Monomers - Definition, Classification, Examples, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:56 PM IST

A monomer is a basic chemical compound for the formation of a large polymer chain by reacting together with another monomer molecule and the process involved is called polymerization. The polymer chain obtained is also called a three-dimensional network. The obtained molecule after the reaction and combination of monomer molecules is also called a macromolecule and we can say that a monomer molecule is the constitutional unit of the macromolecules.

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Classification of Monomers
Classification based on the synthesis
Condensation polymerization
Addition polymerization
Ring-opening polymerization
Monomers and polymers

Monomers can also be defined as small molecules that are joined together with the help of a bond to form a larger molecule. Before going into the definition of monomer let us discuss the molecules there are mainly two types of molecules that may be macromolecules and micro molecules. The one which has small molecules is called micro molecules so monomers belong to micromolecules. While the molecules obtained after the combination of monomers are joined molecules or macromolecules.

Polymerization of monomers

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Classification of Monomers

Monomers are chemical compounds consisting of atoms and molecules which then form a bond with each other and forms polymers or macromolecules. Natural and synthetic monomers are a very important classification of monomers.

Natural monomers

These types of monomers are found in nature and their organic molecules are combined together to form larger molecules or macromolecules. And these are responsible for the existence of life on our planet. They are biomolecules and are the building blocks of life on the earth. There are mainly five types of natural monomers, monosaccharides, amino acids, nucleotides, fatty acids, alcohols, and isoprene. Saccharides are natural monomers which then combined with form disaccharides and trisaccharides then polysaccharides.

The amino acids combined form the proteins. Amino acids are combined with peptide bonds. Nucleotides are building blocks of DNA and RNA that are the genetic material. The building blocks of lipids are alcohol and fatty acids. For natural rubber, the building block is isoprene that is isoprene monomers are combined together to form the natural rubber. So natural monomers are all present in the living organism naturally. Some of these important natural monomers can be explained in detail as follows.

Amino acids

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The presence of amino and the acidic groups that is carboxylic group give the name amino acids. These are the building blocks of proteins. 10,000 proteins are formed with 20 amino acids. True proteins contain the elements carbon, hydrogen, Sulphur, and nitrogen. Glycine, glutamine, valine, arginine, and cysteine are examples of amino acids.

Nucleotides

Nucleotides are the monomer unit for DNA and RNA. For DNA the monomer is deoxynucleotides and for RNA the nucleotide is a ribonucleotide. And also polynucleotides consist of a nitrogen base that is pyrimidine and purine linked with the sugar-phosphate. And these are commonly found in the nucleus of the cell.

RNA and DNA

Monosaccharides

These are the simplest unit of carbohydrates. The monomer for carbohydrates is monosaccharides and contains glycosidic linkages. Glucose is the very important and most abundant monosaccharide. One of the very important monomer units is glucose and is the most abundant natural monomer found and is then combined with glycosidic bonds to form the polymers cellulose, starch, etc.

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Isoprene

The monomer unit of natural rubber is isoprene. Isoprene combined to form cis 1, 4 polyisoprene and trans 1, 4 polymers. Of which cis polyisoprene is commonly seen and important.

Natural rubber

Synthetic monomers

These are man-made or artificially found monomers that are then combined to form polymers that are useful for mankind. Its means that the building blocks that are the monomers are synthesized artificially with the help of different atoms and which then reacted together to form the molecules that can be used in various applications of human needs. For example, ethylene is a monomeric unit that is in the size and artificially for the production of polyethylene. tetrafluoroethylene which is a derivative of ethylene is prepared artificially for the production of a Teflon. Another important example of a synthetic monomer is caprolactam.

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Classification based on the synthesis

Based on the mode of synthesis of polymers from monomers they are adopted to form polymers they can be classified as one that participates in a condensation polymerization and the one that participates in addition polymerization.

Condensation polymerization

The monomer molecules that can lose small molecules as by-products like water, alcohol accepted in order to form a polymer is called condensation polymer. Some of the common condensation polymers obtained poly amides proteins, polyacetals. The monomers of condensation polymers are amide, etc.

Addition polymerization

This type of polymerization does not involve the generation of by-products like water, alcohol acceptors during their combination is addition polymers. It involves some simple molecules like alkenes, alkynes, etc. that are merely unsaturated compounds with the help of a free radical mechanism addition polymerization of them takes place. For example, the monomer olefin combined in an addition reaction for the formation of polyolefins.

This can also be initiated with the help of carbanions, metal complexes. PVC, polypropylene, Teflon, polystyrene, etc. are examples of additional polymers. The copolymer is also a type of addition polymer in which different types of monomers undergo an addition polymerization reaction for the formation of copolymers. One such example is the addition reaction of vinylidene chloride and vinyl chloride for the formation of Saran wrap.

Ring-opening polymerization

Some monomers that are of a ring or cyclic structure undergo polymerization for the formation of the ring-opening polymerization reaction. For example by the ring-opening reaction of ethylene oxide polyethylene glycol is formed.

Monomers and polymers

Monomers are micro molecules while polymers are macromolecules formed by the combination and reaction of monomer units. So polymers are chains consisting of many units of monomers. A single monomer unit can get combined with two other monomer units. Depending on the kind of monomer present polymers are classified as homopolymer and heteropolymers.

When monomer units of the same type are combined it is called homopolymer while different types of monomers when combined which result in the formation of heteropolymers. PVC, polystyrene, etc. are all polymers formed from monomers. Monomer and polymers are interconnected.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. Define monomers.

Small organic molecules can combine or react together to form giant molecules or macromolecules. That has a very important application for the existence of life. There are two types of monomers. The one that is found in nature itself is a natural monomer and one that is synthesized artificially is man-made or synthetic monomers. These are synthesized for many industrial applications. Isoprene is a natural monomer while ethylene is a synthetic monomer.

2. Give some monomer examples?

Some of the monomers are amino acids, ethylene, amino acids, glucose, isoprene, etc.

3. What is a monomer?

These are atoms or small organic molecules that when combined through some chemical reactions to form the chain of monomer units called the polymers. Polymers are very important.

4. What is a monomer?

A monomer is a small, simple molecule that can bond with other identical molecules to form a larger, more complex structure called a polymer. Monomers are the building blocks of polymers, much like how individual bricks make up a wall.

5. What is monomer meaning?

Monomer definition is given as, the molecule or atom that can form a bond with an identical or different molecule to form a macromolecule or giant molecule. And the compound formed after the chemical reactions is a polymer molecule, and it has much application in the industrial field.

6. What are monomers and polymers?

Monomers are the smallest repeating unit of polymers. Monomers are micro molecules while polymers are macromolecules formed by the reaction and combination of monomer units. An example of a monomer is isoprene and the polymer obtained from them is the natural rubber.

7. Which of the following is a monomer?

Glucose
Starch
Cellulose
Glycogen

Answer: a) Glucose

8. What are nucleic acid monomers?

5-carbon sugar
nitrogenous base
phosphate group

9. Write the glycogen monomer.

Glucose is the monomer of glycogen.

10. What is the difference between addition and condensation monomers?

Addition monomers, like ethylene, have double bonds that open up during polymerization without losing any atoms. Condensation monomers, such as amino acids, react by losing small molecules (often water) during polymerization.

11. Can you give examples of synthetic monomers?

Synthetic monomers include ethylene (forms polyethylene), styrene (forms polystyrene), and vinyl chloride (forms polyvinyl chloride or PVC). These are typically derived from petroleum products and are used to create many common plastics.

12. Can monomers react with themselves to form polymers?

Yes, many monomers can react with themselves to form homopolymers. This process is called self-polymerization. For example, styrene can polymerize with itself to form polystyrene.

13. What are some common functional groups found in monomers?

Common functional groups in monomers include double bonds (alkenes), carboxyl groups, amino groups, and hydroxyl groups. These groups often participate in the polymerization reaction and influence the polymer's properties.

14. What is the concept of monomer reactivity ratios in copolymerization?

Monomer reactivity ratios describe the relative rates at which different monomers add to a growing polymer chain in copolymerization. These ratios help predict the composition and sequence distribution of monomers in the resulting copolymer.

15. What is the role of monomers in conducting polymers?

Certain monomers, like aniline or pyrrole, can form polymers with conjugated double bonds along their backbone. This conjugation allows for electron movement, making the polymer electrically conductive. The specific monomer structure influences the degree of conductivity.

16. How do cyclic monomers differ from linear monomers in polymerization?

Cyclic monomers undergo ring-opening polymerization, where the ring structure opens to form a linear polymer chain. This differs from linear monomers, which typically polymerize through addition or condensation reactions without changing their basic structure.

17. What is the significance of monomer orientation in polymer properties?

Monomer orientation in the polymer chain can significantly affect properties like crystallinity, optical characteristics, and mechanical strength. For example, in polypropylene, the orientation of methyl groups determines whether the polymer is isotactic, syndiotactic, or atactic.

18. What is the concept of monomer feed ratio in copolymerization?

The monomer feed ratio refers to the relative amounts of different monomers used in a copolymerization reaction. This ratio, along with the monomers' reactivity ratios, influences the composition and properties of the resulting copolymer.

19. What is the role of monomers in shape-memory polymers?

In shape-memory polymers, the choice of monomers affects the polymer's ability to remember and return to its original shape after deformation. Monomers that allow for reversible cross-linking or crystallization are often used in these materials.

20. How are monomers classified?

Monomers can be classified based on their chemical structure, origin, or the type of polymer they form. Common classifications include natural vs. synthetic monomers, organic vs. inorganic monomers, and those that form addition polymers vs. condensation polymers.

21. What are some examples of natural monomers?

Natural monomers include glucose (forms cellulose and starch), amino acids (form proteins), and nucleotides (form DNA and RNA). These are found in living organisms and form biopolymers essential for life.

22. What is meant by the term "functionality" when discussing monomers?

Functionality refers to the number of reactive sites on a monomer that can participate in forming bonds during polymerization. For example, a monomer with two reactive sites is called bifunctional, while one with three is trifunctional.

23. How does monomer functionality affect polymer structure?

Monomer functionality determines whether the resulting polymer will be linear, branched, or cross-linked. Bifunctional monomers typically form linear polymers, while monomers with higher functionality can create branched or cross-linked structures.

24. How do monomers differ in their ability to form crystalline or amorphous polymers?

The structure and symmetry of monomers influence the polymer's ability to form crystalline or amorphous regions. Symmetrical monomers often lead to more crystalline polymers, while asymmetrical or bulky monomers tend to form more amorphous structures.

25. What are some examples of monomers used in biodegradable polymers?

Examples include lactic acid (used in polylactic acid or PLA), glycolic acid (used in polyglycolic acid), and ε-caprolactone (used in polycaprolactone). These monomers form polymers that can be broken down by natural processes.

26. What is the role of monomers in polymer recycling?

Understanding the monomer composition of polymers is crucial for effective recycling. Some polymers can be broken down into their original monomers (depolymerization), which can then be reused to create new polymers, promoting a circular economy.

27. What is the significance of monomer purity in polymer production?

Monomer purity is crucial in polymer production as impurities can interfere with the polymerization process, leading to defects in the polymer structure or undesired properties in the final product.

28. How do monomers contribute to the mechanical properties of polymers?

The structure and interactions between monomers determine a polymer's mechanical properties. Factors like monomer size, shape, and intermolecular forces affect properties such as tensile strength, elasticity, and impact resistance.

29. How do monomers influence the glass transition temperature of polymers?

The chemical structure of monomers, including their size, flexibility, and intermolecular forces, directly affects the glass transition temperature of the resulting polymer. This temperature marks the transition between rigid and more flexible states of the polymer.

30. How do monomers differ from polymers?

Monomers are single, individual units, while polymers are large molecules made up of many repeating monomer units. Think of monomers as individual links and polymers as the entire chain.

31. What types of bonds typically connect monomers to form polymers?

Monomers usually connect through covalent bonds to form polymers. The specific type of bond can vary, but common examples include carbon-carbon single bonds, double bonds, or other functional group interactions.

32. What is the process called when monomers join together to form a polymer?

The process of monomers joining together to form a polymer is called polymerization. This can occur through various mechanisms, such as addition polymerization or condensation polymerization.

33. How does the structure of a monomer affect the properties of the resulting polymer?

The structure of a monomer greatly influences the polymer's properties. Factors like the monomer's size, shape, and chemical composition determine characteristics such as the polymer's strength, flexibility, melting point, and chemical reactivity.

34. What role do catalysts play in monomer polymerization?

Catalysts can initiate, accelerate, or control the polymerization process. They lower the activation energy required for monomers to react, allowing polymerization to occur more quickly or under milder conditions.

35. Can different types of monomers combine to form a polymer?

Yes, different types of monomers can combine to form copolymers. When two or more different monomers are used, the resulting polymer is called a copolymer. This is in contrast to homopolymers, which are made from only one type of monomer.

36. How do temperature and pressure affect monomer behavior during polymerization?

Temperature and pressure can significantly influence polymerization. Higher temperatures generally increase reaction rates and can affect the polymer's structure. Increased pressure can promote polymerization in some cases, especially for gaseous monomers.

37. What is a monomer's degree of polymerization?

The degree of polymerization refers to the number of monomer units in a polymer chain. It's an average value that indicates the polymer's chain length and can greatly affect the material's properties.

38. How do monomers contribute to the biodegradability of polymers?

The chemical structure of monomers determines how easily microorganisms can break down the resulting polymer. Natural monomers often form more biodegradable polymers, while many synthetic monomers create polymers resistant to biodegradation.

39. How do monomers contribute to the thermal stability of polymers?

The chemical structure of monomers, including the presence of aromatic rings or strong intermolecular forces, can enhance a polymer's thermal stability. Monomers that form strong covalent bonds or promote cross-linking often result in more heat-resistant polymers.

40. How do monomers contribute to the solubility of polymers?

The chemical nature of monomers, including their polarity and ability to form hydrogen bonds, determines the solubility of the resulting polymer. Hydrophilic monomers often lead to water-soluble polymers, while hydrophobic monomers result in polymers that are soluble in non-polar solvents.

41. How do monomers affect the optical properties of polymers?

The chemical structure of monomers can influence a polymer's interaction with light. For example, monomers with conjugated systems can absorb specific wavelengths of light, affecting the polymer's color. Some monomers can also lead to polymers with high refractive indices or transparency.

42. What is the importance of monomer sequence in proteins?

In proteins, the sequence of amino acid monomers (primary structure) determines the protein's three-dimensional shape and, consequently, its function. Even small changes in this sequence can dramatically alter the protein's properties and biological activity.

43. How do monomers contribute to the flame retardancy of polymers?

Some monomers contain elements like chlorine, bromine, or phosphorus that can impart flame-retardant properties to the resulting polymer. These elements can interfere with the combustion process or promote char formation, enhancing the polymer's resistance to fire.

44. How do monomers affect the gas permeability of polymers?

The structure of monomers influences the free volume and chain mobility in polymers, which in turn affects gas permeability. Rigid monomers or those promoting crystallinity often lead to polymers with lower gas permeability, while flexible monomers can increase permeability.

45. How do monomers contribute to the hydrolytic stability of polymers?

The chemical nature of monomers, particularly their susceptibility to react with water, determines a polymer's hydrolytic stability. Monomers forming hydrolysis-resistant bonds (like carbon-carbon bonds) lead to more stable polymers, while those forming easily hydrolyzed bonds (like esters) result in less stable polymers.

46. What is the significance of monomer symmetry in polymer crystallization?

Monomer symmetry plays a crucial role in polymer crystallization. Symmetrical monomers often lead to polymers that can pack more efficiently, promoting crystallization. Asymmetrical or bulky monomers typically result in more amorphous polymers.

47. How do monomers influence the weathering resistance of polymers?

The chemical structure of monomers affects a polymer's resistance to environmental factors like UV radiation, moisture, and temperature fluctuations. Monomers that form strong bonds or incorporate UV-absorbing groups can enhance a polymer's weathering resistance.

48. What is the role of monomers in self-healing polymers?

In self-healing polymers, monomers or polymer segments are designed to reform bonds after damage. This can involve monomers capable of reversible reactions or those that can flow and reconnect under certain conditions, allowing the material to repair itself.

49. How do monomers affect the dyeability of polymers?

The chemical structure of monomers influences a polymer's ability to accept and retain dyes. Monomers that introduce polar groups or allow for hydrogen bonding can enhance a polymer's dyeability by providing sites for dye molecules to attach.

50. What is the importance of monomer polarity in polymer adhesion?

Monomer polarity affects the surface energy of the resulting polymer, which in turn influences its adhesive properties. Polar monomers often lead to polymers with better adhesion to other polar surfaces, while non-polar monomers result in polymers that adhere better to non-polar surfaces.

51. How do monomers contribute to the chemical resistance of polymers?

The chemical structure of monomers determines a polymer's resistance to various chemicals. Monomers that form strong, stable bonds or create dense, crystalline regions often result in polymers with higher chemical resistance.

52. What is the role of monomers in polymer blend compatibility?

The chemical similarity or complementarity of monomers in different polymers can affect their miscibility in blends. Polymers made from similar or compatible monomers are more likely to form homogeneous blends, while those from very different monomers may phase separate.

53. How do monomers influence the tacticity of polymers?

The structure of monomers, particularly those with substituents, determines the possible tacticities (isotactic, syndiotactic, or atactic) of the resulting polymer. This arrangement of substituents along the polymer chain significantly affects its properties.

54. What is the significance of monomer size in polymer chain entanglement?

The size and shape of monomers affect the ability of polymer chains to entangle with each other. Larger, bulkier monomers often lead to less chain entanglement, while smaller, more flexible monomers can result in greater entanglement, influencing properties like melt viscosity and mechanical strength.

55. How do monomers contribute to the barrier properties of polymers?

The chemical structure of monomers affects a polymer's ability to prevent the passage of gases, liquids, or other substances. Monomers that promote crystallinity or strong intermolecular interactions often lead to polymers with better barrier properties.

56. What is the role of monomers in determining the glass transition temperature of polymers?

The structure of monomers, including their size, flexibility, and intermolecular forces, directly influences the glass transition temperature (Tg) of the resulting polymer. Rigid monomers or those promoting strong interactions typically lead to higher Tg values.

57. How do monomers affect the processability of polymers?

The structure of monomers influences a polymer's melting point, melt viscosity, and other properties that affect its processability. Monomers that allow for easy chain movement or prevent strong intermolecular interactions often lead to more easily processed polymers.

58. What is the importance of monomer design in creating polymers for specific applications?

Monomer design is crucial in tailoring polymers for specific applications. By carefully selecting or modifying monomer structures, scientists can create polymers with desired properties such as strength, flexibility, conductivity, or biocompatibility, opening up new possibilities in various fields from medicine to electronics.