Homopolymer vs Copolymer: Similarities & Differences
Plastics can be divided into multiple different categories. Each category provides insights into the characteristics, capabilities, and chemical makeup of the material within them. Homopolymers and copolymers have different relationships with their monomers, and those differences can lead to unique qualities in the resulting polymer.
What is a Polymer?
Polymers are chemical compounds consisting of long molecule chains that have bonded together. The smaller individual molecules, called monomers, link to one another forming long molecular chains. Polymers are developed from linking monomers. Plastics are polymers that are formed by combining different monomers together. For example, polyethylene is a polymer made of ethylene (C2H4) monomers.
Homopolymers vs Copolymers
Homopolymers are a type of polymer composed of a single type of monomer. They consist of uniform, repeating molecular chains. The result is a relatively simple structure made of the repeating unit. Homopolymers are usually formed through addition polymerization.
Examples of homopolymers include:
- Polymethyl methacrylate (Acrylic)
Copolymers consist of two or more types of monomers. Copolymers are usually developed using condensation polymerization. Being comprised of multiple monomers, their molecular structures can vary drastically. The type of copolymers is determined by how their monomers organize. Types of copolymers include:
- Alternating copolymers: Monomers are arranged in a repeating pattern (ABABAB).
- Block copolymers: Monomers cluster together to form distinct blocks (AAABBBAAA). Sometimes, monomer composition will slowly transition from one to the other (AAAABBBAABABBAAABBBB). These are known as gradient copolymers.
- Random copolymers: Monomers arranged randomly throughout the polymer (ABAAABBABBBBA). Sometimes, the degree to which monomers react to one another can influence how much of each one is present in a sample. These are called statistical copolymers.
- Graft copolymers: Monomers attach to/branch out from a distinct polymer backbone.
Examples of copolymers include:
- Acrylonitrile butadiene styrene (ABS)
- High Impact Polystyrene (HIPS)
- Polyethylene-vinyl acetate (PEVA)
- Styrene Butadiene (Rubber)
Which is Better?
Homopolymers and copolymers have inherently different polymer chains. How many monomers are used will have a direct influence over how they perform in different environments. Their chemical makeup can make one better than the other depending on the circumstance.
Due to being made up of multiple polymers, copolymers can outperform homopolymers in certain areas. Combining different monomers can allow manufacturers to infuse various qualities together. Generally speaking, copolymers have better chemical resistance and thermal stability than homopolymers.
While having multiple monomers comes with many benefits, there are still reasons to invest in homopolymers. Due to their higher crystallinity, homopolymers tend to have better tensile strength than copolymers. By extension, they also tend to have better creep resistance. Copolymers are capable of meeting many of the same performance standards, but usually require additives or more monomers to do so. Glass-filled copolymers are a very common alternative designed to meet or exceed sophisticated performance requirements.
Choose Between Copolymers vs Homopolymers with Polymershapes
The experts at Polymershapes help industry leaders invest in the best materials for their specific needs. Whether a homopolymer or copolymer works best, our specialists work with world-renowned manufacturers to ensure you get high quality polymers. Contact Polymershapes to learn more about our material options.