Explain how polymers can be distinguished based on the types of monomers that they are composed of. The two types of polymers are homopolymers and copolymers. A homopolymer is a polymer that is composed of a single type of monomer. A copolymer is a polymer that is composed of two or more different monomers connected over and over.
Show the students how to write out the molecular formulas for polymers. Although polymers are formed from the same types of elements as smaller compounds, their large size makes it difficult to write down each and every molecule that is present within the polymer. The shorthand for writing polymers is to put the repeating unit in parentheses, with dashes on each end. This indicates that the unit is repeating. An example is (-CH2-).
Use molecular models to demonstrate the different structural conformations of polymers. When polymers have substituents, the way in which the substituents lie on the chain provides different classification to the polymers. When the substituents lie on the same side of the polymer, the polymer is referred to as isotactic. When the substituents are alternating in a pattern from one side to the other, then the polymer is syndiotactic. When the substituents are in a random fashion, the polymer is atactic.
Discuss how polymers can be organized based on their method of synthesis. Two such categories of polymers are addition polymers and condensation polymers. Addition polymers are formed by the addition of the monomers, and without the loss of any other molecules. Condensation polymers are formed from the addition of the monomers and with the loss of a molecule, such as water.
Explain how addition polymers and condensation polymers have different properties. Addition polymers generally have a shorter reaction time than do condensation polymers. Also, addition polymers typically have a lower molecular weight than the condensation polymers.
List and describe some of the general reactions of polymers. The main categories of reactions are radical polymerization and condensation reactions. Radical polymerization involves the breaking of a chemical bond with heat, which results in the formation of a compound with a lone electron. This electron then reacts with another compound. The condensation reaction involves the addition of two polymer units, with the loss of water as a product.
Explain how polymers can be classified based on their physical properties when heated. Thermosets are polymers that, when heated, become soft, yet then harden. Reheating them will not cause them to become soft again. Thermoplastics are the types of polymers that, when heated, become soft, and then harden when they are cool. These types of polymers will become soft again when they are heated.