Question

Polystyrene can be made more rigid by copolymerizing styrene with divinylbenzene: How does the divinylbenzene make the copolymer more rigid?

Short answer

Divinylbenzene makes the copolymer more rigid by acting as a cross-linking agent, creating multiple bonds between the styrene and divinylbenzene chains. These cross-links restrict the movement of the chains, resulting in a more stable and rigid structure.

Step-by-step solution

Explain the process of Polymerization

Polymerization is the process of linking monomers to form a polymer. In the case of styrene, a chain of styrene molecules is bonded together to create polystyrene, a plastic used in a wide range of applications. During polymerization, the double bond between the carbon atoms in styrene breaks and forms single bonds with other styrene molecules, creating the polymer chain.

Define Copolymer

A copolymer is a polymer derived from two (or more) monomeric species. In this case, styrene and divinylbenzene are the two monomeric species which form the copolymer.

Describe the Structure of Divinylbenzene

Divinylbenzene consists of a benzene ring with two vinyl groups (-CH=CH2). In copolymerization, divinylbenzene serves as a cross-linking agent; in other words, it helps in creating bridges or links between different polymer chains.

Explain Cross-Linking and Rigidity

The cross-links between the chains restrict the movement of the chains, making the plastic more rigid. The most effective cross-linking agents are multifunctional monomers, that is, possess more than one bonding site. They bond with other monomers at several points, creating cross-links. Divinylbenzene, with the two vinyl groups, does exactly that in the copolymerization with styrene. By creating these cross-links, it makes the overall structure more stable and rigid.

Conclude

Hence, the reason divinylbenzene makes the copolymer more rigid is due to it acting as a cross-linking agent. By creating multiple bonds and restricting the movement of the polymer chains, it increases the rigidity of the final product.

Key concepts

Copolymerization

Copolymerization is a type of polymerization where two or more different types of monomers are combined to form a copolymer. This process enhances the properties of the resulting material and can be tailored to specific needs. In the example of creating more rigid polystyrene, copolymerization involves the use of styrene and divinylbenzene. Styrene provides the core properties of polystyrene, while divinylbenzene introduces cross-links that enhance rigidity.

When styrene is copolymerized with divinylbenzene, the resulting polymer gains the combined properties of both monomers. This leads to a material with an adaptability that pure polystyrene lacks. For instance, the thermal resistance, chemical stability, or mechanical strength can be improved. This ability to fine-tune polymers through copolymerization is what makes it a fundamental concept in materials science.

Divinylbenzene

Divinylbenzene is a crucial cross-linking monomer used in copolymerization processes due to its two vinyl groups attached to a single benzene ring. Each vinyl group contains a double bond that can react with styrene. The structure of divinylbenzene allows it to act as a bridge between two or more polymer chains, joining them together through the process of cross-linking.

This cross-linking capacity is what can turn a standard polymer like polystyrene into a more rigid and durable material. Divinylbenzene's ability to multilaterally connect different polymer strands adds dimensional stability and strength, making it an important monomer in producing industrial polymers, where enhanced material properties are often required.

Polystyrene

Polystyrene is a versatile and widely used plastic that can be found in many everyday products, from packaging materials to insulation. It is composed of the monomer styrene, which, when polymerized, forms long chains that can be rigid or foamed.

While polystyrene in its basic form has many advantageous properties like light weight and ease of molding, it lacks in other areas such as rigidity and structural strength. However, by copolymerizing styrene with divinylbenzene, polystyrene's characteristics can be significantly improved, making it suitable for a broader range of applications that require materials with greater mechanical stability.

Cross-Linking

Cross-linking is a chemical process that connects two or more polymer chains together via bonds. These connections can be achieved through various types of chemical reactions but often involve the use of multifunctional monomers like divinylbenzene in the case of copolymerization.

When cross-linking occurs, the movement of the polymer chains is greatly restricted because they are no longer able to slide past each other with ease. This resulting network of linked chains enhances many physical properties of the material, including its rigidity, heat resistance, and chemical resistance. Cross-linking is essential in creating durable polymers for high-performance applications, such as in automotive parts, medical devices, and construction materials.

Polymer Rigidity

Polymer rigidity refers to the hardness and stiffness of a polymer material, preventing deformation under stress. The rigidity of a polymer is tremendously important in applications where dimensional stability and the ability to bear load without bending are required.

Increasing the rigidity of a polymer like polystyrene typically involves the addition of cross-links, which reduce the flexibility of the polymer chains. Chemicals like divinylbenzene introduce these cross-links, effectively transforming a flexible and moldable plastic into a much more rigid one. This allows for the creation of polymers that can be used in a wider array of applications and environments, significantly extending the versatility and usefulness of the base polymer.