Condensation Polymers

Condensation Polymers (Step-Growth Polymers)

• Formed by intermolecular reaction of molecules with a functional group at each end, resulting in the loss of a small molecule such as H2O, alcohol, or HCl.
• Can be formed by the reaction of a single compound with two different functional groups, A and B, or by the reaction of two different compounds, one with two A functional groups and the other with two B functional groups.

Classes of Step-Growth Polymers

• Polyamides
• Polyesters
• Epoxy Resins
• Polyurethanes

Polyamides

• Nylon 6 is an example of a step-growth polymer formed from a monomer with two different functional groups, resulting in the formation of an amide.
• Nylon 6 is formed from the polymerization of 6-aminohexanoic acid, which contains six carbons.
• The starting material for the synthesis of nylon 6 is ε-caprolactam.
• Nylon 66 is an example of a step-growth polymer formed by two different bifunctional monomers, adipoyl chloride and 1,6-hexanediamine.

Polyesters

• Polymers containing many ester groups.
• Dacron is the most common polyester polymer, made by the transesterification of dimethyl terephthalate with ethylene glycol.
• Kodel polyester is formed by the transesterification of dimethyl terephthalate with 1,4-di(hydroxymethyl)cyclohexane.

Epoxy Resins

• They are the strongest adhesives known, being extensively cross-linked systems.
• They can adhere to almost any surface and are resistant to solvents and high temperature.

Addition Polymers

Ring-Opening Polymerizations

• Some compounds can polymerize well, rather than ethylene and substituted ethylenes, in chain-growth polymerizations.
• Epoxides undergo chain-growth polymerization, which can occur by an anionic or cationic mechanism.

Polymerization of Dienes

• The manufacture of rubber involves the polymerization of 2-methyl-1,3-butadiene (isoprene).
• Synthetic rubbers can be made by radical polymerization of dienes other than isoprene.
• Natural and synthetic rubbers can be hardened by vulcanization, which involves heating rubber with sulfur, resulting in cross-linking of the separate polymer chains through disulfide bonds.

Copolymers

• Formed by the polymerization of two or more different monomers.
• Can be classified into four types: alternating, block, random, and graft copolymers.

Anionic Polymerization or Living Polymers

• The initiator is a nucleophile that reacts with the monomer to form an anion propagating site.
• The mechanism involves an initiating step and propagation steps.
• Living polymers are most common in anionic polymerization because the chains cannot be terminated by proton loss or by chain combination or disproportionation.
• Examples of alkenes that undergo anionic polymerization include methyl α-cyanoacrylate, which is used to make Super Glue.

Learn about condensation polymers, also known as step-growth polymers, formed through intermolecular reactions of molecules with functional groups at each end.