polymeres

Polymeres are large molecules built from repeating units called monomers. Natural polymeres include DNA, proteins, cellulose, and starches, while synthetic polymeres include polyethylene, polystyrene, nylon, and polyvinyl chloride. In chemistry and materials science, polymeres are characterized by high molecular weight and long-chain architecture, with properties determined by chain length, architecture, and composition.

Polymeres can be linear, branched, or crosslinked. Stereochemistry (tacticity) and crystallinity influence melting points, stiffness, toughness, and solubility. Thermal and mechanical properties arise from intermolecular interactions and the mobility of the chains.

Polymeres form by polymerization, which occurs mainly via two general routes: chain-growth (addition) polymerization and step-growth (condensation) polymerization. Chain-growth mechanisms include free-radical, cationic, anionic, and coordination polymerization, where monomers add sequentially to a growing chain. Step-growth polymerization yields polymers from multifunctional monomers with small-molecule byproducts, as seen in polyesters, polyamides, and polyurethanes.

Polymeres are commonly categorized as thermoplastics, thermosets, or elastomers. Thermoplastics soften upon heating and can be reprocessed, thermosets form permanent networks that do not melt, and elastomers are rubbery with low glass transition temperatures. Widely used polymeres include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyesters, nylons, and polycarbonates. Biopolymers and biodegradable polymeres such as polylactic acid (PLA), poly(glycolic acid) (PGA), and polyhydroxyalkanoates (PHA) have applications in medicine and sustainability.

Historically, polymer science advanced in the 20th century, led by researchers such as Hermann Staudinger, who proposed the macromolecular concept. Today, polymeres underpin a broad range of technologies, with ongoing research in synthesis, structure–property relationships, and environmental impact, including recycling and degradation challenges.