Which of the following is a chain-growth polymer?

Options

A. Nylons
B. Polyesters
C. Glycogens
D. Bakelite

Answer

To determine which of the following is a chain-growth polymer, we need to analyze the options provided: Nylon, polyesters, glycogens, and backlight.

### Step-by-Step Solution:

1. **Understanding Polymer Types**:
- There are two main types of polymerization: chain-growth (addition) and step-growth (condensation).
- Chain-growth polymers are formed by the addition of monomers with unsaturated bonds, where the polymer grows by the successive addition of these monomers.
- Step-growth polymers are formed by the reaction of monomers that can react with each other, often resulting in the elimination of small molecules like water.

2. **Analyzing the Options**:
- **Nylon**:
- Nylon (e.g., Nylon 6-6) is produced through condensation polymerization, where water is eliminated during the reaction of diamines and dicarboxylic acids.
- Therefore, Nylon is not a chain-growth polymer.

- **Polyesters**:
- Polyesters, such as Dacron, are also formed through condensation polymerization. They are made from the reaction of diols and dicarboxylic acids, resulting in the elimination of water.
- Hence, polyesters are not chain-growth polymers.

- **Glycogens**:
- Glycogen is a polysaccharide that is formed from the polymerization of glucose units. This process involves the addition of glucose monomers, making it a chain-growth polymer.
- Therefore, glycogen is a chain-growth polymer.

- **Backlight**:
- Backlight is produced from the reaction of phenol and formaldehyde, which also involves the elimination of small molecules (like water), indicating that it is a condensation polymer.
- Thus, backlight is not a chain-growth polymer.

3. **Conclusion**:
- Based on the analysis, the only option that qualifies as a chain-growth polymer is **glycogen**.

### Final Answer:
The correct answer is **glycogen**.