Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 28: Problem 672

When formaldehyde is polymerized to a linear polymer in heptane solvent, with \(\left(\mathrm{C}_{6} \mathrm{H}_{5}\right){ }_{3} \mathrm{P}\) or a proton as a catalyst, it yields a thermally unstable material (A) that unzips readily to re-form formaldehyde. However, if the end of the polymer is 'capped", the product is a highly crystalline, tough polymer. The example below, \(\mathrm{B}\), is called Delrin and is already replacing nylon as a molding resin. Suggest a reason for the stability gained by capping the polymer.

Short Answer

Expert verified
The increased stability gained by capping the polymer is due to the prevention of the unzipping process. Capping the ends of the polymer chain involves chemically modifying them, making it more challenging for the polymer to unzip under thermal or mechanical stress. This modification can create stronger intermolecular forces and prevent the ends of the polymer chain from breaking as easily, resulting in a more stable and durable material than the uncapped version.

Step by step solution

01

Understand the polymerization process and its catalysts

In the given exercise, formaldehyde is polymerized to form a linear polymer. The catalysts involved in this process are either \(\left(\mathrm{C}_{6} \mathrm{H}_{5}\right){ }_{3} \mathrm{P}\) or a proton. The synthesized polymer is thermally unstable and can easily unzip to re-form formaldehyde. This unstable polymer is denoted as (A).
02

The effect of capping the end of the polymer

When the ends of polymer A are capped, the product becomes a highly crystalline, tough polymer called Delrin (denoted as B). The capping process involves chemically modifying the ends of the polymer chain to prevent them from unzipping. Capping increases the stability of the polymer.
03

Suggest a reason for the increased stability due to capping

The reason for the increased stability gained by capping the polymer can be related to the prevention of the unzipping process. When the polymer chain is uncapped, the polymer can easily unzip due to thermal or mechanical stress, leading to a quick decomposition back to formaldehyde. However, when the ends of the polymer are capped, they are chemically modified, making the unzipping process more challenging. This modification can create stronger intermolecular forces and prevent the ends of the polymer chain from breaking as easily. Thus, the capped polymer remains stable and does not rapidly decompose, making it a more stable and durable material than the uncapped version.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Apparently the economically important chain reaction, wool \(+\) moths \(\rightarrow\) holes \(+\) more moths, has, as a key step, scission of the disulfide linkages of cystine in the polypeptide chains by the digestive enzymes of the moth larva. Devise a method of mothproofing wool which would involve chemically altering the disulfide linkages

The rate of free-radical polymerization of styrene, induced by benzoyl peroxide in mixtures of carbon tetrachloride and benzene, is independent of the concentration of carbon tetrachloride. At high concentrations of carbon tetrachloride, the average molecular weight of the polymer is greatly reduced and chlorine is found in the polymer. Explain.

Natural rubber is attacked readily by ozone. If the resulting material is treated with \(\mathrm{H}_{2} \mathrm{O}_{2}\) in acetic acid, the major product isolated is levulinic acid \(\left(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{3}\right)\). (a) What is the structure of levulinic acid? (b) If a rubber plant is fed radioactive sodium acetate labeled only at the acetate methyl \(\left({ }^{*} \mathrm{CH}_{3} \mathrm{CO}^{-}{ }_{2} \mathrm{Na}^{+}\right)\), radioactive rubber can be obtained from the latex of the plant after a short time. Degradation of this rubber by ozone yields radioactive levulinic acid. Which specific carbon atoms of the levulinic acid would you expect to be radioactive?

Give an example of coordination polymerization. Name the chemists responsible for the discovery of this method of polymerization.

Show how the successive use of cation- and anionexchange resins could be used to remove sodium chloride from water.
See all solutions

Recommended explanations on Chemistry Textbooks

The Earths Atmosphere

Read Explanation

Chemical Analysis

Read Explanation

Inorganic Chemistry

Read Explanation

Ionic and Molecular Compounds

Read Explanation

Kinetics

Read Explanation

Organic Chemistry

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free