Indicate the correct statement for chain growth polymers

Options

A. These polymers are made by the addition of monomers
B. The end of a chain is reactive because it is a free radical cation or anion
C. Polystyrene is the example of this class
D. It takes place step by step

Explanation

To determine the correct statement for chain growth polymers, let's analyze the options provided step by step.

### Step 1: Understanding Chain Growth Polymers
Chain growth polymers, also known as addition polymers, are formed through the addition of monomers. This process involves the repeated addition of monomer units to the growing chain, leading to the formation of long polymer chains.

**Hint:** Remember that chain growth polymers are formed by adding monomers to the end of a growing chain.

### Step 2: Analyzing the Reactivity of the Chain End
The end of a chain growth polymer is reactive due to the presence of free radicals, cations, or anions. This reactivity is essential for the continuation of the polymerization process, as it allows for further monomer addition.

**Hint:** The reactivity at the chain end is crucial for the polymerization process.

### Step 3: Identifying Examples of Chain Growth Polymers
Polystyrene is a well-known example of a chain growth polymer. It is synthesized through the polymerization of styrene monomers. This example helps illustrate the concept of chain growth polymers.

**Hint:** Look for common examples of chain growth polymers to solidify your understanding.

### Step 4: Evaluating the Statements
Now, let's evaluate the statements provided in the question:

1. **These polymers are made by the addition of monomer.**
- This statement is correct. Chain growth polymers are indeed formed by the addition of monomers.

2. **The end of the chain is reactive because it is a free radical cation or anion.**
- This statement is partially correct. The end of the chain is reactive because it can be a free radical, cation, or anion, but it is not limited to just free radicals.

3. **Polystyrene is the example of this class and it takes place step by step.**
- This statement is incorrect. While polystyrene is an example of a chain growth polymer, the process does not occur "step by step" as in step-growth polymerization; it occurs through a continuous addition of monomers.

### Conclusion
The correct statement for chain growth polymers is:
- **These polymers are made by the addition of monomer.**