Main Difference – Homopolymer vs Copolymer
Polymers are the macromolecules formed by linking of a large number of small units called monomers through chemical reactions. The process of formation of polymers is called polymerization. The chemical and physical properties of a polymer mainly depend on the type of monomer or monomers used to form the polymer. Based on the number of different types of monomers used to form a polymer molecule, there are two types of polymers: homopolymers and copolymers. The main difference between homopolymer and copolymer is that homopolymers are produced by using a single type of monomer, whereas copolymers are formed by using two different types of monomers. Because of this difference, both homopolymers and copolymers gain their unique set of properties.
This article explores,
1. What is a Homopolymer?
– Definition, Formation, Structure and Characteristics
2. What is a Copolymer?
– Definition, Formation, Structure and Characteristics
3. What is the difference between Homopolymer and Copolymer? 
What is a Homopolymer
A homopolymer is formed by a single type of monomer. Thus, it consists of only one type of repeating unit. homopolymers are usually made by a polymerization technique called addition polymerization. Monomers that undergo this process must have either double or single bonds. The repeating unit enclosed in brackets represents the chemical structure of a homopolymer. For example, if we take ‘X’ as the repeating unit of a particular homopolymer, we can represent the structure of that homopolymer as –[X]-n. Usually, when naming the homopolymers, the word ‘poly’ is used as the prefix in most cases, followed by the chemical name of the repeating unit. For example, repeating unit ‘vinyl chloride’ forms a polymer called polyvinyl chloride (PVC). Some common examples of homopolymers include polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, and poly(methyl methacrylate).
What is a Copolymer
A polymer formed from more than one type of monomer is called a copolymer. Thus, it contains two or more different types of repeating units. Usually, most of the copolymers are formed through a process called condensation polymerization. There are several classes of copolymers: block copolymers, alternating copolymers, graft copolymers, and statistical copolymers. The structure of these classes can be explained simply by using two types of hypothetical repeating units namely; A and B. In statistical copolymers, the sequence of repeating units obeys known statistical laws. Random copolymers are an example for statistical copolymers that have a random distribution of repeat units (ex: ̴ ̴ A-B-B-A-A-A-A-B-B-B-A-B-B ̴ ̴). Alternating copolymers consist of only two types of repeat units, which are arranged alternative along the polymer chain (Ex: ̴ ̴ A-B-A-B-A-B-A-B-A- B ̴ ̴). In block copolymers, the repeat units exist in blocks of the same type (ex: ̴ ̴ A-A-A-A-A-B-B-B-B-B ̴ ̴). Block copolymers are linear copolymers. Graft copolymers contain branches of different chemical structures attached to main chain. Some common copolymers include poly(vinyl acetate), poly (ethylene oxide), poly(ethylene terephthalate) and poly(hexamethylene sebaacamide).
Structure of the condensation polymerization between Formaldehyde and Phenole to Bakelite
Difference Between Homopolymer and Copolymer
Definition
Homopolymers consist of single species of repeating units.
Copolymers consist of two or more type of repeating units.
Amount of Monomer Species
Homopolymers have a single type of monomer.
Copolymers have two or more types of monomers.
Chemical Structure
Homopolymers usually have a simple structure.
Copolymers have a complex structure.
Polymerization Process
Homopolymers are formed through addition polymerization.
Copolymers are formed through condensation polymerization.
Examples
Homopolymers include PVC, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, and poly(methyl methacrylate).
Copolymers include poly (vinyl acetate), poly (ethylene oxide), poly(ethylene terephthalate) and poly(hexamethylene sebaacamide).
References:
“Polymerisation of Ethylene” – derived by Polymérisation de l’éthylène By Cjp24 – Own work (Public Domain) via Commons Wikimedia
“Polykondensation Bakelit 1.” By MaChe (talk) – Own work (Public Domain) via Commons Wikimedia
