page_title: Polymer
section_title: Synthesis
hierarchical_section_title: Polymer / Synthesis
caption_attribution_description: English: A classification of the polymerization reactions: Step-growth, Chain and others. Modified from original CC figure on Polymer Wiki page by replacing "chain-growth" to "chain"
context_page_description: A polymer
  is a substance or material consisting of very large molecules, or macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and natural polymers play essential and ubiquitous roles in everyday life. Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous and semicrystalline structures rather than crystals.
  The term "polymer" derives from the Greek word πολύς and μέρος, and refers to large molecules whose structure is composed of multiple repeating units, from which originates a characteristic of high relative molecular mass and attendant properties. The units composing polymers derive, actually or conceptually, from molecules of low relative molecular mass.
context_section_description: Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network. During the polymerization process, some chemical groups may be lost from each monomer. This happens in the polymerization of PET polyester. The monomers are terephthalic acid (HOOC—C₆H₄—COOH) and ethylene glycol (HO—CH₂—CH₂—OH) but the repeating unit is —OC—C₆H₄—COO—CH₂—CH₂—O—, which corresponds to the combination of the two monomers with the loss of two water molecules. The distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue.
  Synthetic methods are generally divided into two categories, step-growth polymerization and chain polymerization. The essential difference between the two is that in chain polymerization, monomers are added to the chain one at a time only, such as in polystyrene, whereas in step-growth polymerization chains of monomers may combine with one another directly, such as in polyester. Step-growth polymerization can be divided into polycondensation, in which low-molar-mass by-product is formed in every reaction step, and polyaddition.
  Newer methods, such as plasma polymerization do not fit neatly into either category. Synthetic polymerization reactions may be carried out with or without a catalyst. Laboratory synthesis of biopolymers, especially of proteins, is an area of intensive research.
caption: A classification of the polymerization reactions
exif: {}