Understanding Copolymers and Homopolymers

Polymers are large molecules formed by joining together many small repeating units called monomers. Based on the type of monomers used, polymers can be classified as homopolymers or copolymers.

• Homopolymer: A polymer formed from only one type of monomer unit. The repeating structural unit in a homopolymer is derived from a single monomer.
• Copolymer: A polymer formed from two or more different types of monomer units. The repeating structural units in a copolymer are derived from different monomers.

Analyzing the Given Polymers

Let's examine the monomers that make up each of the given polymers to determine if they are homopolymers or copolymers.

1. Polypropene

Polypropene is formed by the polymerization of only one type of monomer, propene.

Monomer: Propene ($$\text{CH}_2=\text{CHCH}_3$$)

Since it is made from a single type of monomer, Polypropene is a homopolymer.

2. Polystyrene

Polystyrene is formed by the polymerization of only one type of monomer, styrene.

Monomer: Styrene ($$\text{C}_6\text{H}_5\text{CH}=\text{CH}_2$$)

Since it is made from a single type of monomer, Polystyrene is a homopolymer.

3. Polyvinyl Chloride (PVC)

Polyvinyl chloride is formed by the polymerization of only one type of monomer, vinyl chloride.

Monomer: Vinyl chloride ($$\text{CH}_2=\text{CHCl}$$)

Since it is made from a single type of monomer, Polyvinyl chloride is a homopolymer.

4. Glyptal

Glyptal is a type of polyester resin. It is formed by the condensation polymerization of two different monomers:

• Ethylene glycol ($$\text{HOCH}_2\text{CH}_2\text{OH}$$)
• Phthalic acid (or Phthalic anhydride) ($$\text{C}_6\text{H}_4(\text{COOH})_2$$ or the corresponding anhydride)

Since Glyptal is formed from two different types of monomers (ethylene glycol and phthalic acid), it is a copolymer.

Conclusion

Based on the analysis of the monomers, Glyptal is the only polymer among the options that is formed from two different monomer units, making it a copolymer. Polypropene, Polystyrene, and Polyvinyl chloride are all formed from single monomer units and are therefore homopolymers.

Revision Table: Polymer Classification

Additional Information: Types of Copolymers

Copolymers can be further classified based on how the different monomer units are arranged along the polymer chain. The main types include:

• Alternating copolymers: Monomers are arranged in a regular alternating sequence (e.g., A-B-A-B-A-B...).
• Random copolymers: Monomers are arranged in a random sequence along the chain (e.g., A-A-B-A-B-B-A...).
• Block copolymers: Blocks of each monomer are arranged sequentially (e.g., A-A-A-A-B-B-B-B...).
• Graft copolymers: Chains of one type of monomer are branched onto a backbone chain of another type of monomer.

Glyptal, being a polyester formed by condensation, typically has an alternating or somewhat random arrangement depending on the exact reaction conditions, but its key characteristic as a copolymer is the presence of two different monomer types.