Polymer Chemistry

Step 1: Recall the main types of polymerization.
There are mainly two recognized types of polymerization: Addition and Condensation.
In addition polymerization, monomers add one after another without eliminating by-products.
In condensation polymerization, monomers join and eliminate small molecules like water, HCl, or alcohol.
Step 2: Focus on fiber formation.
Most synthetic fibers such as Nylon-6,6 and Polyester (Terylene) are prepared by condensation polymerization.
For example: Nylon-6,6 is formed when hexamethylene diamine reacts with adipic acid, and water is liberated as a by-product.
Similarly, Terylene (a polyester) is produced from terephthalic acid and ethylene glycol with the elimination of water.
Step 3: Analyze each option.
- (A) Addition Polymerization: In this, no by-products are formed, so it does not match the question.
- (B) Condensation Polymerization: Correct. This process liberates by-products like water or HCl during polymer formation.
- (C) Subtraction Polymerization: Not a recognized type of polymerization.
- (D) Reduction Polymerization: Incorrect, not related to polymer formation in this context.
Step 4: Conclusion.
Hence, the polymerization in which fibers are formed by joining monomers with the elimination of by-products is Condensation Polymerization.

Step 1: Definition of copolymers.
When two or more different types of monomers combine to form a polymer chain, the resulting polymer is called a copolymer.
Copolymers are very important in industry because they allow scientists to tailor properties like strength, elasticity, and heat resistance.
Step 2: Explanation of the four types.
- Random Copolymer: Monomers are arranged in a random order. Example: Styrene-butadiene rubber.
- Block Copolymer: Large blocks of one monomer are followed by blocks of another. Example: Styrene-butadiene-styrene (SBS).
- Alternating Copolymer: Monomers alternate strictly one after the other. Example: Styrene-maleic anhydride copolymer.
- Graft Copolymer: A main chain of one type with side branches of another type. Example: High-impact polystyrene (HIPS).
Step 3: Option analysis.
- Option 1 (A, B, D only): Incorrect, because alternating copolymer is also a valid subcategory.
- Option 2 (A, B, C only): Incorrect, because graft copolymer is missing.
- Option 3 (A, B, C and D only): Correct, as all four are valid.
- Option 4 (B, C and D only): Incorrect, because random copolymer is valid too.
Step 4: Conclusion.
Therefore, all four types are valid subcategories of copolymers.