Polimeres

Polimeres (polymers) are large molecules composed of repeating subunits called monomers linked by covalent bonds. They occur naturally, such as cellulose, proteins, nucleic acids, starch, and natural rubber, and synthetically, such as polyethylene, polypropylene, polystyrene, poly(vinyl chloride), nylons, and polyesters. The properties of a polimere depend on the monomers used, the chain length, and the way chains are arranged (linear, branched, or crosslinked).

Polimeres are formed by polymerization, which can be addition (chain-growth) or condensation (step-growth). In addition polymerization, unsaturated monomers join to form long chains with minimal byproducts. In condensation, monomers combine with the elimination of small molecules such as water or methanol. Molecular weights typically range from thousands to millions of g/mol. Chain architecture and tacticity influence crystallinity, strength, and melting temperature.

Classification includes thermoplastics, which soften upon heating; thermosets, which are permanently crosslinked; and elastomers, which are highly elastic. Biopolymers are produced by living organisms; synthetic polymers are manufactured industrially. Applications span packaging, textiles, automotive and aerospace parts, electronics, medical devices, and coatings. Environmental considerations include recycling, persistence in ecosystems, and concerns about microplastics; research aims to improve recyclability and develop biodegradable or compostable alternatives. The field has a long history, with early 20th-century work by scientists such as Hermann Staudinger establishing the macromolecular nature of polymers.