Which is one of the simplest synthetic polymers? How does it react?

What is the process by which polymers are broken down into monomers?  What is added to the polymers during the reaction (what goes into the reaction?)

What is the process by which monomers are joined together to form polymers? What is removed from the monomers during the reaction (what comes out of the reaction)?

Consider a hypothetical tough polymer that exhibits exceptional mechanical properties. This polymer possesses high strength and toughness, allowing it to withstand extreme conditions. Discuss the underlying polymer chemistry principles that contribute to the toughness of this material.