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Welcome to the website of the Australian Industrial Chemicals Introduction Scheme (AICIS). We started on 1 July 2020. Read about us.

What is a polymer?

Polymers are used in a variety of everyday products such as plastics, paints, clothing and cosmetic products.

Your industrial chemical is a polymer if it meets both of the following criteria:

1. molecules are distributed over a range of molecular weights (where the difference in molecular weights is due to differences in the number of monomer units)

2. over 50% of the overall weight is made up of sequences of 3 or more monomer units and at least 1 more monomer unit or other reactant that can’t become a repeating unit in the polymer structure (this means over 50% of the substance must be polymer molecules)

Monomer units don’t have to be identical.

Our definitions

Monomer

A chemical that is capable of forming covalent bonds with 2 or more like or unlike molecules under the conditions of a polymer-forming reaction used for a process of polymer formation.

Monomer unit

A reacted form of a monomer in a polymer.

Sequence

A continuous string of monomer units within the molecule that are covalently bonded to one another and are uninterrupted by units other than monomer units.

Polymer molecule

A molecule that contains a sequence of at least 3 monomer units, which are covalently bound to at least one other monomer unit or other reactant (i.e. ‘3+1’ rule).

Other reactant

A molecule that cannot become a repeating unit in the polymer structure.

Examples - reaction between ethylene oxide and phenol to produce ethoxylated phenol

Consider the polymer forming reaction between ethylene oxide and phenol to manufacture an ethoxylated phenol.

A chemical structure diagram of an ethoxylated phenol.

 

 

 

 

Ethoxylated phenol (n is an integer, n≥1)

In this case we regard ethylene oxide as the monomer and phenol as the ‘other reactant’, as it cannot become a repeating unit in the polymer structure. That is, it cannot react with itself or an opened epoxide.

The monomer unit is the opened epoxide -(CH2-CH2-O)-

In this case we regard ethylene oxide as the monomer and phenol as the ‘other reactant’, as it cannot become a repeating unit in the polymer structure. That is, it cannot react with itself or an opened epoxide.

The monomer unit is the opened epoxide -(CH2-CH2-O)-

This chemical meets the definition of a polymer molecule whenever n≥3.

Example 1

Monomer units % by weight of polymer molecules
n=1 0
n=2 0
n=3 100
n=4 0
n=5 0
n=6 0
n=7 0
Sum 100

This substance consists of 100% polymer molecules (n≥3) and therefore meets criterion 2. However, it does not meet criterion 1 as the substance is not distributed over a range of molecular weights. The substance is a discrete chemical. Discrete chemicals have a definite chemical structure that can be represented by a definite molecular formula and chemical structure diagram.

This chemical does not meet our definition of a polymer.

Example 2

Monomer units % by weight of polymer molecules
n=1 40
n=2 20
n=3 15
n=4 12
n=5 8
n=6 5
n=7 0
Sum 100

This substance meets criterion 1 as the substance is distributed over a range of molecular weights. However, it does not meet criterion 2 as the substance consists of less than 50% by weight of polymer molecules, with 60% of the weight being from n=1 and n=2. 

This chemical does not meet our definition of polymer.

Example 3

Monomer units % by weight of polymer molecules
n=1 5
n=2 10
n=3 20
n=4 30
n=5 20
n=6 10
n=7 5
Sum 100

This substance meets criterion 1 as the substance is distributed over a range of molecular weights. The substance also meets criterion 2 as the substance consists of over 50% by weight of polymer molecules, with 15% of the weight being from n=1 and n=2.

This chemical does meet our definition of polymer.

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