
Termination
The final stage of addition polymerization where the active species is deactivated, halting further chain growth
Addition polymerization does not generate by-products, making it more efficient for certain applications compared to condensation polymerization
Addition polymerization begins with the formation of an active species, such as a free radical, cation, or anion, that initiates the polymerization process
The active species attacks the pi bond of an unsaturated monomer, opening it up and attaching the monomer to the active site, repeating to lengthen the polymer chain
Combination
Termination can occur through combination, where two active chain ends join
Disproportionation
Termination can also occur through disproportionation, where hydrogen is transferred from one chain to another
Chain transfer
Termination can also occur through chain transfer, where the active site is transferred to another molecule
Addition polymerization is used to create polymers such as polyethylene, polypropylene, and PVC, which have a wide range of applications in packaging, construction, and healthcare
Addition polymerization is one of two primary methods of synthesizing polymers, with the other being condensation polymerization, which typically involves the release of small molecules as by-products
The desired properties of the final polymer and the nature of the starting monomers are important factors in determining whether addition or condensation polymerization is used
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The ______ stage of addition polymerization stops the growth of the polymer chain by deactivating the active species.
termination
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Types of active species in addition polymerization
Free radical, cation, or anion; type depends on initiation method.
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Termination mechanisms in addition polymerization
Combination, disproportionation, or chain transfer; ends polymer growth.
