Problem 80 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following are condensation polymers? (1) \(\mathrm{PAN}\) (2) Neoprene (3) polystyrene (4) Poly (ethylene terephthalate) (a) 1 and 4 only (b) 3 and 4 only (c) 2 and 3 only (d) 4 only

Step-by-Step Solution

Answer

The correct answer is (d) 4 only.

Step 1: Understanding Condensation Polymers

Condensation polymers are formed through a condensation reaction, where each step of the process releases a small molecule, often water or methanol, as a byproduct. We need to identify which of the given options are known to form through this type of reaction.

Step 2: Analyzing Option 1: PAN

Polyacrylonitrile (AN]) is a polymer formed from acrylonitrile monomer through addition polymerization, where no small molecule is released in the process. Hence, it is not a condensation polymer.

Step 3: Analyzing Option 2: Neoprene

Neoprene is a synthetic rubber produced through the polymerization of chloroprene. This process is an addition polymerization and does not involve the release of small molecules. Therefore, neoprene is not a condensation polymer.

Step 4: Analyzing Option 3: Polystyrene

Polystyrene is formed from the polymerization of styrene through addition polymerization as well, without any release of small molecules. Thus, it is not classified as a condensation polymer.

Step 5: Analyzing Option 4: Poly (ethylene terephthalate)

Poly (ethylene terephthalate), commonly known as PET, is produced by the reaction between ethylene glycol and terephthalic acid, releasing water as a byproduct. This is a classical example of a condensation polymerization process.

Step 6: Conclusion – Identifying the Correct Answer

From the analysis, only Poly (ethylene terephthalate) fits the criteria of a condensation polymer. Thus, the correct answer involves only this polymer.

Key Concepts

Polymerization

Polymerization is a fundamental chemical process that combines smaller molecules called monomers into a larger, more complex structure known as a polymer. This transformation is crucial in creating a wide variety of materials, including plastics, fibers, and rubbers.
There are several types of polymerization, but they all function on the principle of connecting monomers through chemical bonds. The result is a single chain structure or a three-dimensional network. Understanding polymerization is key to grasping how materials around us are formed and structured, impacting everything from clothing to packaging materials.

Addition Polymerization

Addition polymerization is a type of polymerization where monomers add together without the loss of any small molecules. This process typically occurs with unsaturated monomers containing double bonds, which open up to link with neighboring molecules.
In addition polymerization:

• No byproducts are formed, unlike condensation polymerization.
• The entire monomer molecule becomes part of the polymer chain.
• It is a rapid and straightforward process, often initiated by free radicals.

Example polymers from addition polymerization include polystyrene and neoprene.

Poly (ethylene terephthalate)

Poly (ethylene terephthalate), or PET, is a renowned example of a condensation polymer. It forms from a reaction between ethylene glycol and terephthalic acid, releasing water as a byproduct.
PET features:

• It is widely used in manufacturing beverage bottles and synthetic fibers.
• Exhibits good strength, flexibility, and is recyclable.
• Its production highlights the characteristics of condensation polymerization, where monomers join, eliminating small molecules like water.

Polyacrylonitrile

Polyacrylonitrile (PAN) is a polymer obtained by the polymerization of acrylonitrile through addition polymerization. It is commonly used to produce fibers and is known for high strength and durability.
Key points about PAN:

• It is not a condensation polymer since it forms without releasing small molecules.
• Frequently used in making carbon fiber precursors.
• Its addition polymerization process makes it distinct from polymers like PET that form from condensation reactions.

Neoprene

Neoprene is a synthetic rubber that results from the polymerization of chloroprene. This process involves addition polymerization, where monomers form links without producing water or other byproducts.
Notably, neoprene:

• Is resilient and exhibits outstanding stability across a wide temperature range.
• Is water-resistant and used in products like wetsuits and industrial gaskets.
• Demonstrates how addition polymerization creates robust yet flexible materials.

Polystyrene

Polystyrene is another product of addition polymerization, formed from styrene. It is a versatile polymer with applications ranging from packaging materials to insulation and lightweight protective gear.
Features of polystyrene include:

• It is not a condensation polymer, as no byproducts evolve during its formation.
• Commonly found as expanded polystyrene (EPS), known for its excellent insulative properties.
• Used due to its ease of forming and molding into various shapes, making it important in diverse industries.