Question

Describe the formation of polystyrene.

Short answer

Polystyrene is created from the monomer styrene through a process known as chain-growth polymerization. An initiator starts the reaction, causing the styrene molecules to bond together into a chain. The process stops when two chains combine, when a chain reacts with an initiator molecule, or when a chain folds back on itself, forming the final polystyrene product.

Step-by-step solution

Understand the Basic Building Block

Polystyrene is formed from the monomer styrene, a liquid hydrocarbon that is chemically reacted to make polystyrene. The styrene molecule is composed of a benzene ring attached to a vinyl group, which consists of 2 carbon atoms double-bonded to each other, with one of them also bonded to a hydrogen atom.

Explain the Polymerization Process

Polystyrene is created through a process known as chain-growth polymerization. This involves an initiator, which is a compound that triggers the chemical reaction. The initiator joins onto one of the vinyl group's carbon atoms to start the reaction. The bond between the two carbons breaks, leaving one carbon bonded to the initiator and the other carbon with an unpaired electron.

Describe Chain Formation

The styrene molecule with the unpaired electron, known as a radical, can now bond with another styrene molecule, induced by heat or another type of energy. This causes the second styrene molecule's vinyl bond to break and form a bond with the first styrene molecule, creating a chain. This process continues, with each new styrene molecule joining the end of the chain and breaking its vinyl bond to make a place for the next styrene molecule.

Describe Chain Termination

Eventually, the reaction stops when two chains combine, when a chain reacts with a molecule of the initiator, or when a chain folds back on itself to form a ring. At this point, we have a long chain molecule of polystyrene.