Copolymer vs Homopolymer
Polymers are large molecules, with repeating structural units of monomers. These monomers are bonded to each other with covalent bonds to form the polymer. They have a high molecular weight and consist over 10,000 atoms. In the synthesis process, which is known as polymerization, longer polymer chains are obtained. There are two main types of polymers depending on their synthesis methods. If the monomers have double bonds between carbons from addition reactions, polymers can be synthesized. These polymers are known as addition polymers. In some of the polymerization reactions, when two monomers are joined, a small molecule like water is removed. Such polymers are condensation polymers. Polymers have very different physical and chemical properties than their monomer. Moreover, according to the number of repeating units in the polymer, properties differ. There are a large number of polymers present in the natural environment, and they play very important roles. Synthetic polymers are also used widely for different purposes. Polyethylene, polypropylene, PVC, nylon, and Bakelite are some of the synthetic polymers. When producing synthetic polymers, the process should be highly controlled to get the desired product always. Synthetic polymers are used as adhesives, lubricants, paints, films, fibers, plastic goods, etc.
Monomers are building blocks of polymers. They can be simple or a complex molecule with double bonds or another functional group like –OH, -NH2, –COOH, etc. The unsaturated double bonds or functional groups are needed in the polymerization process, when several monomers are linking to form a polymer. Normally, there are two functional groups in both sides of the monomer, so it can form linear chains by binding to other molecules from both sides. If there are several functional groups, monomers can link to form branched polymers.
When there are two types of monomers joining to make a polymer, that type of polymer is known as a copolymer. This is also known as heteropolymer. Two monomers can join in any fashion to make a polymer. Based on these joining variations, copolymers can be categorized as follows.
- If the two monomers are arranged in an alternative way, it is known as an alternating copolymer. (for example, if the two monomers are A and B, they will arrange like ABABABABAB)
- If the monomers are arranged in any order like AABAAABBBBAB, it is known as random copolymer.
- Sometimes each monomer can join with the same type of monomers, and then the two blocks of homopolymers can join. This type is known as block copolymers (ex: AAAAAAABBBBBBB).
When a single type of monomer is polymerized to form a macromolecule, it is known as a homopolymer. In other words, there is one repeating unit. Polystyrene is a homopolymer where the repeating unit is styrene residues.
What is the difference between Copolymer and Homopolymer?
• In homopolymer, one monomer repeats and forms the whole polymer. In contrast, in copolymers there are two monomers making the polymer.
• Since there are various ways of joining the two monomers, there are different types of copolymers, but this type of variation of joining cannot be seen in a homopolymer.