copolymerizing

Copolymerizing is the chemical process of forming a polymer that contains two or more different monomer units within the same macromolecule. By combining monomers with distinct chemical and physical properties, copolymers can exhibit properties not attainable with a single monomer, such as modified glass transition temperature, improved toughness, chemical resistance, or altered processability.

Common types include random copolymers (monomer units distributed without a regular sequence), alternating copolymers (strict ABAB... sequence), block copolymers (long blocks of one monomer followed by blocks of another), and graft copolymers (side chains of one monomer grafted onto a backbone of another). Some copolymers are statistical or designed with specific sequencing.

Polymerization methods vary. Free-radical copolymerization is widely used for vinyl monomers; living ionic or coordination polymerizations enable more precise architectures such as well-defined block copolymers. Catalysts such as Ziegler–Natta or metallocenes can enable stereoregular copolymers and controlled sequence distribution.

A key concept for composition control is the reactivity ratios of the monomers, r1 and r2, which determine how often each monomer adds relative to the other, described by the Mayo–Lewis equation. This governs copolymer composition and sequence distribution.

Examples and applications include styrene–butadiene copolymers (SBR) used in tires; acrylonitrile–butadiene–styrene (ABS) plastics; ethylene–vinyl acetate (EVA) in packaging and films. Copolymerization remains a fundamental strategy for tailoring mechanical, thermal, and chemical properties in plastics, elastomers, and advanced polymers.