copolymer

A copolymer is a polymer consisting of two or more different monomer species linked together in the same chain. Unlike a homopolymer, which contains a single monomer type, a copolymer incorporates at least two distinct monomer units, which can be arranged in various patterns to modify physical and chemical properties. Copolymers enable combinations of characteristics such as toughness, chemical resistance, and tunable glass transition temperatures that are not readily achieved with a single monomer.

Common architectures include random copolymers, where monomer units are distributed irregularly; alternating copolymers, with a regular ABAB sequence; block copolymers, consisting of contiguous blocks of one monomer followed by blocks of another; and graft copolymers, in which side chains of one monomer are grafted onto a backbone of another.

Copolymerization is typically carried out by addition polymerization of vinyl monomers or condensation reactions that link different functionalities. Controlled or living polymerization methods, such as RAFT or ATRP, allow precise control over sequence, architecture, and molecular weight. The resulting architectures can influence crystallinity, phase behavior, mechanical strength, and chemical compatibility with matrices or fillers.

Notable examples include styrene-butadiene rubber, a random copolymer widely used in tires, and many engineering plastics based on styrene, acrylate, or vinyl ester copolymers. Copolymers are utilized across plastics, elastomers, coatings, adhesives, fibers, and biomedical materials, where tailor-made properties and compatibilization of immiscible components are valuable.

Terpolymers contain three monomer types and are also common in advanced materials. The study of copolymers spans synthesis, characterization, and applications, reflecting their central role in modern polymer technology.