Question

Draw the structure of the monomer and the basic repeating unit for each of the following polymeric substances. a. polyethylene b. polyvinyl chloride c. Teflon d. polypropylene e. polystyrene

Short answer

a. Ethylene monomer: \( H_2C=CH_2 \), Polyethylene repeating unit: \(-CH_2CH_2-\) b. Vinyl chloride monomer: \( CH_2=CHCl \), Polyvinyl chloride repeating unit: \(-CH_2CHCl-\) c. Tetrafluoroethylene monomer: \( CF_2=CF_2 \), Teflon repeating unit: \(-CF_2CF_2-\) d. Propylene monomer: \( CH_2=CHCH_3 \), Polypropylene repeating unit: \(-CH(CH_3)CH_2-\) e. Styrene monomer: \( C_6H_5CH=CH_2 \), Polystyrene repeating unit: \(-C_6H_5CHCH_2-\)

Step-by-step solution

Identifying the monomers for each polymer

The first step is to identify the monomers for each of the polymeric substances listed. Here are the monomers for each polymer: a. Polyethylene: Ethylene b. Polyvinyl chloride: Vinyl chloride c. Teflon: Tetrafluoroethylene d. Polypropylene: Propylene e. Polystyrene: Styrene

Drawing the monomer structures

Based on the monomers identified in Step 1, we will now draw the structures of each monomer. a. Ethylene: \( H_2C=CH_2 \) b. Vinyl chloride: \( CH_2=CHCl \) c. Tetrafluoroethylene: \( CF_2=CF_2 \) d. Propylene: \( CH_2=CHCH_3 \) e. Styrene: \( C_6H_5CH=CH_2 \)

Drawing the basic repeating units for each polymer

Now, we will draw the basic repeating units for each polymer. This involves converting the double bond in the monomer structure to a single bond and attaching it to the next monomer unit. a. Polyethylene: \(-CH_2CH_2-\) b. Polyvinyl chloride: \(-CH_2CHCl-\) c. Teflon: \(-CF_2CF_2-\) d. Polypropylene: \(-CH(CH_3)CH_2-\) e. Polystyrene: \(-C_6H_5CHCH_2-\) Each of these structures represents the basic repeating unit of the respective polymer, and when repeated several times, they form the polymer chain. Note that the dashes at the beginning and end of each structure indicate the connection to the neighboring repeating units in the polymer chain.

Key concepts

Monomer Identification

Understanding the building blocks of polymers starts with monomer identification. Monomers are the smallest units in a polymer that can be repeated to form the larger polymer chain. Each monomer has a specific structure and set of characteristics that determine the properties of the final polymer.

For example, the monomer for polyethylene is ethylene, which is a small hydrocarbon molecule with the chemical formula of ( H_2C=CH_2 ). Recognizing the various monomers, like vinyl chloride for polyvinyl chloride or styrene for polystyrene, is crucial because the monomer type dictates the polymer's physical and chemical properties.

When identifying monomers, look for patterns such as the presence of double bonds, characteristic functional groups (such as a chlorine atom in polyvinyl chloride), and their position within the molecule. Understanding these patterns is essential for comprehending the macromolecular structure of polymers.

Chemical Structure Representation

The chemical structure representation of a molecule is a visual way to express the arrangement of atoms within it. These representations are critical when discussing polymers because they lay the groundwork for understanding how monomers connect to form polymer chains.

A chemical structure can be represented in various formats such as Lewis structures, space-filling models, or skeletal formulas. For instance, in the skeletal formula, bonds between carbon atoms are depicted as lines, and hydrogen atoms are often omitted for clarity. In polymers, this method streamlines the depiction of repeating units.

Skeletal Structures and Polymer Chains

When drawing the structures of polymers, it is essential to convert the double bonds of the monomers into single bonds that join them together. This transformation signifies the chemical reactions that occur during polymerization. The dash at each end of the repeating unit represents the bond to the next unit in the polymer chain, emphasizing the continuous nature of polymers.

Polymer Chain

A polymer chain is a long, repeating sequence of monomers linked by covalent bonds. These chains can vary greatly in length, with some consisting of thousands of monomers. The process of forming a polymer chain from monomers is known as polymerization. During this chemical reaction, monomers are joined by breaking double bonds and forming single bonds with neighboring monomers.

The structure of the polymer chain determines much of the material's properties, such as elasticity, toughness, and melting point. For example, the repeating units in polyethylene, (-CH_2CH_2-), create a flexible and sturdy material ideal for a wide range of applications.

Different types of polymer chains exist, including linear, branched, or cross-linked, which further influence the mechanical and thermal behavior of the polymer. Recognizing these models is key to understanding polymer science and engineering, as well as predicting how a polymer will behave in real-world applications.