The polymer obtained with a methylene bridges by condensation polymerisation is:

Options

A. PVC
B. Buna-S
C. Polyacrylonitrile
D. Bakelite

Explanation

To solve the question regarding the polymer obtained with methylene bridges by condensation polymerization, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Condensation Polymerization**:
- Condensation polymerization is a type of polymerization where monomers join together with the elimination of small molecules, typically water. This process is also known as step-growth polymerization.

2. **Identify the Role of Methylene Bridges**:
- Methylene bridges refer to the -CH2- groups that connect different parts of the polymer chain. This is crucial for identifying the correct polymer.

3. **Examine Various Polymers**:
- **Polyvinyl Chloride (PVC)**: Formed by addition polymerization, does not contain methylene bridges.
- **Buna S**: A copolymer formed from two different monomers, does not have methylene bridges.
- **Polyacrylonitrile**: Also formed by addition polymerization, lacks methylene bridges.

4. **Identify the Correct Polymer**:
- **Bakelite**: This is a well-known polymer formed by the condensation polymerization of phenol and formaldehyde. In its structure, it contains methylene bridges (-CH2-), which connect phenolic units.

5. **Illustrate the Structure of Bakelite**:
- The structure of Bakelite includes multiple phenolic rings connected by methylene bridges. It can be represented as follows:
- The repeating unit consists of phenol (C6H5OH) and formaldehyde (CH2O), resulting in a network structure with -CH2- links.

6. **Conclusion**:
- Based on the analysis, the polymer obtained with methylene bridges by condensation polymerization is **Bakelite**.

### Final Answer:
The polymer obtained with methylene bridges by condensation polymerization is **Bakelite**.