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.

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 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 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.