Polymers are large molecules made up of repeating structural units connected by chemical bonds. They are formed by the chemical combination of many small molecules, known as monomers.

A polymer is a large molecule or a macromolecule which essentially is a combination of many subunits. The term polymer in Greek means ‘many parts’. Polymers can be found all around us, from the strand of our DNA, a naturally occurring biopolymer, to polypropylene, which is used throughout the world as plastic.

Polymers can be divided into two categories: natural polymers, which are found in plants and animals, and synthetic polymers, which are man-made. These polymers have a variety of unique physical and chemical properties, making them useful in many aspects of everyday life.

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Table of Contents

Classification of Polymers

Structure of Polymers

Types of Polymers

Properties of Polymers

Some Polymers and their Monomers

Types of Polymerisation Reactions

How to Calculate Molecular Mass of Polymers?

Uses of Polymers

FAQs on Polymers

The process of polymerization is used to create polymers, which are formed when their constituent elements, known as monomers, are reacted together to create polymer chains - three-dimensional networks of polymer bonds.

The type of polymerization mechanism used depends on the type of functional groups attached to the reactants. In the biological context, most macromolecules are either fully polymeric or composed of large polymeric chains.

Classification of Polymers

We can classify polymers based on their complex structures, different behaviours and vast applications. Therefore, it is not possible to classify polymers under one single category.

Sources of Availability for Polymers and Their Classification

There are three categories of classification under this category:

1. Natural Polymers
2. Synthetic Polymers
3. Semi-synthetic Polymers

Natural Polymers:

Plants and animals contain naturally occurring molecules such as proteins, starch, cellulose, and rubber. Additionally, biodegradable polymers, known as biopolymers, can also be found.

Semi-Synthetic Polymers:

Semi-synthetic polymers are materials that are created by combining synthetic and natural components. These materials have properties that are distinct from those of the individual components.

Cellulose nitrate and cellulose acetate are examples of polymers that have undergone further chemical modification from their naturally occurring state.

Synthetic Polymers:

Synthetic polymers are materials composed of long, repeating chains of molecules that are artificially created.

These are man-made polymers. The most commonly used and widely available synthetic polymer is plastic. It is utilized in industries and for various dairy products, such as nylon-6, 6, and polyethers.

Check Out: Natural Polymers vs Synthetic Polymers

Classification of Polymers Based on the Structure of the Monomer Chain

This category has the following classifications:

Linear Polymers

The structure of polymers containing long and straight chains falls into this category. PVC, i.e. poly-vinyl chloride, which is largely used for making pipes and electric cables, is an example of a linear polymer.

Branched-Chain Polymers

Branched chain polymers are polymers in which linear chains form branches. For example, Low-density polythene.

Cross-linked Polymers

Polymers composed of bifunctional and trifunctional monomers have a stronger covalent bond than other linear polymers. Examples of this type of polymer include Bakelite and melamine.

Other Ways to Classify Polymers

Classification Based on Polymerization

Addition Polymerization: For example, poly ethane, Teflon, Polyvinyl chloride (PVC).

Condensation Polymerization: Examples include Nylon-6,6, Perylene, and Polyesters.

Classification Based on Monomers

Polyethene: In this type, a single type of monomer unit is present, namely Homomer.

Heteropolymer or co-polymer: It consists of different types of monomer units, such as nylon-6,6.

Classification Based on Molecular Forces

Elastomers: These are rubber-like solids in which weak interaction forces are present. For example, Rubber.

Fibres: They possess strong, tough, and high tensile strength, as well as strong forces of interaction. For example, nylon-6,6.

Thermoplastics: These have intermediate forces of attraction, such as polyvinyl chloride.

Thermosetting Polymers: These polymers significantly improve the material’s mechanical properties, as well as providing increased chemical and heat resistance. Examples of thermosetting polymers include phenolics, epoxies, and silicones.

Structure of Polymers

Most of the polymers around us are made up of a Hydrocarbon backbone. This backbone is a long chain of linked carbon and hydrogen atoms, made possible due to the tetravalent nature of carbon.

A few examples of hydrocarbon backbone polymers are polypropylene, polybutylene, and polystyrene. Additionally, there are polymers which have different elements in their backbone, such as Nylon which contains nitrogen atoms in the repeated unit backbone.

#Types of Polymers

On the basis of the type of the backbone chain, polymers can be divided into:

Organic Polymers: Carbon backbone with covalent bonds.

Inorganic Polymers: Backbone constituted by elements other than carbon.

Based on their synthesis:

Natural Polymers

Synthetic Polymers

Biodegradable Polymers

Biodegradable polymers are polymers that are degraded and decayed by microorganisms such as bacteria. These polymers are commonly used in surgical bandages, capsule coatings, and surgeries. For example, Poly hydroxybutyrate co vel (PHBV) is one such biodegradable polymer.

High-Temperature Polymers

These polymers are stable at high temperatures due to their high molecular weight. This makes them not easily destroyed even at very high temperatures. Therefore, they are extensively used in the healthcare industries, for making sterilization equipment and in the manufacturing of heat and shock-resistant objects.

Some of the important polymers are:

Polypropylene: It is a type of polymer that softens when heated to a certain temperature, and solidifies when cooled. Its malleability makes it a versatile material with many different uses.

The polymer is often utilized in a variety of applications, including stationary equipment, automotive components, reusable container speakers, and more. Thanks to its relatively low energy surface, the polymer can be welded instead of glued.

Polyethene: It is the most commonly found plastic around us. It is widely used in packaging materials, ranging from plastic bags to plastic bottles. There are different varieties of polyethene, but their common formula is (C2H4)*n.

Properties of Polymers

Physical Properties

As the length of the chain and the amount of cross-linking increases, the tensile strength of the polymer also increases.

Polymers do not melt; instead, they change state from crystalline to semi-crystalline.

Chemical Properties

The polymer is strengthened by hydrogen bonding and ionic bonding, resulting in improved cross-linking strength when compared to conventional molecules with different side molecules.

The high flexibility of the polymer is enabled by dipole-dipole bonding side chains.

Polymers with Van der Waals forces linking chains are known to be weak, yet they provide the polymer with a low melting point.

Optical Properties

Due to their ability to change their refractive index with temperature, PMMA and HEMA:MMA are used in lasers for spectroscopy and analytical applications.

Some Polymers and their Monomers

1. Nylon-6,6: Diamine and Dicarboxylic Acid
2. Polyethylene: Ethylene
3. Polyvinyl Chloride: Vinyl Chloride
4. Polystyrene: Styrene

Polypropene, also referred to as polypropylene, is composed of the monomer propene.

Polystyrene is an aromatic polymer, naturally transparent, composed of the monomer styrene.

Polyvinyl Chloride (PVC) is a plastic polymer composed of the monomer vinyl chloride.

The urea-formaldehyde resin is a non-transparent plastic obtained by heating formaldehyde and urea.

Glyptal is composed of the monomers ethylene glycol and phthalic acid.

Bakelite or polyoxybenzylmethylenglycolanhydride is a plastic which is composed of the monomers phenol and aldehyde.

#Types of Polymerization Reactions

Addition Polymerization

In Chain Growth Polymerization, small monomer units join together to form a large polymer chain. Each step of the reaction adds to the length of the chain, as seen in the example of ethane polymerization in the presence of peroxides.

Condensation Polymerization

Polymerization reactions that involve the elimination of small molecules such as H2O, CO, and NH3 are known as step growth polymerization. These reactions typically involve organic compounds containing bifunctional groups such as idols, -dials, diamines, and dicarboxylic acids. A common example of this type of reaction is the preparation of nylon -6, 6.

What is Copolymerization?

Copolymerization is a type of polymerization that involves two or more different monomers (small molecules) being joined together to form a single polymer chain.

Polymerization is the process in which two different monomers join together to form a polymer. An example of this process is the preparation of synthetic rubbers, such as BUNA-S.

How to Calculate Molecular Mass of Polymers?

To calculate the molecular mass of polymers, you need to determine the molecular weight of each monomer unit, multiply it by the number of monomer units in the polymer chain, and then add the molecular weights of all the monomer units together.

There are two types of average molecular masses of Polymers:

Average Molecular Masses of Numbers

Weighted Average Molecular Mass

Average Molecular Masses

The number average molecular mass of the polymer is given by $$\frac{N_1M_1 + N_2M_2 + N_3M_3 +\cdots}{N_1 + N_2 + N_3 + \cdots}$$

(\begin{array}{l}\bar{M} = \frac{\sum_{i=1}^{n} N_iM_i}{\sum_{i=1}^{n} N_i}\end{array} )

The average molecular mass (\bar{M_n} ) is determined by colligative properties, such as Osmotic Pressure, which affect the number of molecules in a solution.

Weighted Average Molecular Mass:

The weight average molecular mass of the polymer is given by $$\frac{m_1M_1 + m_2M_2 + m_3M_3 + \cdots}{m_1 + m_2 + m_3 + \cdots}$$ if $m_1, m_2, m_3\ldots$ are the masses of a macromolecule with molecular masses $M_1, M_2, M_3\ldots$, respectively.

(\overline{M}\omega = \frac{\sum{i=1}^{n} m_i M_i}{\sum_{i=1}^{n} m_i})

(\frac{\sum{miMi}}{\sum{mi}})

(\begin{array}{l}\Rightarrow \overline{M}_\omega = \frac{\sum N_iM_i \times M_i}{\sum N_iM_i}\end{array})

‘(\begin{array}{l} \Rightarrow \overline{M}_{\omega} = \frac{\sum N_i M_i^2}{\sum N_i M_i} \end{array})’

Polydispersive Index: It is the ratio of the Weight Average Molecular Mass to the Number Average Molecular Mass of Polymers.

(\begin{array}{l}PDI=\frac{\overline{M}_w}{\overline{M}_n}=1\end{array}) For natural polymers, PDI = 1.

#Uses of Polymers Polymers have a wide range of applications in various fields, including:

• Automotive industry
• Construction
• Electronics
• Medical
• Packaging
• Textiles
• Aerospace

Here are some of the important uses of polymers in our everyday life:

Polypropene is widely utilized across a variety of industries, including textiles, packaging, stationery, plastics, aircraft, construction, rope, toys, and more.

Polystyrene is a widely used plastic in the packaging industry. Everyday items such as bottles, toys, containers, trays, disposable glasses and plates, TV cabinets, and lids are all made from polystyrene. It is also used as an insulator.

The manufacture of sewage pipes is the most important use of polyvinyl chloride. Additionally, it is also used as an insulator in electric cables.

Polyvinyl chloride (PVC) has become a popular choice for doors, windows, furniture, clothing, and even vinyl flooring.

Urea-formaldehyde resins are commonly used in the production of adhesives, moulds, laminated sheets, and unbreakable containers.

Glyptal is used in the production of paints, coatings, and lacquers.

Bakelite is used for making electrical switches, kitchen products, toys, jewellery, firearms, insulators, and computer discs.

Uses of Polymers in Commercial Applications

Polymer	Monomer	Uses of Polymer

| Rubber | Isoprene (1, 2-methyl 1 – 1, 3-butadiene) | Used for making tyres and elastic materials |

| BUNA-S | (a) 1,3-Butadiene (b) Styrene | Synthetic Rubber |

| BUNA-N | (a) 1,3-Butadiene (b) Vinyl Cyanide | Synthetic Rubber |

| Teflon | Tetra Fluoro Ethane | Non-stick cookware – plastics |

| Terylene | (a) Ethylene glycol (b) Terephthalic acid | Fabric |

| Glyptal | (a) Ethylene glycol (b) Phthalic acid | Fabric |

| Bakelite | (a) Phenol (b) Formaldehyde | Plastic switches, Mugs, Buckets |

| PVC | Vinyl Cyanide | Tubes, Pipes |

| Melamine Formaldehyde Resin | (a) Melamine | (b) Formaldehyde | Ceramic plastic material |

| Nylon-6 | Caprolactam | Fabric |

FAQs on Polymers

What are some Examples of Polymers with Different Physical Properties?

Polymers are formed when monomers are joined by various molecular interactions. The type of interactions determines the properties of the polymer, such as elasticity, tensile strength, toughness, and thermal stability.

1. Monomers are linked together in a linear chain with weak bonding, resulting in polymers that are elastic and known as elastomers. Examples: Neoprene, Buna-S, Buna-R.

2. Polymers with strong intermolecular forces between the monomers and between the chains have higher tensile strength and are used as fibres, such as Polyamides (nylon6,6) and Polyesters (terylene).

Thermoplastics are polymers that have intermolecular forces between elastomers and fibres. They can be melted and reformed multiple times without much change in their properties. Examples: Polythene and Polyvinyl.

Thermosetting plastics, such as Bakelite and Urea-formaldehyde, are materials that cannot be reused or reprocessed after they undergo heavy branching and are fused on heating.

What is the Vulcanization of Rubber?

Adding 5% of sulphur to natural rubber enhances the crosslinking of the linear chains, improving its physical stability and stiffening it for applications such as vehicle tires.

Match Column A with Column B

| Column A | Column B |

| 1 | Buna-S | a | Ziegler-Natta Catalyst |

| 2 | Nylon 6-6 | B | Addition Polymerization |

| 3 | High-Density Polyethylene | C | Terephthalic Acid Ethylene Glycol |

| 4 | Declon | D | Biodegradable Polymer |

| 5 | Polymer of Glycine and Aminocaproic Acid | e | Fibre |

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| Column A | Column B |

| 1 | Buna-S | a | Addition Polymerization |

| 2 | Nylon 6-6 | b | Fiber |

| 3 | High-Density Polyethylene | C | Ziegler-Natta Catalyst |

| 4 | Declon | D | Terephthalic Acid |

| 5 | Polymer of glycine and aminocaproic acid | E | Biodegradable polymer |

What are Biodegradable Polymers?

Biodegradable polymers are polymers that can be broken down into smaller molecules by the action of living organisms, such as bacteria. Examples of biodegradable polymers include polylactic acid (PLA), polyhydroxyalkanoates (PHA), polycaprolactone (PCL), and polybutylene succinate (PBS).

Poly β-hydroxybutyrate-co-β-hydroxy valerate (PHBV) is an example of a polymer with functional groups found in natural polymers, and it can be degraded by bacterial presence.

Engineering plastics and synthetic metals refer to materials that are engineered to have properties similar to those of traditional plastics and metals, but with improved performance characteristics.

Polymers such as Silicone, Polycarbonate, ABS, and Polysulfone possess properties similar to ceramics and metals, including high strength and resistance to chemical, thermal, and abrasion, making them suitable for use in engineering applications.

Intrinsically conducting polymer (ICP), or sometimes referred to as ‘synthetic metal’, is a polymer that exhibits similar electrical, electronic, magnetic, and optical properties to that of a metal.