Chemistry » Chemistry 112: Organic Molecules » Plastics And Polymers

What is a polymer?

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What is a polymer?

Polymers are large molecules (macromolecules) that are made up of many repeating structural units called monomers which have various functional groups. To put it more simply, a monomer is like a building block.

Fact:

Mono means one, while poly means many. So a monomer is the single unit, and a polymer is made from many monomers.

Definition: Monomer

A monomer is a small molecule that can be combined through a reaction to form a polymer. It is a repeating unit in the polymer.

When lots of monomers are joined together by covalent bonds, they form a polymer.

Definition: Polymer

Polymer is a term used to describe large molecules consisting of repeating structural units (monomers) connected by covalent chemical bonds.

Tip:

A polymer consists of a backbone, made up of repeating units.

What is a polymer?

In an organic polymer, the monomers are joined by the carbon atoms of the polymer backbone or chain. A polymer can also be inorganic, in which case there may be atoms such as silicon in the place of carbon atoms. We will look solely at organic polymers. Polymers are a specific group of macromolecules. A macromolecule is any compound with a large number of atoms. A biological macromolecule is one that is found in living organisms. Biological macromolecules include molecules such as carbohydrates, proteins, nucleic acids and lipids. They are essential for all known forms of life to survive.

Definition: Macromolecule

A macromolecule is any molecule containing a large number of atoms.

The key feature that makes a polymer different from other macromolecules is the repetition of identical or similar monomers in the polymer chain. Polymers will contain chains of the same type of functional group and that functional group is dependent on the monomer used. The examples given over the following pages will help to make these concepts clearer. Plastics are a group of polymers that can be molded during manufacture. They can be one polymer or a blend (mixture) of polymers and may contain other substances as well. These other substances can be inorganic (e.g. used for electronic packaging) or stabilising (e.g. used for increasing fire resistance).

Definition: Plastic

A subgroup of organic polymers that can be molded. Plastics may contain more than one organic polymer as well as other additives.

Fact:

A thermoplastic is a plastic that can be heated and molded multiple times without changing chemically.

What is a polymer?

The learners should come back to the What is a polymer? concept map throughout this section, whenever they have new information to add. This can then be used as a study tool.

Optional Activity: What is a polymer?

  1. SASOL polymers is the largest division of the Johannesburg based companies’ chemical business. Divide the class into 4 groups and have each group research the production of polymers in South Africa, including investigations into one of the products listed below:

    • Kevlar and Mylar

    • Windscreens

    • Break pads

    • Polymers to replace glass

    Research the functions of the materials, who invented or discovered them, and what they are made of. Present your findings to the rest of the class in a five minute discussion.

  2. Read this section (What is a polymer?) carefully. Research any concepts you don’t understand and draw up a concept map (mindmap) describing what a polymer is.

    A concept map is a way of showing concepts and linking knowledge using graphics. An example is given below:

    What is a polymer?

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