Question

Teflon \(^{\otimes}\) is a polymer formed by the polymerization of \(\mathrm{F}_{2} \mathrm{C}=\mathrm{CF}_{2}\). Draw the structure of a section of this polymer. What type of polymerization reaction is required to form it?

Short answer

The structure of a section of the Teflon polymer can be represented as \(\ce{(-CF2-)n}\), where 'n' indicates the repeating monomer units. The polymerization reaction required to form Teflon is addition polymerization or chain-growth polymerization.

Step-by-step solution

Identify the monomer unit and bonds in the polymer

The given polymerization process involves the reaction of \(\mathrm{F}_{2} \mathrm{C}=\mathrm{CF}_{2}\), which represents the monomer required to form the Teflon polymer. The monomer structure has a double bond between the carbon atoms and fluorine atoms bonded to each carbon atom.

Draw the structure of a section of the Teflon polymer

To draw the structure of a section of the Teflon polymer, we need to show the double bond between the carbon atoms breaking and forming single bonds with other monomers. We denote the repeating monomer unit with brackets and subscript 'n', representing that it repeats 'n' times to form the polymer. The section of the Teflon polymer would look like: \[ \mathrm{F}_{2} \mathrm{C} - \mathrm{CF}_{2} -\mathrm{CF}_{2} -\cdots -\mathrm{CF}_{2} \] or more succinctly: \[ \ce{(-CF2-)n} \]

Identify the type of polymerization reaction

The polymerization reaction described involves breaking a double bond in the monomer and forming single bonds with other monomers to create a long chain. This type of polymerization is called "addition polymerization" or "chain-growth polymerization." In conclusion, we have drawn the structure of a section of the Teflon polymer and identified the type of polymerization reaction required to form it as addition polymerization.

Key concepts

Addition Polymerization

Addition polymerization is a type of polymerization in which monomers react to form a polymer without the loss of small molecules, such as water or hydrogen chloride. In this process, monomers with double or triple bonds, known as unsaturated monomers, react together. The double bonds open up and form bonds with other monomers, creating a continuous chain. This is exactly what occurs in the polymerization of Teflon, where the monomer fluorinated ethylene, equation can be written as equates to continues The reaction sequence continues, adding one monomer at a time, until the polymer reaches the desired length.

This process is highly controllable, allowing for the synthesis of polymers with specific lengths, configurations, and properties. The key feature of addition polymerization is that it’s a chain reaction - once initiated, the process continues without the need for additional activation until either the monomer is consumed or a termination step occurs.

Polymer Structure

The structure of a polymer plays a critical role in its physical properties. Polymers consist of long chains of repeating units, called monomers, which are covalently bonded together. The repeating unit in the Teflon polymer is equation If we break down the molecular structure, it consists of a backbone of carbon atoms, with fluorine atoms attached to each carbon. In Teflon, the fluorocarbon chains are highly resistant to chemicals, heat, and electricity due to the strength of the carbon-fluorine bonds. Moreover, the molecular structure of Teflon gives it a high level of crystallinity, contributing to its non-stick properties.

Polymer chains can be linear, branched, or cross-linked, influencing their melting temperature, tensile strength, elasticity, and solubility. The arrangement of the chains can cause polymers to be either amorphous, with a random coil-like structure, or crystalline, with an ordered structure. Teflon, which has a highly crystalline structure, is an excellent example of how a polymer's structure affects its functioning.

Chain-Growth Polymerization

Chain-growth polymerization, also known as chain-reaction polymerization, is another term for addition polymerization that emphasizes the mechanism by which the polymers form. In this process, the growth of polymer chains proceeds through successive addition reactions of monomer molecules, leading to the rapid growth of a polymer chain from its initiating active site.

In the case of Teflon, the monomer tetrafluoroethylene (equation attaches to an initiating active site, typically through a free radical, anionic, or cationic mechanism. Once this initial bond is made, it creates a new reactive site, which allows for the addition of another monomer molecule. This reaction propagates rapidly, with the polymer chain growing in a sequential fashion, adding one monomer unit at a time until the growth is terminated by a combination or disproportionation reaction.

The control of conditions, such as temperature and the concentration of the initiator, allows chemists to govern the molecular weight distribution and the structure of the polymer, optimizing its properties for a wide array of applications.