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 12 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

The structure of poly(lauryl methacrylate), a long hydrocarbon chain, makes it soluble in oil and allows it to coil into balls at low temperatures, where it has little effect on oil viscosity. However, at high temperatures, the polymer uncoils and forms long chains that interact with the oil's hydrocarbon chains, increasing the resistance to flow and maintaining viscosity. This helps the motor oil remain effective at lubricating and protecting the engine, even at high temperatures.

Step-by-step solution

Understanding the structure of poly(lauryl methacrylate)

Poly(lauryl methacrylate) is a polymer with a long hydrocarbon chain. This structure makes the polymer soluble in oil, which is also composed of hydrocarbons with mostly 12 or more carbon atoms.

Behavior of poly(lauryl methacrylate) at low temperatures

At low temperatures, the polymer chains of poly(lauryl methacrylate) coil themselves into balls. In this state, the polymer chains are not interacting significantly with the oil, so they do not have a substantial effect on the viscosity of the oil.

Behavior of poly(lauryl methacrylate) at high temperatures

As the temperature increases, the coiled polymer balls uncoil and form long chains. These long chains can interact with the hydrocarbon chains present in motor oil. Their interactions can help increase the resistance to flow, thereby maintaining the viscosity of oil at high temperatures.

The effect on viscosity

Without the poly(lauryl methacrylate) additive, the viscosity of motor oil could decrease significantly at high temperatures. This would make the oil less effective at lubricating and protecting the engine. The addition of poly(lauryl methacrylate) helps control the viscosity of motor oil, ensuring that, even at high temperatures, the oil remains effective in performing its intended function.