A macromolecule is a very large molecule important to biological processes, such as a protein or nucleic acid. It is composed of thousands of covalently bonded atoms. Many macromolecules are polymers of smaller molecules called monomers. The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, and carbohydrates) and large non-polymeric molecules such as lipids, nanogels and macrocycles. Synthetic fibers and experimental materials such as carbon nanotubes are also examples of macromolecules.
Polyaddition (or addition polymerisation ) is a polymerization reaction that forms polymers via individual independent addition reactions. Polyaddition occurs as a reaction between functional groups on molecules with low degrees of polymerization, such as dimers, trimers and oligomers, to form species of higher molar mass. Only at nearly complete conversions does the polymer form, as in polycondensation and in contrast to chain polymerization. A typical polyaddition is the formation of a polyurethane.
A sequence-controlled polymer is a macromolecule, in which the sequence of monomers is controlled to some degree. This control can be absolute but not necessarily. In other words, a sequence-controlled polymer can be uniform (its dispersity Ð is equal to 1) or non-uniform (Ð>1). For example, an alternating copolymer synthesized by radical polymerization is a sequence-controlled polymer, even if it is also a non-uniform polymer, in which chains have different chain-lengths and slightly different compositions.
A polyamide is a polymer with repeating units linked by amide bonds. Polyamides occur both naturally and artificially. Examples of naturally occurring polyamides are proteins, such as wool and silk. Artificially made polyamides can be made through step-growth polymerization or solid-phase synthesis yielding materials such as nylons, aramids, and sodium polyaspartate. Synthetic polyamides are commonly used in textiles, automotive industry, carpets, kitchen utensils and sportswear due to their high durability and strength.
An atom is a particle that consists of a nucleus of protons and neutrons surrounded by a cloud of electrons. The atom is the basic particle of the chemical elements, and the chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium, and any atom that contains 29 protons is copper. The number of neutrons defines the isotope of the element. Atoms are extremely small, typically around 100 picometers across.
