CHEMISTRY 410NAME: ______

EXAM ONE

OCTOBER 3, 2005

DR. KOPITZKE

INSTRUCTIONS

1. This exam has 7 pages including this cover sheet. Make sure that your test has all of these pages.

2. The exam will be graded out of 100 pts. Point values for the questions are included with each question.

3. Put your name of the first page. Do not put it on other pages.

4. You may use a calculator and a periodic table for this exam.

SUGGESTIONS

1. Pace yourself. Don’t spend too much time on one question.

2. Relax. Look through the entire test first. Do some problems that you know very well.

3. If a question seems unclear, don’t guess, ask!

USEFUL FORMULAS:

Solubility parameter = dΣG

M

1. Provide concise definitions or explanations for five of the following (3 pts each)

a. degree of polymerization

b. morphology

c. injection molding

d. block copolymer

e. network polymer

f. chain-growth kinetics

g. hydrodynamic volume

2.) Provide the correct choice and a rationale for the following questions. (5 pts each)


a.) Which polymer would have the highest Tg? What is your rationale?


b.) Which polymer would be most crystalline? What is your rationale?

c.) Which polymer would have the highest Tg. What is your rationale?

3. Explain why a stretched rubber-band contracts upon heating. (5 pts)

4. How and why does the glass-transition temperature vary with molecular weight? (5 pts)

5. Answer five of the following (8 pts each).

a) What is the difference between absolute and relative methods of molecular weight determination? Give an example of each.

b.) Draw (3-D drawings) isotactic and atactic polypropylene (show at least 5 repeat units). How would the physical and/or mechanical properties of these two polymers differ (give a couple of examples)?

c.) What is the difference between a thermoplastic and a thermosetting plastic both in terms of properties and in terms of chain structure.

d.) Explain how the crystal structure of semicrystalline polymers will vary if the molten polymer is allowed to crystallize undisturbed (e.g. in a mold) versus if the molten polymer is drawn into a fiber.

e.) Define modulous and explain how the modulous of a semi-crystalline plastic would vary with temperature.

f.) What is GPC? Explain how the technique works (general principles) and how molecular weight data is obtained using this technique (including what specific data is obtained).

g. In class, we learned about two methods for determining Tg, DSC (differential calorimetry) and DMTA (dynamic mechanical thermal analysis). What polymer properties are actually being measured by each of these instruments and how do these properties change at the glass-transition temperature?

4.) Determine the number average molecular weight, the weight average molecular weight and the polydispersity index for the following sample: (12 pts)

5 moles @ 100 amu

10 moles @ 20000 amu

10 moles @ 30000 amu

5. One gram of a polymer with a degree of polymerization of 100 required 8.85 ml of 0.010 M NaOH to titrate its acid end-groups. What is the weight of the repeat unit of the polymer to the nearest whole number? (8 pts)