homopolymer

A homopolymer is a polymer in which all repeat units originate from a single kind of monomer. In a homopolymer, every repeating unit has the same chemical composition and sequence, giving a uniform chain along the length. This distinguishes it from copolymers, which incorporate two or more different monomer species within the same chain.

Common examples of homopolymers include polyethylene (from ethylene), polypropylene (from propylene), polyvinyl chloride (from vinyl chloride), polystyrene (from styrene), and poly(methyl methacrylate) (from methyl methacrylate). These polymers are typically prepared by addition polymerization, including radical, anionic, or cationic chain-growth mechanisms, or by ring-opening polymerization of cyclic monomers when the same monomer is used. Some condensation routes can also yield homopolymers when identical monomers repeat, though many widely used polymers form via different chemistries.

The structure of a homopolymer can be linear or branched, depending on the monomer’s functionality. Tacticity—whether the arrangement of side groups is isotactic, syndiotactic, or atactic—affects crystallinity and thermal properties. Regularly arranged monomers (isotactic or syndiotactic) tend to crystallize and exhibit higher melting points or glass transition temperatures than atactic forms, which are typically more amorphous.

Applications of homopolymers span packaging, consumer goods, and engineering plastics, with properties determined by the specific monomer and polymerization conditions. While homopolymers offer predictable behavior, many applications rely on copolymers or polymer blends to achieve a broader range of properties.