A large number of simple molecules called monomers combine together to form a macromolecule called a polymer. Each polymer has a repeating structural unit. If the repeating structural unit is derived from one type of monomer molecules. The polymer is said to be a homopolymer and if it is derived from two or more different types of monomer molecules , the polymer is said to be a copolmer. Both homopolymers and copolymers may be formed either by addition or condensation reactions. Alkenes and dienes polymerize by addition (chain growth) mechanism involving carbocations , carbanions or free radical intermediates. Dienes (chloroprene, isoprene, etc.) polymerize by 1, 4-addition mechanism to give cis-or trans-polymers. Natural rubber is quite soft and tacky but these properties can be improved by a process called vulcanization.
In contrast , bifunctional monomer molecules undergo , condensation or step-growth polymerization. Polymers which can be heated and reshaped as many times as desired are called thermoplastics , (polythene, polystyrene, PVC, teflon, etc.) while those which can be heated only once to give a particular shape are called thermosetting polymers (bakelite, melmac, etc.).
Teflon, styron and neoprene are all

Options

A. copolymers
B. condensation polymers
C. homopolymers
D. monomers.

Answer

**Step-by-Step Solution:**

1. **Understanding Monomers and Polymers:**
- A polymer is a large molecule made up of repeating structural units called monomers.
- Monomers can be simple molecules that combine through chemical reactions to form polymers.

2. **Types of Polymers:**
- **Homopolymers:** Formed from one type of monomer. For example, polyethylene is made from the monomer ethylene.
- **Copolymers:** Formed from two or more different types of monomers. An example is styrene-butadiene rubber, which is made from styrene and butadiene.

3. **Polymerization Mechanisms:**
- Polymers can be formed through two main mechanisms:
- **Addition Polymerization:** Involves the addition of monomers with unsaturated bonds (like alkenes) to form a polymer. This can involve intermediates such as carbocations, carbanions, or free radicals.
- **Condensation Polymerization:** Involves the reaction of bifunctional monomers that release a small molecule (like water) during the process.

4. **Dienes and Their Polymerization:**
- Dienes (like isoprene and chloroprene) can undergo a 1,4-addition mechanism, leading to the formation of cis or trans polymers. This type of polymerization is significant in the production of natural rubber.

5. **Properties of Polymers:**
- **Thermoplastics:** These polymers can be heated and reshaped multiple times. Examples include polythene, polystyrene, PVC, and Teflon.
- **Thermosetting Polymers:** These can only be heated once to achieve a specific shape and cannot be reshaped afterward. Examples include Bakelite and Melmac.

6. **Examples of Specific Polymers:**
- **Teflon:** A polymer made from the monomer tetrafluoroethylene, known for its non-stick properties.
- **Polystyrene:** A polymer made from the monomer styrene, commonly used in packaging and insulation.
- **Neoprene:** A synthetic rubber made from the polymerization of chloroprene, used in various applications including wetsuits and gaskets.