- This article is about the properties and structure of macromolecules. For species, see polymers .
A macromolecule is a molecule with a high molecular weight , the structure of which is a multiple repetition of units formed (in fact or mentally) from molecules of small molecular weight. The number of atoms that make up macromolecules can be very large (hundreds of thousands and millions).
High-molecular substances are usually considered to have a molecular weight of more than 10 3 Da . Whether the molecular weight is large enough for a molecule to be considered a macromolecule is often (but not always!) Determined by the following criterion: if adding or removing one or several units does not affect the molecular properties, the molecule can be considered a macromolecule (this criterion turns out to be unsuccessful, for example, in the case of biopolymers ).
As synonyms "macromolecules" are used "polymer molecule" or "mega molecule".
The term “macromolecule” was introduced by Hermann Staudinger in 1922 ( Nobel Prize in Chemistry (1953)).
Conformations
A polymer ball is not the same as a reeled ball of yarn. The polymer coil ( English coil ) is more like a tangled thread formed by random kicks of an unwinding reel around the room. Polymer ball continuously changes its conformation (spatial configuration). The typical form of a coil looks similar to the trajectory of the Brownian motion (a special case, the so-called perfect coil, is described by the same equations). The formation of coils occurs due to the fact that the polymer chain at a certain distance (statistical segment) "loses" information about its direction. Accordingly, it is possible to speak about a coil when the contour length of a chain considerably exceeds the length of a statistical segment.
The globular conformation of the polymer chain is a dense conformation in which the polymer volume fraction is comparable to unit (if the polymer fraction is close to unity, the globule is called dense; if the polymer volume fraction is comparable, but much smaller than unity, then the globule is said to be loose) . The globular state is realized when the interaction of polymer links with each other and with the environment (for example, with a solution) leads to the mutual attraction of the links.
See also
- Macromolecule configuration
Literature
- Elias G.-G. Megamolecules. - L .: Chemistry, 1990. - 272 p.
- A. Simon. Particle World: Colloid Chemistry for All. - M .: Science, 1987. - 167 p.
- Grosberg A. Yu. , Khokhlov A. R. Statistical physics of macromolecules. - M .: Science, 1989. - 344 p.