Chemical Structure
In order to understand the structure of acrylic, we first need to examine the structures of acrylic acid and other acrylates. Acrylic acid has the chemical formula of CH2 CHCOOH. So, it is a 3-carbon compound starting with a carboxylic acid and between carbons 2 and 3 is a double bond:
Acrylic Acid Structure
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Acrylic acid is a clear liquid and has a tart scent when it isn't in a polymer form.
Methyl compounds don't like having a double bond, so that double bond will easily react with each other forming a polymer in order to get rid of the double bond on the terminal carbon.
Acrylates are acrylic acid compounds where the hydrogen has been removed on the COOH group and replaced with another group. Acrylates may also have additional substituents on carbons 2 and 3. These acrylates can include:
- Trimethylolpropane Triacrylate (TMPTA)
Types of Polymers
The different compounds are made from the different types of acrylates. For example, we can see the acrylic acid polymer here:
Purple lines indicate the new bonds that formed to bind the acrylic acid compounds together. These bonds originated with the double bonds.
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This chain can keep going on and on until it runs out of acrylic acid compounds to react with. Polymers made from acrylic acid, called polyacrylic acid (PAA), are a super absorbent material and are used in diapers.
Each of the other polymers appears very similar to PAA. For example, methyl methacrylate simply has a different tail, but the polymer still forms at the double bond:
The purple lines indicate the newly formed bonds. The squiggly lines indicate that this polymer continues on in that direction.
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Poly methyl methacrylate (PMAA) is what makes acrylic glass, or Plexiglas. The other acrylates continue this same pattern in forming the polymers.
Poly butyl acrylate (PBA) has seen experiment use in stretchable electronics. Poly ethyl acrylate creates a rubber-like compound. It is also often used alternating with other acrylates to form adhesives. Poly trimethylolpropane triacrylate is used in concrete polymers and setting hardwood floors.
Lesson Summary
Acrylics are compounds with the general structure of acrylic acids or other acrylates. Acrylic products are polymers of these compounds, and a polymer is a long strand of repeating sections. The general structure of acrylic acid is CH2 CHCOOH. Acrylates have a similar structure, with additional groups attached to the carbon atoms and/or replacing the hydrogen on the COOH group.
The polymers form at the double bond, with the rest of the molecule acting as a tail on the polymer. The different types of compounds (such as diapers or Plexiglas) are formed by using the different acrylates in the polymer.
