Explain structure of polyacrylonitrile.
Explain structure of polyacrylonitrile.
Solution and Explanation
Solution: Structure of Polyacrylonitrile (PAN)
Polyacrylonitrile (PAN) is a synthetic polymer with significant applications in various industries, including textiles, carbon fiber production, and as a precursor for various materials due to its strength and heat resistance. It is formed by the polymerization of the monomer acrylonitrile.
Polymerization of Acrylonitrile:
Polyacrylonitrile is a polymer made from repeating units of acrylonitrile. The chemical structure of polyacrylonitrile can be represented by the following repeating unit:
[-CH2-CH(CN)-]n
Here, the structure consists of two main components:
- -CH2-: This represents the ethylene unit (C2H4), which is the backbone of the polymer chain.
- -CH(CN)-: This represents the acrylonitrile unit (CH2=CH-CN), where the nitrile group (-CN) is attached to the carbon atom.
The "n" in the formula indicates that these repeating units continue in a chain to form a long polymer. The nitrile group (-CN) contributes to the polymer's polarity and chemical reactivity, which gives PAN its distinct properties such as high strength, solvent resistance, and thermal stability.
Properties of Polyacrylonitrile:
Polyacrylonitrile has several important properties that make it a versatile material:
- High tensile strength: PAN is known for its strong and durable fibers.
- Thermal stability: PAN can withstand high temperatures without significant degradation.
- Solvent resistance: PAN is resistant to most solvents, making it ideal for various chemical processes.
Applications of Polyacrylonitrile:
Polyacrylonitrile is used in a wide range of applications, including:
- Textile fibers (e.g., acrylic fibers)
- Carbon fiber production
- Filtration materials
- Battery separators
Conclusion:
The structure of polyacrylonitrile consists of repeating units of acrylonitrile, where the ethylene group serves as the backbone, and the nitrile group (-CN) contributes to its chemical and physical properties. The polymerization of acrylonitrile results in a high-strength, heat-resistant material with various industrial applications.
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Concepts Used:
Types of Polymerization Reactions
Polymerization is a chemical reaction in which a large number of monomer molecules combine to produce a polymer. A polymerization can yield macromolecules with a linear or branching structure. They can also take the form of a three-dimensional complicated network.
Types of Polymerisation
Polymerization reactions are divided into two groups, namely, Addition polymerization (chain reaction) and condensation reaction (step reaction).
- Addition Polymerisation: As the name denotes, we can see the addition of monomers to form a polymer, twice the number or even more than that. Here, we can either select monomers of the same species or of different species. When we choose the single species monomers for the polymerization, the product thus formed is known as homopolymer (for example polythene used to make bags). When we use two different species for additional polymerization, the polymer would be known as copolymer (for example, Buna-S and Buna-N).
- Condensation Polymerisation: In the condensation polymerisation, we can find elimination of compounds like HCL, water, alcohol etc...; while the monomers condense during the reaction process. This reaction happens between tri-function and bi-function monomer units and results in the formation of polymers like nylon.