Problem 83 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\left[\mathrm{NH}\left(\mathrm{CH}_{2}\right) \mathrm{NHCO}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CO}\right] \mathrm{n}\) is a (a) thermosetting polymer (b) homopolymer (c) co-polymer (d) addition polymer

Step-by-Step Solution

Answer

The polymer is a co-polymer (c).

Step 1: Identify the polymer structure

The given polymer is \( \left[ \mathrm{NH}\left(\mathrm{CH}_{2}\right)_n \mathrm{NHCO}\left(\mathrm{CH}_{2}\right)_4 \mathrm{CO} \right]_n \). This structure represents a long chain made by repeating a specific unit. We need to recognize what kind of polymer this might be by analyzing its repeating unit.

Step 2: Analyze the monomer units in the polymer

The polymer is composed of repeating units that contain different components: \(\mathrm{NH}, \mathrm{CH}_2, \mathrm{NHCO}, \), and \(\mathrm{CO}\left(\mathrm{CH}_{2}\right)_4 \mathrm{CO} \). This suggests the presence of more than one type of monomer in its structure.

Step 3: Understand polymer categorization

Polymers can be classified as homopolymers if they are composed of only one type of monomer unit, and as co-polymers if they are composed of two or more different types of monomer units. Here, the presence of different components such as \(\mathrm{NH}\) and \(\mathrm{CO}\) groups indicates that multiple monomer types are involved.

Step 4: Determine the correct option

Given the analysis from the previous steps, the repeating unit in the polymer is composed of more than one monomer type, specifically involving the functional groups \(\mathrm{NH}\) and \(\mathrm{CO}\). Therefore, this polymer is most accurately classified as a co-polymer because it is formed from two different types of monomers.

Key Concepts

Understanding Thermosetting Polymers

Thermosetting polymers are fascinating materials that undergo a permanent change when heated. These polymers start as viscous liquids but, upon heating, transform into a hardened solid structure due to chemical reactions. This change is irreversible, meaning that once they set, they cannot be remelted. This property makes them ideal for applications that require high thermal stability and structural rigidity.

Some common examples include epoxy resins, phenolic resins, and melamine formaldehyde. Unlike thermoplastics, which can be remelted and reshaped multiple times, thermosetting polymers provide permanent and durable bonds, making them perfect for industrial applications such as adhesives, coatings, and electrical insulations. When considering the polymer in the original exercise, it is crucial to identify if the setting process is irreversible. If so, it could potentially fit the category of thermosetting polymers. However, the distinguishing factor typically lies in the nature of the chemical bonding and the curing process the polymer undergoes during its formation.

Exploring Homopolymers

Homopolymers are a type of polymer consisting completely of identical monomer units linked together. Using only one type of monomer gives homopolymers uniform properties throughout the material, which can be predictable and straightforward to understand and utilize.

Typical examples of homopolymers include polyethylene, which is derived solely from ethylene monomers, and polyvinyl chloride, made entirely of vinyl chloride monomers. Homopolymers are often valued for their simplicity, which allows for targeted application without the complexity that arises from a mixed monomer composition. However, the simplicity might limit functional diversity, which is sometimes crucial in advanced technological applications.

In contrast to the polymer in the original exercise, which has diverse monomer components, homopolymers emphasize the repetitiveness and consistency of a single monomer type, creating uniform structural characteristics.

The Importance of Polymer Categorization

Polymer categorization is essential for understanding their varied applications and properties. Polymers are broadly categorized by the types and arrangements of the monomers that make them up, which affects their behavior and suitability for various uses.

The two primary categories are homopolymers and co-polymers. Homopolymers consist of only one type of monomer, leading to consistent properties throughout the material. Co-polymers, on the other hand, are formed when two or more monomers join together, providing a unique mix of properties from each monomer. This can lead to functionalities that are difficult to achieve with homopolymers alone.

• Thermoplastic vs. Thermosetting: Thermoplastic polymers can be reshaped multiple times upon heating, while thermosetting polymers undergo a chemical change making them harden permanently.
• Biodegradable vs. Non-biodegradable: Some polymers break down in the environment, while others persist, affecting ecological considerations.

When analyzing polymers, such as the example in the exercise, noting whether it contains varied monomers (co-polymer) or uniform monomers (homopolymer) is crucial for determining its categorization and potential applications.

Role of Functional Groups in Polymers

Functional groups are specific groupings of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. When it comes to polymers, these functional groups play a pivotal role in determining the material's properties and functionalities.

Common functional groups found in polymers include hydroxyl groups (OH), amino groups (NH extsubscript{2}), and carboxyl groups (COOH). These groups can impact the polymer’s solubility, melting point, durability, and chemical reactivity. For example, polyesters are known for their durability and elasticity, due to their ester functional groups.

• Amino ( ext{NH extsubscript{2}}) and carboxyl (COOH) groups typically enhance adhesion and bonding capabilities.
• Hydroxyl (OH) groups can increase solubility in water and affect the polymer's flexibility.

In the polymer presented in the original exercise, functional groups like NH and CO play a role in forming stronger connections between chains, affecting the polymer's overall mechanical properties and uses.