oligomersmolecules

An oligomer is a molecule composed of a small number of repeating units, linking together to form a chain shorter than a typical polymer. Oligomers usually contain two to a few dozen monomer units, and their degree of polymerization (DP) is substantially less than that of polymers. Oligomeric species occur across chemistry, biology, and materials science, including oligosaccharides, oligopeptides, and oligodeoxynucleotides.

In synthesis, oligomers can arise when polymerization is stopped early or when chain transfer or terminators are used. Homooligomers consist of the same monomer repeated, while hetero-oligomers contain different monomers. In biological systems, short chains play functional roles, such as peptide hormones or signaling oligosaccharides. In synthetic chemistry, controlled methods such as living/controlled radical polymerization or stepwise coupling enable preparation of oligomers with defined DP and end groups.

Properties depend on DP, composition, and end groups. They are generally more soluble and less viscous than high-DP polymers, with lower melting points and distinct reactivities at chain ends. End-group functionality often governs further coupling or biological recognition. Oligomeric species can also be important in aggregation phenomena; some oligomers are implicated in disease-related aggregates.

Applications include pharmaceuticals and diagnostics (DNA and RNA oligos for sequencing, PCR primers, antisense therapies), materials science (oligomeric precursors for polymers, coatings, surfactants), and catalysis. The term is sometimes used to describe precursors that bridge monomers and polymers in synthesis and in biological contexts as intermediates or functional units. Characterization commonly uses mass spectrometry, chromatography, and spectroscopic methods to determine DP and composition.