Polymerization Reactions

Chemistry II

Types of Polymerization Reactions

• Addition polymerization – monomers are added together, with no other products formed

• Condensation polymerization – small molecule, like water, is formed in the polymerization

Types of Polymers

• Copolymer – Two different monomers form the chain

• Homopolymer – All of the monomers are the same

• Thermoset– when molded to a certain shape it cannot be softened again or dissolved, like Bakelite

• Thermoplastic – can be remelted after molded

Addition Polymerization

• Process initiated by free radical (has unpaired electron)

• Free radical attacks double bond to form a new free radical

• Termination of the reaction occurs when 2 radicals react to form a bond

Condensation Polymerization

• Formation of Nylon dimer• Dimer – two monomers joined• Amino group on left or Acid group on right can

continue to react, extending the polymer

Polymers based on Ethylene

• LDPE – Low Density Polyethylene– Highly branched– Not tightly packed

• HDPE – High Density Polyethylene– Mostly straight-chain molecules– Tightly packed

Examples

• Polypropylene – monomer is propylene, so X is CH3

• Isotactic chain vs. Syndiotactic vs. Atactic

• Polystyrene• Polyvinyl chloride (PVC)