Bihar Board - Class 12 Chemistry - Chapter 15: Polymers Handwritten Notes

Polymers are large molecules made up of repeating structural units called monomers, which are chemically bonded together. These macromolecules are found in various natural and synthetic forms and have diverse applications in daily life. Polymers can be classified into two main categories: natural polymers, such as proteins, starch, and rubber, and synthetic polymers, such as plastics like polyethylene and polystyrene. The chapter explores the types, preparation methods, properties, and uses of polymers.

Key Points:

1. Definition and Structure:

   • Polymers are long-chain molecules formed by the repeated bonding of smaller units called monomers.
   • They can have linear, branched, or cross-linked structures, which affect their properties and uses.

2. Types of Polymers:

   • Natural Polymers: These occur in nature and include proteins, cellulose, rubber, and starch. They play vital roles in biological processes.
   • Synthetic Polymers: These are man-made and include plastics like polyethylene, nylon, and PVC. They are used in a wide range of products from packaging to clothing.

3. Polymerization:

   • Polymers are formed through polymerization, which involves two main types:
     • Addition Polymerization: Monomers with unsaturated bonds (like alkenes) add together without the loss of any atoms. Examples include polyethylene and polystyrene.
     • Condensation Polymerization: Monomers with two or more functional groups combine, releasing small molecules (like water or alcohol). Examples include nylon and Bakelite.

4. Properties of Polymers:

   • Thermoplastic Polymers: These can be melted and reformed multiple times (e.g., polyethylene, PVC).
   • Thermosetting Polymers: These harden permanently after being shaped and cannot be re-melted (e.g., Bakelite, melamine).
   • Polymers can be flexible, tough, or rigid depending on their structure and the type of monomers used.

5. Uses of Polymers:

   • Plastics: Used in packaging, containers, and toys (e.g., polyethylene, polypropylene).
   • Fibers: Used in textiles and fabrics (e.g., nylon, polyester).
   • Elastomers: Used for rubber products like tires and gaskets (e.g., natural rubber, neoprene).
   • Biodegradable Polymers: These are environmentally friendly alternatives to conventional plastics (e.g., polylactic acid or PLA).

6. Environmental Impact:

   • Synthetic polymers, especially plastics, are a major source of pollution due to their non-biodegradable nature.
   • Biodegradable polymers are being developed as alternatives to reduce the environmental impact.

Conclusion:

Polymers are an essential part of modern life, with their presence in everything from packaging to clothing to medical devices. Understanding the different types of polymers, their synthesis, properties, and uses is crucial in fields such as material science, chemistry, and environmental studies. While synthetic polymers provide a wide range of applications, the challenge of their environmental impact has led to the development of more sustainable, biodegradable alternatives. Polymers continue to evolve, offering innovative solutions to everyday challenges.