18.3.1 Addition Polymers

• What are addition polymers formed from?

  Small, repeating monomers
• Addition polymers are formed from alkenes when their double bonds are converted into single bonds.
• Chain initiation in addition polymerization requires free radicals.
• What happens during chain propagation in addition polymerization?

  The chain extends
• Chain termination in addition polymerization occurs when all free radicals are removed or combined.
• Addition polymers are typically biodegradable.

  False
• What is the main difference between addition and condensation polymers?

  Atom loss during formation
• Addition polymers are formed when small, repeating units called monomers join together without losing any atoms.
• Arrange the steps of chain initiation in addition polymerization:

  1️⃣ An initiator breaks down to form free radicals

  2️⃣ Free radicals attack alkene monomers

  3️⃣ A new free radical is formed
• What is an example of an initiator used in chain initiation?

  Peroxides
• Free radicals have an unpaired electron.
• Chain propagation in addition polymerization occurs when a free radical attacks an alkene monomer to form a new bond.
• What is the second step in addition polymerization?

  Chain propagation
• In chain propagation, a free radical attacks an alkene monomer to form a new covalent bond
• Steps in chain propagation during addition polymerization

  1️⃣ Free radical attacks an alkene monomer

  2️⃣ New covalent bond forms

  3️⃣ Another free radical is generated

  4️⃣ Chain extends with repeated reactions
• A free radical is a reactive species with an unpaired electron.
• What is the final step in addition polymerization called?

  Chain termination
• In combination, two free radicals react to form a covalent bond
• Disproportionation involves the transfer of a hydrogen atom from one chain to another.
• What are addition polymers formed from?

  Double or triple bonds
• Addition polymers are formed when small, repeating units called monomers join together without losing any atoms
• During the formation of addition polymers from alkenes, double bonds in the monomers are broken to form new single bonds.
• What is the process called when monomers join to form a long chain in polymers?

  Addition polymerization
• Monomers used in addition polymerization are alkenes with carbon-carbon double
• Addition polymerization involves the loss of atoms.

  False
• Describe the process of addition polymerization in terms of bond changes.

  Double bonds become single bonds
• Chain initiation in addition polymerization begins with the generation of free radicals.
• Peroxides are commonly used as initiators in chain initiation.
• Steps in chain initiation in addition polymerization

  1️⃣ Initiator breaks down to form free radicals

  2️⃣ Free radicals attack alkene monomers

  3️⃣ New free radicals are formed
• What is the second step in addition polymerization called?

  Chain propagation
• During chain propagation, a free radical attacks an alkene monomer to extend the chain.
• Chain propagation involves the continuous formation of new free radicals.
• What are the two main mechanisms of chain termination in addition polymerization?

  Combination and disproportionation
• Disproportionation in chain termination involves the transfer of a hydrogen atom between chains.
• Combination in chain termination results in two chains combining through a covalent bond.
• Name three common addition polymers.

  Polyethene, polypropene, PVC
• Polyethene is used in shopping bags and food packaging.
• Polypropene is commonly used in car bumpers and textiles.
• Match the monomer with the corresponding polymer:

  Ethene ↔️ Polyethene

  Propene ↔️ Polypropene

  Vinyl chloride ↔️ PVC

  Styrene ↔️ Polystyrene
• Describe the properties of polyethene.

  Low strength, high flexibility