Sample questions: Sketches

1. Sketch an apparatus (including light source, sample, and detector, with each labelled) that can measure the frequency of the stretching of the C=C bond in poly(2,3-dimethylbutadiene).

2. Sketch the Morse potential. In comparison with the potential for the harmonic oscillator, state one way in which the two potentials are similar, and one way in which they are different.

3. Explain, with the aid of an appropriately labelled sketch, the temperature dependence of the intensity and shape of the Amide I band for a semicrystalline nylon.

4. Explain, with the aid of an appropriately labelled sketch, how infrared spectra at 1650-1800 cm^-1 can be used to determine if blends of poly(4-vinylphenol) and poly(vinyl acetate) are intimately mixed.

5. With the aid of an appropriate Jablonski diagram, describe (a) Why fluorescence emission occurs at longer wavelength than excitation, and (b) The origin of vibrational spacing observed in an emission spectrum.

6. In dilute solution, polystyrene exhibits an absorption band near 260 nm and two emission bands at about 280 nm and 340 nm. Draw and label a Jablonski diagram that depicts the transitions involved in these three bands.

7. Sketch the efficiency of nonradiative singlet energy transfer as a function of the separation of the donor and acceptor. Show the position of the Forster radius on your sketch.

8. Sketch an apparatus (including positions of light source, sample and detector, with each labelled) that can measure the excimer fluorescence in polystyrene.

9. Sketch the CD spectra of a synthetic polypeptide, such as poly(L-lysine), as a random coil and as an alpha helix. Label the axes of the sketch.

10. Sketch the Lennard-Jones potential energy function, showing epsilon and sigma.

11. Sketch the population vs. phi for the internal C-C bond in n-butane at 300 K. Define your choice of phi = 0.

12. On the same diagram, sketch the V vs. T behavior at constant P for a small molecule as it is cooled from the gas to a (a) crystal and (b) glass. Label all physical processes in the sketch.

13. Sketch on the same plot the normalized radial distribution function (called W(R) in the text) for two Gaussian chains, where one chain has four times as many bonds as the other. Pay close attention to the relative scales for the two curves. Label the sketch.

14. Sketch and describe the structure formed by a polystyrene-poly(ethylene oxide) diblock copolymer when in dilute solution (0.1% by weight) in methanol.

15. Sketch the behavior of the second virial coefficient for a polymeric hydrocarbon (such as polyisobutylene) in a nonpolar solvent (such as benzene) over a range of temperature that includes the Theta temperature. Label the sketch.

16. The unit cell of orthorhomic polyethylene has a = 0.740 nm, b = 0.493 nm, and c = 0.2534 nm. Sketch the appearance of one chain and its immediate neighbors when the system is viewed along the c axis.

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