What is the Difference Between Addition and Condensation Polymerization?
Polymerization is essential in chemistry and helps students understand various practical and theoretical applications related to this topic.
What is Polymerization in Chemistry?
A polymerization reaction is a chemical process where many small molecules called monomers join together to form long-chain macromolecules known as polymers. This concept appears in chapters related to organic chemistry, industrial material science, and biomolecules, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
The molecular formula of a polymerization product varies based on the monomer used. For example, polythene has the general formula (C2H4)n. Polymers are macromolecules made by repeating these monomeric units, categorized under organic and high-molecular-weight compounds. During polymerization, simple monomers, such as ethene, combine to form large chains with unique properties.
Preparation and Synthesis Methods
Polymerization can occur naturally (e.g., proteins, DNA) or be performed in laboratories and industries to create synthetic polymers (e.g., plastic, nylon). The main methods are:
- Addition polymerization: Unsaturated monomers (with double/triple bonds) combine without forming by-products. Initiators or catalysts like peroxides often speed up this process.
- Condensation polymerization: Two different monomers react, producing the polymer and a small molecule such as H2O or HCl as a by-product.
Techniques used include bulk, solution, suspension, and emulsion polymerization. For example, polyethylene is made using addition polymerization in the presence of a Ziegler-Natta catalyst.
Physical Properties of Polymerization Products
Properties depend on the type of polymer formed. Most polymers have high tensile strength, flexibility, varying melting/boiling points, and can be either thermoplastic (soften on heating) or thermosetting (harden permanently). Some are rigid while others are elastic, and their solubility varies. For example, polythene is flexible, chemically inert, and electrically insulating.
Chemical Properties and Reactions
Polymers generally show stability towards acids and bases but can break down at very high temperatures (thermal decomposition). Chain polymers often show non-reactivity, while those with polar groups may be more sensitive to chemicals. Crosslinking during polymerization provides rigidity, as in Bakelite formation through condensation polymerization.
Frequent Related Errors
- Confusing polymerization with general condensation or only associating it with plastics.
- Mixing up addition and condensation mechanisms or forgetting the by-products in condensation reactions.
- Assuming all polymers are artificial when many are naturally occurring biopolymers.
Uses of Polymerization in Real Life
Polymerization is widely used in industries like packaging (polythene bags and bottles), textiles (nylon, polyester), construction (PVC pipes), electronics (insulation), and healthcare (disposable gloves, syringes). Many common materials, such as tires, clothing fibers, and bioplastics, are the result of different polymerization processes. In nature, it forms essential molecules like DNA, proteins, and starch.
Relevance in Competitive Exams
Students preparing for NEET, JEE, and Olympiads should be familiar with polymerization, as it often features in reaction-based and concept-testing questions. Knowing the difference between addition and condensation polymerization, properties of polymers, and their practical uses is very important for MCQs and subjective questions.
Relation with Other Chemistry Concepts
Polymerization is closely related to topics such as polymer chemistry and biopolymers, helping students build a conceptual bridge between organic reactions, structure of materials, and even biological macromolecules. For further details, you can also see monomers and synthetic polymers.
Step-by-Step Reaction Example
- Start with the reaction setup.
Let’s consider the addition polymerization of ethene to form polythene:
nCH2=CH2 → (C2H4)n - Explain each intermediate or by-product.
Under high pressure and a suitable catalyst (like Ziegler-Natta), the double bond breaks and single bonds form, joining monomers in a long chain. No by-product is formed in addition polymerization.
Lab or Experimental Tips
Remember polymerization by the rule of “repeating units.” Check for a catalyst or initiator and note if any small molecule is released during synthesis. Vedantu educators often use colored diagrams and hands-on demonstrations to make this topic clear in online classes.
Try This Yourself
- State one main difference between addition and condensation polymerization.
- Identify two products made from condensation polymerization.
- Draw the repeating unit for polythene and name the monomer used.
Final Wrap-Up
We explored polymerization—its definition, types, mechanisms, properties, and everyday impact. For more in-depth explanations, practice questions, or live doubt sessions, access detailed chemistry notes and classes on Vedantu.
FAQs on Polymerization in Chemistry: Definition, Types, and Examples
1. What is polymerization and why is it important?
Polymerization is a chemical process where small molecules, called monomers, combine to form a much larger chain-like or network molecule called a polymer. Its importance stems from the creation of materials with unique properties like high strength, elasticity, and durability—properties not present in the individual monomers. These materials, including plastics, rubbers, and fibers, are essential in countless everyday and industrial applications.
2. What is the main difference between addition and condensation polymerization?
The key difference lies in how monomers combine and whether by-products are formed. In addition polymerization, monomers with double or triple bonds add to each other sequentially, creating a long chain without losing any atoms. Condensation polymerization, however, involves a reaction between two different functional groups on monomers, forming the polymer and eliminating a small molecule, such as water (H₂O) or hydrogen chloride (HCl).
3. Can you provide an example of polymerization from daily life?
A common example is the creation of polythene (polyethylene), used in plastic bags and bottles. This happens through addition polymerization of ethene (C₂H₄) monomers. Under specific conditions (high pressure, temperature, and a catalyst), many ethene molecules link together, breaking their double bonds to form the long, saturated chains of polythene.
4. What are the key steps involved in a typical chain-growth polymerization reaction?
A typical chain-growth polymerization, like free-radical polymerization, involves three main steps:
• Initiation: An initiator creates a highly reactive free radical that attacks a monomer, starting the polymer chain.
• Propagation: The monomer radical adds to another monomer, rapidly increasing the chain length.
• Termination: Chain growth stops when two active chains react with each other or an inhibitor, ending the process.
5. How do homopolymers and copolymers differ?
The difference lies in the types of monomer units used. A homopolymer is made from only one type of monomer (e.g., polythene, made only from ethene units). A copolymer uses two or more different monomers (e.g., Buna-S rubber, made from 1,3-butadiene and styrene).
6. What is the significance of the 'degree of polymerization' for a polymer's properties?
The degree of polymerization (DP), the number of monomer units in a polymer chain, significantly impacts its physical properties. A higher DP generally means a higher molecular mass, resulting in increased tensile strength, toughness, melting/boiling points, and viscosity.
7. How is polymerization relevant in biological systems?
Polymerization, or biopolymerization, is fundamental in biology, creating essential macromolecules. Examples include:
• Proteins (polymers of amino acids)
• DNA and RNA (polymers of nucleotides)
• Polysaccharides (polymers of sugars like glucose) These biopolymers perform crucial roles from catalysis and structure to genetic information storage.
8. Why are not all polymers considered plastics?
While all plastics are polymers, the reverse isn't true. 'Plastic' refers to a polymer moldable by heat and pressure (showing plasticity). Many natural polymers like cellulose (in wood and cotton) or keratin (in hair) are naturally rigid and aren't plastics unless chemically modified.
9. What makes some polymerization reactions hazardous?
Many chain-growth polymerization reactions are highly exothermic, releasing considerable heat. Poor heat management can lead to an uncontrolled increase in reaction rate, causing a dangerous temperature and pressure build-up—a runaway reaction—potentially resulting in explosions or fires.
10. What are common industrial polymerization techniques?
Industrial polymerization uses several techniques, chosen based on factors like monomer type, desired polymer properties, and cost. These include:
• Bulk polymerization (monomer and catalyst only)
• Solution polymerization (monomer dissolved in a solvent)
• Suspension polymerization (monomer suspended as droplets)
• Emulsion polymerization (monomer emulsified in water).
11. What are some examples of condensation polymers?
Condensation polymers are formed by the reaction between two different bifunctional or tri-functional monomer units, with the elimination of a small molecule like water. Examples include nylon, Bakelite, and certain types of polyesters.
12. What are some examples of addition polymers?
Addition polymers are formed by the addition of monomers with double or triple bonds, without the loss of any atoms. Examples include polyethylene (polythene), polypropylene, and polyvinyl chloride (PVC).
