Difference Between Oligomer and Polymer

Main Difference – Oligomer vs Polymer

Polymers are macromolecules that are made out of small basic units called monomers. A polymer is formed through a process called polymerization. An oligomer is also a type of polymer. Oligomers are formed when a few number of monomers are linked together via covalent bonds. There are natural and synthetic oligomers and polymers. Both of them are very important in industrial applications. Natural oligomers and polymers can be found in plant extracts, and inside organisms as biochemical compounds. The main difference between oligomer and polymer is that oligomers are formed due to the polymerization of a few monomers whereas polymers are giant molecules formed due to the polymerization of a large number of monomers.

Key Areas Covered

1. What is an Oligomer
      – Definition, Synthesis, Properties, and Examples
2. What is a Polymer
      – Definition, Synthesis, Properties, and Examples
3. What are the Similarities Between Oligomer and Polymer
      – Outline of Common Features
4. What is the Difference Between Oligomer and Polymer
      – Comparison of Key Differences

Key Terms: Covalent Bond, Monomer, Oligomer, Polymer, Polymerization

What is an Oligomer

An oligomer is a complex molecule that is made out of a few monomer units. A monomer is a molecule that can undergo polymerization in order to form a giant molecule. In order to undergo polymerization, a monomer should have a double bond or at least two functional groups. However, these monomers are covalently linked to each other in the polymerization process. This process is called oligomerization.

Figure 1: Acrylated Epoxy Oligomer

When two monomers are linked, it forms an oligomer called a dimer. When three monomers are linked, it forms a trimer. For four monomers, it is a tetramer. Likewise, we can name the oligomers according to the number of monomers present in those complexes.

Oligomers can be made as either homo-oligomers or hetero-oligomers. When identical monomers undergo polymerization, it results in a homo-oligomer. When at least one different monomer undergoes polymerization with these identical monomers, it forms a hetero-oligomer.

When considering about the natural oligomers, many oils are oligomeric. Among synthetic oligomers, plasticizers and polybutene are oligomeric complexes.

What is a Polymer

A polymer is a macromolecule made out of a large number of small units called monomers. These monomers are linked to each other via covalent bonds through a process called polymerization. These polymers have very high masses and densities. They can exist as either linear simple structures or branched complex structures. In the process of polymerization, monomers are linked to each other forming a polymer chain. There are also cross links formed between those polymer chains, which results in a complex 3D structure.

Difference Between Oligomer and Polymer_Figure 2

Figure 2: Polymer chains and the crosslinks between them

Polymers can be classified based on various parameters due to their complexity. The main parameter that can be used for this classification is the type of monomer used in the production of the polymer. If the same type of monomer is used, then the resulting polymer is a homopolymer. If different types of monomers are used, then the resulting polymer is a heteropolymer. Another way to classify polymers is according to their properties. There are three major types of polymers: thermosetting polymers, thermoplastic polymers, and elastomers.

There can be natural polymers and synthetic polymers. Natural polymers include DNA, RNA like polynucleotides, proteins, etc. Synthetic polymers include polymers like PVC, polystyrene, polyethylene. Their chemical and physical properties may vary according to the type of monomers involved in the process of polymerization and the synthesis of polymers.

Furthermore, according to the structure of the polymer, there can be crystalline polymers, semi-crystalline polymers, and amorphous polymers. A crystalline polymer has a well-organized structure whereas amorphous polymers do not have an organized structure. However, almost every polymer has some degree of amorphous structure. Then they are known as semi-crystalline structures.

Similarities Between Oligomer and Polymer

Oligomer and polymer are polymeric structures.
The building blocks of both structures are monomers.
Monomers are linked together through covalent bonds to form oligomers and polymers

Definition

Oligomer: An oligomer is a complex molecule that is made out of a few monomer units.

Polymer: A polymer is a macromolecule made out of a large number of small units called monomers.

Process of Formation

Oligomer: The process of formation of an oligomer is called oligomerization.

Polymer: The process of formation of a polymer is called polymerization.

Number of Monomers Used

Oligomer: Oligomerization uses a very less number of monomers in order to produce an oligomer.

Polymer: Polymerization uses a very large number of monomers in order to produce a polymer.

Mass

Oligomer: The mass of an oligomer is very less comparatively.

Polymer: The mass of a polymer is very high compared to an oligomer.

Conclusion

Both oligomers and polymers are complex molecules that are made out of small units called monomers. These monomers link together via covalent bonds in order to form these complex molecules. The main difference between oligomer and polymer is that oligomers are formed due to the polymerization of a few number of monomers whereas polymers are giant molecules formed due to the polymerization of a large number of monomers.

References:

1. “What is a polymer?” Polymer science learning center, Available here. Accessed 28 Aug. 2017.
2. “Oligomer.” Wikipedia, Wikimedia Foundation, 21 Aug. 2017, Available here. Accessed 28 Aug. 2017.

Image Courtesy:

1. “Acrylated epoxy oligomer en” By Nothingserious (talk) – Own work (Public Domain) via Commons Wikimedia
2. “Polymer Chain – Elastomer” By Koh Wei Teck – Own work (CC BY-SA 4.0) via Commons Wikimedia