Interesting Polymer Chemistry Demonstration
The “jumping rubber” polybutadiene reaction is a dramatic chemistry demonstration in which chemicals are reacted and sealed into a container, which pops open, shooting out a polymer “snake”. Here is how to perform the demonstration.
Jumping Rubber Polybutadiene Materials
- Jumping Rubber kit
- plastic or rubber gloves
The Jumping Rubber kit is available sporadically online (search Google) or you can gather the materials yourself:
- alfin catalyst
- 1,3-butadiene in dry pentane
- small bottle with cork for demonstration
Jumping Rubber Procedure
- Put on the gloves. Perform the demonstration in a well-ventilated room, away from heat and flames. Flammable chemicals are involved, so keep a carbon dioxide fire extinguisher available in case of an accident.
- Open the catalyst container and use a glass rod to stir the catalyst into a small bottle of 1,3-butadiene in dry pentane.
- Immediately cork the bottle.
- Shake the bottle and set it down. Be sure that the corked bottle is not pointed toward anyone or anything.
- As the temperature and pressure inside the bottle increase as a result of the polymerization reaction, the cork will pop open and the polymer “snake” will jump out. This occurs within about 2 minutes.
- You can use tongs to handle the polymer and examine it. Note that most of the liquid has been trapped inside the polymer, with very little remaining in the bottle. The pentane in the polymer will evaporate slowly, causing the polymer to shrink.
Safety and Disposal
- Read the safety information accompanying the chemicals. In particular, note that the catalyst and pentane are highly flammable. Avoid inhaling fumes from the chemicals.
- After the pentane has evaporated from the polymer, it is safe to throw it away. The bottle may be rinsed with water and then discarded.
Alfin catalysts consists of a mixture of sodium chloride, allyl sodium and sodium isopropoxide. The catalyst produces rapid polymerization of very high molecular weight polymers based on butadiene, isoprene and other monomers. The molecular weights may be 1-2 million or more.
While most of the polymer is used to make tires for vehicles, it’s also added to other polymers and is used to make golf balls and various elastic materials.
Source: B. Z. Shakhashiri, 1985, Chemical Demonstrations: A Handbook for Teachers of Chemistry, vol. 1, pp. 231-234.