oligomer (rus. олигомер) — a substance whose molecules consist several to several dozen similar or different structural units (monomers).

Description

The upper limit of an oligomer’s molecular weight depends on its chemical nature and usually equals the molecular weight of a segment, at which the substance starts demonstrating superelastic strain, forced rubber-like elasticity and other properties inherent to polymers. Polar and rod-like chain oligomers have a greater range of potential molecular weight values (up to 15,000 amu) than nonpolar oligomers (approx. up to 5,000 amu).

Oligomers have a number of properties specific to both monomers and high molecular weight compounds. The physical and chemical properties of adjacent oligomer homologues *) differ much and depend on the nature of their terminal groups; as the molecular weight grows, the influence of terminal groups declines and the difference in properties of adjacent elements becomes less pronounced. Characteristic properties of oligomers include intensive intermolecular interactions, high viscosity and long relaxation time, all of which increase in oligomers with larger molecules.

Reactive oligomers may take part in polymerisation (oligoester acrylates, oligodiens and their co-polymers, epoxy resins, cyclooligoamides, etc.), polycondensation and polyaddition in substances containing carboxylic, aminocyanate, isocyanate and other groups, phenol-formaldehyde, carbamide and alkyd resins, etc.

Oligomers can be obtained through the destruction of high molecular weight polymers in a controlled environment. Oligomers produced by different methods are usually a combination of different homologues. Techniques for producing chemically individual oligomers (i.e. oligomers containing a certain number of monomer units) are based on a staged production process in which a certain reaction product is obtained at each individual stage.

One of the key applications of oligomers is the production of polymer materials and products. Reactive oligomers used for this purpose offer a lot of advantages compared to technology involving the processing of high molecular weight compounds:

- the production of high molecular weight polymer and the manufacture of a product from it may be parts of one operation;

- fluid or low-melting oligomers with high flow in fluid state may be moulded to form a product with no significant effort, without the need for high pressure, temperature or solvents;

- the manufacture of products involves a lot fewer heat effects and less shrinkage, which enables the fluid – solid polymer transition rate to increase.

Oligomers are widely used in the production of plastic foam, varnish, glue and multiple compounds, the treatment of textiles and paper, the production of surfactants, lubricating materials and cellulose fibre materials, and the modification of other polymers, as well as in biology and medicine.


*) A homologue is an element in a sequence of compounds that have similar functional groups and uniform structure and differ from each other by one constant structural element, in this case, a monomer unit.

Authors

  • Khokhlov Alexey R.
  • Govorun Elena N.
  • Nazarov Victor G.

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