Question

Poly (lauryl methacrylate) is used as an additive in motor oils to counter the loss of viscosity at high temperature. The structure is

The long hydrocarbon chain of poly(lauryl methacrylate) makes the polymer soluble in oil (a mixture of hydrocarbons with mostly twelve or more carbon atoms). At low temperatures the polymer is coiled into balls. At higher temperatures the balls uncoil and the polymer exists as long chains. Explain how this helps control the viscosity of oil

Short answer

Poly (lauryl methacrylate) polymer has long chains which will interfere with oil chains at higher temperature to increase viscosity.

Step-by-step solution

To explain control the viscosity of oil

Oil viscosity decreases with temperature increase. As a result, at higher temperature motor oil should compensate for viscosity loss. Using lauryl methacrylate polymer, viscosity loss is reduced as the long chains interfere with the oil chains. Basically, chains are mutually intertwined.

Now if the temperature is low, lauryl methacrylate polymer is coiled into a ball. This results in reducing viscosity. Oil viscosity will be optimal and there will not be any additional viscosity gain.

Hence Poly (lauryl methacrylate) polymer has long chains that will at higher temperature interfere with oil chains to increase viscosity