Polymers Chapter - Chemistry JEE Main

A substance or a material consisting of very large molecules or macromolecules composed of many repeating subunits is known as polymer. Due to their broad spectrum, both natural and synthetic polymers play essential roles in our everyday life. Polymers belong to the family of synthetic plastic such as polystyrene to natural polymers to natural biopolymers such as protein and DNA that are fundamental to biological structure and function. Polymers synthetic and natural both are created by polymerization of many small molecules named as monomers. Their large molecular mass relative to small molecule compounds produces unique physical properties.

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Polymer term is derived from the Greek word polus meaning many or much and meros meaning parts, and refers to the large molecules whose structure is composed of many repeating units, from which originates a characteristic of higher relative molecules whose structure composes of multiple properties in it. Polymer drive composing this unit actually or conceptually from molecules of low relative molecular mass. In 1833 the term was coined by Jons Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. 

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History

Essential components of commodities are said to be for polymers since the early day for humankind. The use of linen fibers, cotton, wool for garments, paper reeds for paper are just a few examples of how our ancestors exploited polymers containing raw material to obtain artifacts. The cactus trees latex sap reached Europe in the 16th century from South America long after olmec, atzec and maya had started using it as a material to make balls and waterproof textiles and containers. The polymers chemical manipulation dates back to the 19th century although at this time the nature of the species was not understood. The behaviour was initially rationalised by polymers, according to the theory proposed by Thomas Graham which considered them as colloidal aggregates of small molecules held together by the forces which are unknown.

The potential of polymers to provide innovative accessible and cheap materials was grasped immediately. 

Hermann Staudinger in 1920 published his seminal work uber polymerisation in which he proposed that polymers were the long chains of atoms which are linked by covalent bonds. 

Long after many debates his work was also accepted, he was awarded the Nobel prize in 1953.

Polymers entered a golden age after the 1930s during which new types were discovered and quickly given commercial applications. 

Definition: 

Polymers are macromolecules with high molecular weights formed by the repetitive bonding of small units or monomers. These monomers can be the same (homopolymers) or different (copolymers).

Significance: 

Polymers have diverse applications in industries such as packaging, automotive, electronics, medicine, and more. They are cost-effective, lightweight, and offer various mechanical and chemical properties.

Nomenclature

For naming polymer substances the multiple convention is used. Many of the polymers which are used commonly such as those found in consumer products are referred to by a common or trivial name. Based on the historical precedent the trivial name is assigned for popular uses rather than a standardized naming convention. Both the IUPAC and the American chemical society(ACS) have proposed standardized naming conventions. The IUPAC and ACS are similar to each other but are not identical.

The Example of Different Namings by Different Institutions are Given below:

In both the conventions the polymer names are intended to reflect the monomers from which they are synthesised from the simple alkane ethane called polyethylene.

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Properties

Depending on the structure of polymers the property of polymers is determined, and they are divided into classes according to their physical base. Many chemical and physical properties describe how a polymer behaves as a continuous macroscopic material. These are classified as bulk properties according to thermodynamics, intensive properties. Mechanical properties: the polymers bulk properties are those most often of end use internet. These properties are the properties which dictate how the polymer behaves on a microscopic scale. Tensile strength, young’s modulus of elasticity also comes under this.

Transport properties: diffusivity like transport properties are included in this. These are very important in many of the applications crystallization and melting, glass transition, mixing behaviours come under this.

There are many more properties which include chemical properties, electrical properties and optical properties. 

Classification

Polymers can be classified on the  basis of different properties and the properties used to classify them include structure, molecular forces, source, mode of polymerization, and growth polymerization. 

1. Classification on the Basis of Source of Polymer

It is further divided into natural, semi-synthetic, and synthetic polymers. 

1. Natural Polymers: Polymers that are obtained from living organisms such as plants and animals. They are found in living beings and they sustain metabolic activities in plants and animals. Natural polymers form components in bodybuilding and maintenance in both kingdoms. They are ubiquitous and found everywhere. For example, cellulose, rubber, etc.

2. Semi-synthetic Polymers: These are derived from cellulose. The fundamental source of semi-synthetic polymers is natural polymers themselves. But they are modified through an artificial chemical treatment to either enhance or reduce certain properties. This human intervention ensures that a particular natural polymer is now better suited to function in the specific role it was destined for.

Examples: cellulose acetate, rayon, nitrocellulose, etc.

3. Synthetic Polymers: The polymers that are obtained from chemical processes and used in our daily lives are called synthetic polymers. They are derived from petrochemical sources like petroleum and oil. Like semi-synthetic polymers, they undergo treatment in order to build desirable properties like durability and flexibility. Thus they exhibit numerous desirable properties.

Example: Vulcanized rubber, nylon, Teflon, polyethylene, etc.

2. Classification on the Basis of the Structure of A Polymer

It is further classified as Linear polymers, branched chain polymers and cross linked or network polymers.

1. Linear Polymers: These are made by using straight and long chains of monomers. For example, polyester, nylon, teflon, etc.

2. Branched Chain Polymers: These are polymers formed by linear polymers when they divide into different branches. For example, polyethylene, glycogen, starch, etc. 

3. Cross-linked or Network Polymers: These polymers are formed by joining two linear polymers through strong covalent bonds.  For example, fiberglass, adhesives, polyester, etc. 

3. Classification on the Basis of Mode of Polymerization

It is further classified into different types such as addition polymers and condensation polymers. 

1. Additional Polymers: These are formed by repeated attachment of unsaturated monomers irrespective of the bond they possess (double or triple).

2. Condensation Polymers: These are formed by condensation reactions between two different monomers and they result in the removal of small molecules such as water, etc. 

4. Classification on the Basis of Molecular Forces

Polymers are used for different purposes depending on their elasticity, tensile strength, etc. The mechanical forces of polymers are determined by hydrogen bonds, ionic bonds, etc. 

On the basis of intermolecular forces, the polymers can be divided into the following types:

1. Elastomers: Elastomers are solids possessing elastic properties. These polymers have low molecular forces between each monomer which helps monomers to stretch easily. For example, polybutadiene, polyisoprene, etc.

2. Fibers: These are made of thread like structures and have high tensile strength. For example, terylene. 

3. Thermoplastic Polymers: These are  linear or branched chain polymers that become soft on heating and hard when cooled. For example, nylon, acrylic, etc. 

4. Thermosetting Polymers: These are highly branched polymers. When these polymers are heated they cannot be reversed back to the original shape and cannot be reused. For example, erasers, balloons, etc. 

5. Classification on the Basis of Growth Polymerization

Addition and condensation polymers are also known as chain growth polymers.

1. Natural Polymers: Polymers that are obtained from natural things are called natural polymers. They are mainly obtained from plants and animals and human beings. For example, DNA, RNA, glucose, etc. Natural foods are made of natural polymers such as carbohydrates, proteins, etc. The packages in which food is delivered are also made of polymers such as plastic containers, packets, one time use cutlery, etc. 

2. Important Polymers Include: Cellulose, nucleic acids, proteins, carbohydrates, rubber, and chiton. 

3. Cellulose: It is made of long chains of glucose. It is the most natural polymer, found abundantly in plants. They consist of stretched-out fibers, which is a property of cotton plants, allowing them to  become fabric. Cellulose is not dissolved by water and therefore it is used in the manufacturing of paper.

4. Chiton: It is present in the cell wall of parasitic cells. It is found in the external skeleton of crabs, spiders, etc. 

5. Carbohydrates: Polymers formed from glucose. Starch and sugars are a type of carbohydrates which can be  used for energy production by animals and plants. It is known that the Cellulose and carbohydrates are both made of glucose but only the difference is in their structure in which one has  clustered chain and the other has a stretched chain and there is one more  difference that is  carbohydrates are soluble in water and can be easily digested by human beings but cellulose is not digested by human beings because it is not soluble in water.  

6. Proteins: Proteins are made of aminoacids which are organic compounds which contain one carboxylic group, an amine group, and a side chain R which is specific to each amino acid. There are a total of twenty amino acids and two or more amino acids combine together to form different proteins. There are a large number of proteins which are found in feathers, fur, finger/toenails, hair, etc. In animals, wool, silk, and leather are the important fibers that are made of proteins. 

7. DNA and RNA: DNA and RNA are macromolecules and are made of nucleotides. Nucleotides are organic molecules and consist of purines and pyrimidines which are also called nitrogenous bases, ribose sugar in RNA and deoxyribose sugar in DNA and a phosphate group. These polymers are formed due to condensation. 

8. Rubber: Rubber is a polymer of isoprene monomers and it is formed by addition polymerization. It is obtained from latex secreted by rubber trees.

Synthetic Polymers

Synthetic polymers are advantageous as they are very stable. They can also be customized based on the requirements and purpose. 

Example: Plexiglas, styrofoam, nylon, etc.

Synthetic polymers have become a necessity in day to day life. Almost everything that we use is made up of artificial polymers. Being stable is not just an advantage but can be a disadvantage too as it means these polymers cannot be broken down naturally leading to accumulation in the environment resulting in various toxic conditions in the environment. One way to break down or destroy these artificial polymers is by burning them or heating them at very high temperatures but again this is also not an environmental approach as it causes the release of toxic gasses.

Copolymerisation

A variety of monomers react to undergo polymerization to form polymers known as copolymers.

Example: Acrylonitrile - styrene copolymer

Biodegradable Polymers

A large number of polymers due to their strong links are very hard to break and therefore degrade. This causes them to accumulate in the surrounding environment and become toxic and cause an imbalance in nature. To avoid such situations recently new varieties of artificial polymers are being manufactured which can easily be degraded and hence are as much toxic.

Awareness must be spread continuously to avoid the use of non-biodegradable polymers and to use biodegradable materials.

Natural and Synthetic Rubber

Natural Rubber:

Natural rubber is one of the earliest and most versatile polymers known to humankind. It has been used for centuries by indigenous cultures for various purposes, but its wide-scale use took off in the 19th century with the development of the rubber industry.

Source:

Natural rubber is derived from the latex of the Hevea brasiliensis tree, commonly known as the rubber tree.

The latex is collected by tapping the tree's bark, and it contains rubber particles suspended in an aqueous solution.

Polymer Structure:

The primary polymer in natural rubber is polyisoprene, a hydrocarbon consisting of a repeating unit of isoprene (C5H8).

The polymer chain of polyisoprene is highly flexible, making natural rubber an elastic material.

Properties:

Elasticity: Natural rubber is highly elastic, meaning it can be stretched and returns to its original shape when the stress is released. This property makes it ideal for various applications where flexibility is required.

Tensile Strength: It exhibits excellent tensile strength, allowing it to withstand mechanical stresses.

Abrasion Resistance: Natural rubber is resistant to abrasion and wear, which is advantageous in applications like tires.

Low Temperature Flexibility: It remains flexible at low temperatures, making it suitable for cold weather applications.

Applications:

Natural rubber is used in a wide range of applications, including:

Tires: It is a crucial component of vehicle tires, providing grip and shock absorption.

Rubber Bands: Its elasticity is ideal for holding objects together.

Footwear: Rubber soles in shoes and boots offer comfort and durability.

Industrial Products: It is used for gaskets, seals, conveyor belts, and hoses.

Natural rubber is valued for its unique combination of properties, making it indispensable in various industries. Its elasticity and durability are particularly important in applications where flexibility and resilience are required, such as tires and industrial seals.

Synthetic Rubber:

While natural rubber has several advantages, synthetic rubber has gained prominence for its versatility and adaptability to specific applications. It is chemically synthesized from petrochemical sources and offers a broader range of properties.

Sources:

Synthetic rubbers are derived from petrochemical sources, primarily through polymerization processes.

Common examples of synthetic rubber include:

Styrene-Butadiene Rubber (SBR)

Polybutadiene Rubber (PBR)

Neoprene

Nitrile Rubber (NBR)

Ethylene Propylene Diene Monomer (EPDM)

Properties:

Synthetic rubbers vary in their properties, depending on their composition and the specific monomers used in their synthesis.

They offer flexibility, resistance to wear and tear, and the ability to withstand exposure to various environmental factors.

Synthetic rubber is used in applications that require specific properties not easily achievable with natural rubber.

Vulcanization:

Vulcanization is a critical process that enhances the properties of rubber, whether natural or synthetic, by cross-linking the polymer chains with sulfur. This process was discovered by Charles Goodyear in the mid-19th century and revolutionized the rubber industry.

Definition:

Vulcanization is a chemical process that introduces cross-links between the polymer chains of rubber.

The cross-linking process involves the addition of sulfur to the rubber, which forms bridges between the polymer chains.

Importance:

Vulcanized rubber exhibits several key improvements, such as:

Enhanced Durability: Vulcanized rubber is more durable and resistant to wear and tear.

Increased Heat Resistance: It can withstand higher temperatures without deforming.

Resistance to Chemicals: Vulcanized rubber is less susceptible to damage from chemicals.

Improved Elasticity: It retains its elasticity while offering better mechanical properties.

Applications:

Vulcanized rubber is widely used in the manufacturing of:

Automobile Tires: The durability and heat resistance of vulcanized rubber make it an ideal choice for tires.

Conveyor Belts: Vulcanized rubber provides the required toughness for conveyor systems.

Shoe Soles: It enhances the lifespan and performance of footwear.

Industrial Products: Vulcanization is essential in creating gaskets, seals, and hoses.

Vulcanization is a critical step in the rubber industry, enhancing the utility and longevity of rubber products. It has transformed the way rubber is used in various applications, particularly in the automotive industry, where durable tires are essential.

Important Polymers:

Several polymers have played a significant role in modern industrial applications and have become part of our daily lives. Let's explore some essential polymers, along with their monomers and uses:

Polyethylene (PE):

Monomer: Ethylene (C2H4)

Types: Polyethylene is broadly categorized into two main types:

High-Density Polyethylene (HDPE)

Low-Density Polyethylene (LDPE)

Properties: PE is known for its low cost, chemical resistance, and easy processability. It is lightweight and possesses good electrical insulating properties.

Uses:

HDPE: Used for making bottles, pipes, and containers. It is suitable for applications where high chemical resistance is required.

LDPE: Commonly used for making plastic bags, films, and various packaging materials.

Polyethylene is one of the most widely used polymers globally due to its affordability and versatility.

Nylon:

Monomers: The composition of nylon can vary depending on the type, but common monomers include adipic acid and hexamethylene diamine.

Properties: Nylon is known for its high tensile strength, durability, and resistance to abrasion. It also exhibits excellent thermal properties and can be molded into various forms.

Uses:

Textiles: Nylon is used in the production of clothing, such as nylon stockings and activewear. It is prized for its strength and elasticity.

Engineering Plastics: It is employed in the manufacture of gears, bearings, and other mechanical components.

Industrial Applications: Nylon is used in various industrial settings, such as conveyor belts and ropes.

Nylon is highly versatile and has a wide range of applications in industries such as textiles and engineering.

Polyester:

Monomers: The primary monomers used in polyester synthesis are terephthalic acid and ethylene glycol.

Properties: Polyester is appreciated for its excellent resistance to water, chemicals, and abrasion. It is durable and can be easily dyed.

Uses:

Textiles: Polyester is a common material for clothing, including polyester fabric. It is also used in upholstery and home furnishings.

PET Bottles: It is used to make PET bottles commonly used for beverages and other liquids.

Films and Sheets: Polyester is employed in the production of films and sheets for various applications, including packaging.

Polyester is a versatile polymer with applications in the textile and packaging industries, thanks to its desirable properties.

Bakelite:

Monomers: Bakelite is synthesized from phenol and formaldehyde.

Type: Bakelite is a thermosetting plastic, meaning it sets permanently when heated and cannot be melted or reshaped.

Properties: Bakelite is heat-resistant, durable, and an excellent electrical insulator. It is known for its ability to hold its shape and structure even under high temperatures.

Uses: 

Bakelite has been historically used for:

Electrical Switches: It is ideal for making electrical switches and components due to its heat resistance and insulating properties.

Radio and Telephone Casings: Early radios and telephones often featured bakelite casings.

Decorative Objects: Bakelite has been used in the creation of various decorative objects and jewelry.

Bakelite was one of the earliest plastics and played a significant role in the development of the plastics industry. Its properties made it invaluable in electrical and electronic applications.

Applications

Synthetic polymers are nowadays used in almost all walks of life. Modern society would look very different from them. The polymer spreading use is connected to their unique properties low cost, low density, good thermal/electrical insulation, high resistance to corrosion, low energy demanding polymer manufacture and facile processing into the final product. 

The properties for a given application of polymer can be turned or enhanced by combination with other materials as in the composites. Polymers application allows to save energy, protect food and drinking water, save land and reduce the use of fertilizers, preserve other materials and protect lives. 

Accessories, clothing, sports wear: PVC clothing and polyester, spandex and sports shoes, footballs west, billiards ball, skis and snowboards, rackets etc. 

Electronic and photonic technologies, containers and packaging, car parts, security, money, separation technologies.

Natural Polymers Structure Characteristics and Uses

Natural polymers, derived from biological sources, exhibit distinctive structures, properties, and versatile applications across various fields. This table encapsulates the essence of various 5 natural polymers structure characteristics and uses. From cellulose fortifying plant cell walls to the indispensable role of DNA in genetics, these polymers epitomize nature's ingenuity and serve as pivotal elements in both natural processes and human innovation.

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Conclusion

The chapter on Polymers in JEE Main is an essential exploration of the fascinating world of macromolecules. Polymers, which are large, chain-like molecules made up of repeating units, play a vital role in our daily lives. They are ubiquitous, found in everything from plastics and textiles to pharmaceuticals and biomolecules. This chapter delves into the classification of polymers, the methods of polymerization, and the diverse properties and applications of various polymers, such as polyethylene, nylon, polyester, and Bakelite. Additionally, the significance of vulcanization in enhancing the properties of rubber, whether natural or synthetic, is discussed.