Class 12 Chemistry Chapter 15 Notes Polymers

Class 12 Chemistry contains topics that help students learn new concepts and ideas  and create a strong foundational base for higher studies. Chapter 15 of the CBSE Chemistry Class 12 Syllabus is Polymers. In this topic, you will study what polymers are and how they are synthesised. Students will also study how polymers are being used nowadays. To make this topic easier for students, they need to refer to  Class 12 Chemistry Chapter 15 Notes.

These  notes are prepared by Chemistry faculty experts  appointed by the Extramarks in a  systematic and organised way so the students can easily understand the new topics and quickly solve the questions in the exercise and examinations. You can access these Class 12 Chemistry Chapter 15 Notes on polymers and  study the chapter at your own convenience. It makes your study schedule more flexible and  easier to comprehend.

Key Topics Covered in Class 12 Chemistry Chapter 15 Notes 

The word ‘polymer’ is derived from two Greek words, where ‘Poly’ means ‘Many’, and ‘Mer’ means ‘Unit’ or ‘Part’. A polymer is a high molecular mass molecule made up of a large number of one or more different types of components with small molecular weight. 

Monomer refers to the small unit(s) from which polymer is formed. A chemical combining several similar or distinct molecules to produce a single big molecule is known as polymerisation. Polymers have huge applications everywhere. 

For example, hot water bags, toothbrushes, switches, and ropes are all polymers.

A polymer made up of one monomer molecule is called Homopolymer. Examples are Polyethene, PVC, PAN, Teflon, Buna rubber, and other materials.

Plastics or polymers are an integral part of our daily life. A copolymer is a polymer of more than one type of monomer. Nylon-6,6, Buna-S, Dacron,  Bakelite, and so forth.

Polymers may naturally occur in plants and animals (natural polymers) or artificial (synthetic polymers). Different polymers have unique physical and chemical properties.

Polymers cannot be classified under one category due to their complex structures, different behaviours and broad applications. We can, therefore, classify polymers depending on the following considerations.

Classification of Polymers depends on the Source of Availability:

There are three types of polymers under this category: 

• Natural
• Synthetic
• Semi-synthetic.

1. Natural Polymers:

They occur naturally and are found in animals and plants. For Example, starch, proteins,  cellulose, and rubber. 

2. Semi-synthetic Polymers:

They are found from naturally occurring polymers and undergo further chemical changes. For Example, cellulose nitrate and cellulose acetate.

3. Synthetic Polymers:

These are artificial polymers. Plastic is the most common and vastly used synthetic polymer. It is used in industries and several dairy products. For Example, nylon-6, 6, polyether etc. 

Students may refer to NCERT Class 12 Chemistry Chapter 15 Notes for a more detailed explanation of the above Polymers.

Classification of Polymers depends on the Structure of the Monomer Chain:

This category has the following Classifications:

1. Linear Polymers:

The structure of polymers consists of long and straight chains that fall into this category. PVC, i.e. polyvinyl chloride, is used mainly for making pipes and electric cables and is an example of a linear polymer.

2. Branched-chain Polymers:

When a polymer’s linear chains have some branches, such polymers are categorised as branched-chain polymers. Low-density polythene is an Example of a branched-chain polymer.

3. Cross-linked Polymers:

Bifunctional and trifunctional monomers arrange them. These polymers have a stronger covalent bond than other linear polymer chains. 

Other Ways to Classify Polymers:

Classification Based on mode of polymerisation:

Addition Polymerisation: 

The repeated addition of monomer molecules forms these polymers. The polymer is formed by the polymerisation of monomers with double or triple bonds (unsaturated compounds). There is no elimination of tiny molecules like water or alcohol in this process (no by-product of the process). In addition, polymers always have their empirical  formulas the same as their monomers. Examples are ethene n(CH2=CH2) to Polyethene -(CH2-CH2)n-, Teflon, and Polyvinyl chloride (PVC).

Free Radical Mechanism: 

Students will learn more about the free radical mechanism  in  Class 12 Chemistry Chapter 15 Notes. Many alkenes or dienes and their derivatives are polymerised in the presence of a free radical (catalyst) like benzoyl peroxide. The sequence of steps may be shown as follows:

• Chain initiation steps
• Chain propagation step
• Chain terminating step:

1. The polymerisation of ethene to polythene consists of heating or exposing a mixture of  ethene with a tiny amount of benzoyl peroxide initiator to light. The process initiates with adding phenyl free radical formed by the peroxide to the Ethene double bond, generating a new and more significant free radical. This step is termed as the chain initiating step.
2. As this radical interacts with another molecule of Ethene, another bigger-sized radical is formed. The continuation of this sequence with new and more significant radicals carries the reaction forward, and the step is termed a chain propagation step.
3. Ultimately, at a few stages, the product radical thus formed reacts with another radical to form the polymerised product. This step is called the chain-terminating step.

Chain terminating step

Preparation of some Important Addition Polymer Reaction:

1. Polythene: 

There are two types of polythene:

1. Low-density polythene: 

The polymerisation of Ethene acquires it under high pressure of 1000- 2000 atmospheres and at a temperature of 350 K-570 K in the presence of traces of dioxygen or a peroxide initiator (catalyst). The low-density polythene (LDP) obtained through the free radical addition, and H-atom abstraction has a highly branched structure. 

Low-density polythene is chemically inert and rigid but flexible and a poor conductor of electricity. Hence, it is used to insulate electricity carrying wires and manufacture squeeze bottles, toys and flexible pipes.

1. High-density polythene: 

It is formed if the addition polymerisation of Ethene takes place in a hydrocarbon solvent in the presence of a catalyst such as triethyl aluminium and titanium tetrachloride at a temperature of 333 K to 343 K and under pressure of 6-7 atmospheres.

High-density polythene (HDP), thus produced, consists of linear molecules and has a high density because of close packing. It is also chemically inert and more complex and rigid. It is utilised for manufacturing buckets, dustbins, bottles, pipes, etc.

2. Polytetrafluroethene (Teflon):

Teflon is synthesised by heating tetrafluoroethene with a free radical or per sulphate catalyst at maximum pressures. It is a chemically inert and corrosive reagent. It is utilised in making oil seals and gaskets and for non–stick surface coated utensils.

3. Polyacrylonitrile:

The addition polymerisation of acrylonitrile in the presence of a peroxide catalyst leads to the formation of polyacrylonitrile. It is applied as a substitute for wool to make commercial fibres such as Orlon or Acrilan.

Extramarks Class 12 Chemistry Chapter 15 Notes and study material is accessible on the Extramarks website for students who want to learn more about the Polythenes mentioned above.

Condensation Polymerisation or step-growth polymerisation:

This type of polymerisation consists of a repetitive condensation reaction between two bi-functional monomers. These polycondensation reactions result in the loss of some simple molecules such as water, alcohol, etc., and lead to the formation of high molecular weight condensation polymers. In these reactions, the product of every step is again a bi-functional species, and the sequence of condensation goes on. Hence each step produces a distinct functionalised species and is independent of each other. 

This process is called step-growth polymerisation. The development of Terylene or Dacron by the interaction of ethylene glycol and terephthalic acid is an Example of this type of polymerisation.

A typical Example is the polymerisation of HExamethylenediamine and adipic acid. To give Nylon – 66, where water molecules are eliminated. For Example, Nylon -6, 6, perylene, and polyester.

Some important condensation polymerisation reactions characterised by their linking units are described below:

Preparation of Important Condensation Reaction:

1. Polyamides:

These polymers possessing amide linkages are actual Examples of synthetic fibres and are termed nylons. The general preparation method consists of the condensation polymerisation of diamines with dicarboxylic acids and amino acids and their lactams.

Preparation of Nylons:

1. Nylon 6 6:

Students will learn about nylon 6 6 under this section of Class 12 Chemistry Chapter 15 Notes. The condensation polymerisation of Hexamethylenediamine prepares it with adipic acid under high pressure and at high temperatures. Nylon 6 6 is used in making bristles for brushes, sheets and in the textile industries.

1. Nylon 6: 

It is formed by heating Caprolactam with water at a high temperature.

Nylon 6 is used to manufacture tyre cords, fabrics and ropes. 

2. Polyesters: 

These are the polycondensation products of dicarboxylic acids and diols. Dacron or Terylene is the best-known Example of polyesters. It is developed by heating a mixture of ethylene glycol and terephthalic acid at 420 to 460 K in the presence of Zinc acetate antimony trioxide catalyst. Dacron fibre (Terylene) is crease-resistant and is utilised in blending with cotton and wool fibres, as glass reinforcing materials in safety helmets, etc.

3. Phenol–formaldehyde polymer (Bakelite and related polymers): 

Phenol-formaldehyde polymers are the oldest synthetic polymers. These are formed by the condensation reaction of phenol with formaldehyde in the presence of either an acid or a base catalyst. The reaction initiates with the initial formation of o-and/or p-hydroxymethyl phenol derivatives, which further react with phenol to form compounds having rings joined to each other through the –CH2 group. The initial product could be linear – Novolac used in paints.

Novolac, on heating with formaldehyde, undergoes cross-linking to form an infusible solid mass called Bakelite. It is used for making combs, phonograph records, electrical switches and handles of various utensils.

4. Melamine- formaldehyde Polymer: 

Melamine formaldehyde polymer is created by the condensation polymerisation of melamine and formaldehyde. It is applied in the manufacture of unbreakable crockery. 

Students may refer to NCERT Class 12 Chemistry Chapter 15 Notes for a more detailed explanation of this polymerisation.

The Classification depends on monomers:

• Homopolymer: 

In Homopolymer, a single type of monomer unit is present. For Example, Polyethene.

• Heteropolymer or copolymer: 

It consists of different types of monomer units. For Example, nylon -6, 6.

Students may refer to Extramarks NCERT Solutions in addition to Class 12 Chemistry Chapter 15 Notes for a more detailed explanation of the monomers and their types.

Classification Based on Molecular Forces:

• Elastomers:

These are rubber-like solids with elastic properties where weak binding forces are present. Examples are Rubber, Buna -S, buna-N, and neoprene.

• Fibres: 

Strong, rigid, high tensile strength and strong interaction forces are present. For Example, nylon -6, 6, polyesters(terylene).

• Thermoplastics: 

These have intermediate forces of attraction. Examples are polyvinyl chloride and polystyrene.

• Thermosetting polymers: 

These polymers significantly improve the material’s mechanical properties. It provides enhanced chemical and heat resistance. These cannot be reused. Examples are phenolics, epoxies, and silicones.

Structure of Polymers:

Some of the polymers around us are made up of a hydrocarbon backbone. A hydrocarbon backbone is a large chain of linked carbon and hydrogen atoms, possible because of the tetravalent nature of carbon.

Some Examples of a hydrocarbon backbone polymer are polypropylene, polybutylene, and polystyrene. So, there are polymers which, instead of carbon, have different elements in their backbone. For Example, Nylon contains nitrogen atoms in the repeated unit backbone.

Types of Polymers:

Depending on the type of the backbone chain, polymers can be categorised into:

• Organic Polymers: Carbon backbone.
• Inorganic Polymers: Backbone constituted by elements other than carbon.

Biodegradable Polymers:

The polymers degraded and decayed by microorganisms like bacteria are known as biodegradable polymers. These polymers are used in surgical bandages, capsule coatings and surgery. For Example, Poly hydroxybutyrate co vel [PHBV]

High-Temperature Polymers:

These polymers are stable at high temperatures. Due to their high molecular mass, these do not vanish even at very high temperatures. They are extensively utilised in the healthcare industries for making sterilisation equipment and manufacturing heat and shock-resistant objects.

A few of the essential polymers are:

1. Polypropylene:

It is a polymer that softens beyond a specific temperature, allowing it to be moulded. It solidifies on cooling. Because of its ability to be easily moulded into several shapes, it has a lot of applications.

A few are in stationary equipment, automotive components, reusable container speakers and much more. Because of its relatively low energy surface, the polymer is connected to the welding process, which does not require glue.

2. Polyethene:

It is the most common plastic around us and is primarily used in packaging, from plastic bags to plastic bottles. There are various types of  polyethene, but their standard Formula is (C2H4)n.

Properties of Polymers:

Physical Properties:

• As chain length and cross-linking increase, the tensile strength of the polymer increases.
• Polymers do not melt and change states from crystalline to semi-crystalline states.

Chemical Properties:

• Compared to conventional molecules with various side molecules, the polymer is enabled by hydrogen and ionic bonding resulting in better cross-linking strength.
• Dipole-dipole interaction bonding side chains enable the polymer for maximum flexibility.
• Polymers with van der Waal forces linking chains are known to be weak but give the polymer a low melting point.

Optical Properties:

• Due to their changing their refractive index with temperature, as in the case of PMMA & HEMA: MMA, they are utilised in lasers for spectroscopy and analytical applications.

Some Polymers and their Monomers:

• Polypropene, also termed polypropylene, is made up of monomer propene.
• Polystyrene is aromatic; naturally, a transparent polymer made up of styrene monomer.
• PVC( Polyvinyl chloride) is a plastic polymer prepared with monomer vinyl chloride.
• Generally, the urea-formaldehyde resin is a translucent plastic obtained by heating formaldehyde and urea molecules.
• Glyptal is formed of monomers ethylene glycol with phthalic acid.
• Bakelite or polyoxybenzylmethylenglycolanhydride is a plastic made up of monomers phenol and aldehyde.

Copolymerisation:

In this process, two different monomers join to form a polymer. This polymerisation prepares synthetic rubbers. For Example, BUNA – S.

Copolymerisation is a reaction in which a mixture of more than one monomer species is allowed to polymerise to obtain a polymer. The copolymer can be formed not only by chain growth polymerisation but by step-growth polymerisation also. It consists of multiple units of each monomer used in the same polymeric chain. 

For Example, a mixture of 1, 3–butadiene and styrene can form a copolymer. 

Copolymers have properties quite different from homopolymers. For Example, the butadiene-styrene copolymer is quite tough and is a good substitute for natural rubber.

It is used to manufacture auto tyres, floor tiles, footwear components, cable insulation, etc.

Rubber:

Rubber is a natural polymer and consists of elastic properties. It is also termed an elastomer and has a variety of practical applications. It is manufactured from rubber latex, colloidal dispersion of rubber in water. This latex is formed from the bark of rubber trees and is found in India, Sri Lanka, Indonesia, Malaysia and South America.

1. Natural Rubber: 

Natural rubber may be considered a linear polymer of isoprene (2-methyl-1, 3-butadiene) and is also called cis – 1, 4 -polyisoprene. The cis-polyisoprene molecule consists of several chains held together by weak van der Waals interactions and has spiral structures.

Therefore, it can be stretched like a spring and exhibits elastic properties.

Vulcanisation of Rubber:

Natural rubber usually becomes soft at high temperatures (>335 K) and brittle at low temperatures (<283 K) and shows high water absorption capacity. It is dissolved in non-polar solvents and is non-resistant to attack by oxidising agents. A vulcanisation process is carried out to improve upon these physical properties. This process involves heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range of 373 K-415 K. 

On vulcanisation, sulphur forms cross-links at the reactive sites of double bonds and hence, the rubber gets stiffened. In the manufacture of rubber tyre 5% of sulphur is used as a cross-linking agent. 

The possible structures of vulcanised rubber molecules are shown below:

2. Synthetic Rubber: 

Synthetic rubber is any vulcanise rubber-like polymer capable of getting stretched twice its length. Though, it returns to its original shape and size as soon as the external stretching force is released. Hence, synthetic rubbers are commonly either homopolymers of 1, 3 – butadiene derivatives or copolymers of 1, 3 – butadiene. It can also be its derivatives with another unsaturated monomer.

Preparation of Synthetic Rubbers:

1. Neoprene: 

The free radical polymerisation of chloroprene obtains neoprene or polychloroprene. It resists vegetable and mineral oils. It is utilised for manufacturing conveyor belts, gaskets and hoses.

1. Buna –N:

It is synthesised by the copolymerisation of 1, 3 – butadiene with acrylonitrile in the existence of a peroxide catalyst. It resists the action of petrol, lubricating oil & organic solvents. It is used in creating oil seals, tank lining, etc.

Apart from Class 12 Chemistry Chapter 15 Notes, students may also refer to other study materials while preparing for the Board or competitive Examination.

Calculate Molecular Mass of Polymers:

Average molecular masses of Polymers can be Classified as below:

• Number Average Molecular Masses.
• Weight Average Molecular Mass.

Students may refer to NCERT Class 12 Chemistry Chapter 15 Notes for a more detailed explanation of the above terms.

Biodegradable Polymers:

As per Class 12 Chemistry Chapter 15 Notes, Many polymers are resistant to environmental degradation and are thus responsible for accumulating polymeric solid waste materials. Aliphatic polyesters are one of the essential Classes of biodegradable polymers. 

 Some of the following  are  noteworthy  examples:

1. Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV): 

This polymer is created by the copolymerisation of 3-hydroxybutyric acid and 3 – Hydroxypentanoic acid. PHBV is used in packaging, orthopaedic devices and controlled release of drugs. PHBV undergoes bacterial degradation in the environment.

2. Nylon 2- nylon 6:

It is an alternating polyamide copolymerisation of glycine (H2N−CH2−COOH) and aminocaproic acid (H2N−(CH2)5−COOH) and is biodegradable.

3. Polyhydroxy butyrate (PHB):

It is formed by condensing hydroxybutyric acid (3-hydroxy butanoic acid) molecules. 

Students can  refer to NCERT Class 12 Chemistry Chapter 15 Notes to learn more about Biodegradable Polymers.

Uses of Polymers:

Here we will summarise a list of the actual uses of polymers in our daily life.

• Polypropene finds usage in a wide range of industries such as textiles, packaging, stationery, plastics, aircraft, construction, rope, toys, pipes, fibres, etc.
• The effective use of polyvinyl chloride(PVC) is the production of sewage pipes. It is most commonly used as an insulator in the electric cables, manufacture of raincoats, handbags, vinyl flooring, and water pipes.
• Polyvinyl chloride is applied in furniture and clothing, which has recently become famous for constructing doors and windows. It is also used in vinyl flooring.
• Polystyrene is the most common plastic in the packaging industry. Bottles, toys, containers, trays, disposable glasses and plates, wrapping materials, radio and television cabinets and lids are some of the daily-used products made up of polystyrene. It is also used as an insulator.
• Urea-formaldehyde resins make adhesives, moulds, laminated sheets, unbreakable containers, etc.
• Glyptal is used for making paints, coatings, and lacquers.
• Bakelite is used for producing combs, electrical switches, kitchen products, handles of utensils, toys, jewellery, firearms, insulators, computer discs, etc.

 Students may visit the Extramarks website to learn more about polymers, biopolymers and other interesting Chemistry topics covered under Class 12 Chemistry Chapter 15.

Class 12 Chemistry Chapter 15: Exercises &  Solutions

The solutions provided in this section help you understand how to answer important  questions appropriately and accurately to ensure that you write all the aspects of any question accurately.

Some of the essential exercise questions and answers for Class 12 Chemistry Chapter 15 include polymers, preparation and uses of polymers etc. The exercise and answer solutions provided by Extramarks are detailed in nature to ensure conceptual clarity in their   learning process. 

The coursework prepared by the Extramarks is precise enough for the students to face questions of any difficulty level during board examinations and various competitive examinations. 

Students can visit the links provided below to access the solutions:

• Class 12 Chemistry Chapter 15: Exercise 15.1 – 15.20 – Questions & Answers

Students can refer to the respective exercise stacked under NCERT Class 12 Chemistry Chapter 15 Notes. Students can also explore all types of educational content on the Extramarks website. 

Click on the respective links below to know more. 

• NCERT Solutions Class 1
• NCERT Solutions Class 2
• NCERT Solutions Class 3
• NCERT Solutions Class 4
• NCERT Solutions Class 5
• NCERT Solutions Class 6
• NCERT Solutions Class 7
• NCERT Solutions Class 8
• NCERT Solutions Class 9
• NCERT Solutions Class 10
• NCERT Solutions Class 11
• NCERT Solutions Class 12

Every  detail a student may need to understand Polymers in Class 12 Chemistry Chapter 15 is clearly described in the notes.

The Class 12 Chemistry Chapter 15 Notes on polymers add to students’ learning skills and test their information recall, comprehension, analytical thinking, and problem-solving ability. It is the most comprehensive study material students can rely on to study, practice various questions, and prepare for board and other entrance Examinations. Students may learn effortlessly once they follow the systematic approach and regular practice to master the topic. 

NCERT Exemplar Class 12 Chemistry

The NCERT Class 12 Chemistry Exemplars are offered here to help students succeed in their CBSE Class 12 and graduate entrance Examinations. NCERT Exemplar for Class 12 Chemistry contains solved chapter-by-chapter questions to assist students in completing a rapid review of the entire syllabus.

Given  below  is the list of study materials students can refer to:

• NCERT Solutions
• CBSE Syllabus
• Important Formulas
• CBSE Extra Questions
• CBSE Revision Notes
• CBSE Notes
• Important Questions
• CBSE Previous Year Question Papers
• CBSE Sample Papers

Students can learn more about the subject by practising problems from this guide. Extramarks’ subject experts conscientiously and diligently prepare answers that  students trust and rely on to pass the board exams with flying colours. 

Key Features of NCERT Solutions Class 12 Chemistry Chapter 15 Notes

Polymer is an essential topic for Examinations like IIT, JEE and NEET. Hence, while studying Chemistry, the best quality Notes and solutions provided by Extramarks prove useful  for students in many ways. 

Class 12 Chemistry Chapter 15 Notes created by the Extramarks has  the following advantages:

• Educated and experienced subject matter experts these notes while strictly adhering to the CBSE guidelines. 
• These critical notes include a detailed explanation of every topic in the chapter. 
• They can be used to study right after school or as revision  notes during Examinations. 
• The Class 12 Chemistry Chapter 15 Notes are helpful for all types of  boards and various competitive Examinations.