26.07.2021 Views

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

General Chemistry Principles, Patterns, and Applications, 2011

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

9. A<br />

polymerization reaction is used to synthesize Saran, a flexible material used in packaging<br />

film <strong>and</strong> seat covers. The monomeric unit for Saran is 1,1-dichloroethylene (CH 2 =CCl 2 ), also<br />

known as vinylidene chloride. Draw a reasonable structure for the polymer. Why do pieces<br />

of Saran “cling” to one another when they are brought in contact?<br />

8. Polymers are often amorphous solids. Like other materials, polymers can also undergo phase changes. For<br />

example, many polymers are flexible above a certain temperature, called the glass-transition<br />

temperature (T g ). Below the glass transition temperature, the polymer becomes hard <strong>and</strong> brittle. Biomedical<br />

devices that replace or augment parts of the human body often contain a wide variety of materials whose<br />

properties must be carefully controlled.<br />

a. Polydimethylsiloxane has a T g of −123°C, whereas poly(methylmethacrylate) has aT g of<br />

105°C. Which of these polymers is likely to be used in dentures, <strong>and</strong> which is likely to be<br />

used for soft-tissue replacement?<br />

b. If you were designing biomedical devices, which class of biomaterials (alloys, ceramics, or<br />

polymers) would you consider for finger joint replacements, eyeball replacements,<br />

windpipe replacements, shoulder joint replacements, <strong>and</strong> bridging bone fractures? Explain<br />

your answers.<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

1170

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!