The key difference between copolymer and homopolymer is that there are two monomers making the polymer in copolymers whereas, in homopolymer, only one monomer repeats and forms the whole polymer.
Polymers are large molecules, with repeating structural units of monomers. These monomers bind with each other by covalent bonds to form the polymer. Accordingly, they have a high molecular weight and consist over 10,000 atoms. Furthermore, in the synthesis process (we call it polymerization), we can obtain longer polymer chains. Also, polymers have very different physical and chemical properties than their monomer. Moreover, according to the monomers that we use in the polymerization process, copolymers or homopolymers may form.
CONTENTS
1. Overview and Key Difference
2. What is Copolymer
3. What is Homopolymer
4. Side by Side Comparison – Copolymer vs Homopolymer in Tabular Form
5. Summary
What is Copolymer?
When there are two types of monomers joining to make a polymer, we can call that type of polymer as a copolymer. A synonym for this is heteropolymer. Therefore, two monomers can join in any fashion to make a polymer.
Figure 01: Different types of Copolymers (1-homopolymer, 2- alternating copolymer, 3- periodic copolymer, 4- block copolymer and 5-grafted copolymer).
Depending on these joining variations, we can categorize copolymers as follows.
- If the two monomers arrange in an alternative way, we call it ‘an alternating copolymer’. (for example, if the two monomers are A and B, they will arrange like ABABABABAB)
- If the monomers arrange in any order like AABAAABBBBAB, we call it a random copolymer.
- Sometimes, each monomer can join with the same type of monomers, and then the two blocks of homopolymers can join. We call this type as block copolymers (ex: AAAAAAABBBBBBB).
- Also, periodic copolymers are those that have units arranged in a repeating sequence. For example, (A-B-A-B-B-A-A-A-A-B-B-B)n.
- Furthermore, a graft copolymer contains its main chain consisting of one type of monomer while there are branches attached to this main chain that consists of another monomer.
What is Homopolymer?
When a single type of monomer undergoes polymerization to form a macromolecule, we call it a homopolymer. In other words, there is one repeating unit. For example, polystyrene is a homopolymer where the repeating unit is styrene residues.
Figure 02: A Homopolymer contains only one type of Monomers
Moroever, some common examples for homopolymers include nylon 6, nylon 11, polyethylene, polypropylene, PVC or polyvinyl chloride, polyacrylonitrile, etc.
What is the Difference Between Copolymer and Homopolymer?
In homopolymer, one monomer repeats and forms the whole polymer. In contrast, in copolymer, there are two monomers making the polymer. Hence, this is the key difference between copolymer and homopolymer. Furthermore, another difference between copolymer and homopolymer is that there are different types of copolymers depending on how the two monomers join; there are various ways of joining the two monomers. But, in a homopolymer, this type of variation of joining cannot be seen.
The below infographic presents the difference between copolymer and homopolymer in tabular form.
Summary – Copolymer vs Homopolymer
Polymers are macromolecules formed from monomers. According to the types of monomer that involve in the polymerization, there are two types of polymers. They are the copolymers and homopolymers. The key difference between copolymer and homopolymer is that there are two monomers making the polymer in copolymers whereas, in homopolymer, one monomer repeats and forms the whole polymer.
Reference:
1. Helmenstine, Anne Marie, Ph.D. “Homopolymer Definition.” ThoughtCo, Jun. 22, 2018. Available here
2. “Copolymer.” Wikipedia, Wikimedia Foundation, 17 Sept. 2018. Available here
Image Courtesy:
1.”Copolymers”By Mankash (CC BY-SA 3.0) via Commons Wikimedia
2.”Homopolymer 3D”By Minihaa – Own work (CC0) via Commons Wikimedia