When styrene (vinylbenzene) is commercially polymerized, about 1–3% of 1,4-divinylbenzene is often added to the styrene. The incorporation of some divinylbenzene gives a polymer with more strength and better resistance to organic solvents. Explain how a very small amount of divinylbenzene has a marked effect on the properties of the polymer.

Verified step by step guidance

1. Step 1: Understand the structure of styrene and 1,4-divinylbenzene. Styrene (vinylbenzene) has a benzene ring with a single vinyl group (-CH=CH2) attached. 1,4-divinylbenzene has a benzene ring with two vinyl groups attached at the 1 and 4 positions.
2. Step 2: Recognize the role of 1,4-divinylbenzene in polymerization. During polymerization, the vinyl groups in styrene undergo a chain-growth polymerization to form long polymer chains. The presence of 1,4-divinylbenzene introduces additional vinyl groups that can form cross-links between different polymer chains.
3. Step 3: Explain the concept of cross-linking. Cross-linking occurs when the vinyl groups on 1,4-divinylbenzene react with the growing polymer chains, creating covalent bonds between separate chains. This results in a three-dimensional network structure rather than linear polymer chains.
4. Step 4: Discuss the impact of cross-linking on polymer properties. The cross-linked structure restricts the movement of polymer chains, making the material more rigid and less prone to deformation. This enhances the strength and resistance to organic solvents of the polymer.
5. Step 5: Conclude by emphasizing the significance of small amounts of 1,4-divinylbenzene. Even a small percentage of 1,4-divinylbenzene can create enough cross-links to significantly alter the polymer's mechanical and chemical properties, leading to improved performance in commercial applications.

Key Concepts

Polymerization

Polymerization is the chemical process in which small molecules, known as monomers, combine to form a larger, more complex structure called a polymer. In the case of styrene, the polymerization process leads to the formation of polystyrene, a widely used plastic. The addition of a cross-linking agent like divinylbenzene during polymerization can significantly alter the physical properties of the resulting polymer.

Cross-linking

Cross-linking refers to the formation of chemical bonds between polymer chains, which can enhance the strength and stability of the material. When divinylbenzene is added to styrene, it acts as a cross-linker, creating connections between polystyrene chains. This results in a three-dimensional network structure that improves the mechanical properties and solvent resistance of the polymer.

Thermal and Chemical Resistance

Thermal and chemical resistance are critical properties of polymers that determine their performance in various environments. The incorporation of divinylbenzene into the polymer matrix increases the density of cross-links, which enhances the material's ability to withstand heat and exposure to organic solvents. This makes the modified polymer more durable and suitable for applications requiring higher performance under challenging conditions.