2008 Exam

CHEM 400 Exam – Advanced Polymer Topics – 2008
Time allowed: 24 hours
Due back: 9 am Monday August 18th 2008
You may use any resource available anywhere in the world, but must cite all resources used.
Answer 10 questions.

Reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene using novel heterocycle-containing chain transfer agents
Rajendran Prakash Babu and Raghavachari Dhamodharan
Polymer International, 57:365–371 (2008)
1. In Figure 9, there are a number of peaks in the 1H NMR which are not assigned, presumably arising from the end-groups derived from the R-group of the RAFT agents.
(a) Assign these peaks.
(b) The mechanism of RAFT polymerization suggests that one additional possible end-group should be observed in each of these three polymers. What is this end-group? Where should peaks arising from it be observed? Can you observe these peaks in the spectra, and is it surprising that you can/cannot?
(c) Are the NMR spectra consistent with the MN values quoted in the caption?

Noncovalent Cross-Linking of Poly(methyl methacrylate) via Polypseudorotaxane
Takayuki Nozaki, Takahiro Uno, Takahito Itoh, and Masataka Kubo
Macromolecules 2008, 41, 5186-5190
2. In this paper…
(a) Why are the products called ‘pseudopolyrotaxanes’ instead of polyrotaxanes? Suggest a procedure for converting them to polyrotaxanes. Can you think of any point in doing this?
(b) Explain what is happening in Figure 5. That is, what is the physical basis for the trend seen in going from prepolymer 1 to prepolymer 5? Is there a way you could present this figure differently to make the trend displayed easier to observe?
(c) How would you expect the dynamic mechanical properties of a pseudopolyrotaxane to differ from a conventional cross-linked polymer and conventional entangled polymer?

Site-Specific Dense Immobilization of Antibody Fragments on Polymer Brushes Supported by Silicone Nanofilaments
Yasuhiko Iwasaki, Yuki Omichi and Ryoko Iwata
Langmuir, doi: 10.1021/la801327a
3. In this work, antibodies are tethered to a surface by random copolymer brushes of 2-methacryloyloxyethy phosphorylcholine (MPC) and glycidyl methacrylate (GMA). What is the advantage of
(a) Tethering the antibodies to brushes, rather than attaching them directly to the surface?
(b) Using these rather complicated monomers in particular, instead of something cheaper?

The Synthesis and Properties of Carbazole-Phenylazomethine Double Layer-Type Dendrimers
Ken Albrecht, Yuto Kasai, Atsushi Kimoto, and Kimihisa Yamamoto
Macromolecules 2008, 41, 3793-3800
4. (a) How does an organic light emitting diode work? Please give diagrams and an explanation that would make sense to a student who had done CHEM 201 and CHEM 202, but no higher level chemistry.
(b) Define all the terms in Figures 6 and 9, and explain the differences in the luminescence vs. voltage curves in terms of the chemical and physical properties of the dendrimers used.

Complementary Hydrogen-Bonded Thermoreversible Polymer
Networks with Tunable Properties
Kamlesh P. Nair, Victor Breedveld and Marcus Weck
Macromolecules 2008, 41, 3429-3438
5. Most publications wishing to demonstrate that controlled polymerization is occurring will include a figure of ‘experimental molecular weight’ vs. ‘theoretical molecular weight’. Construct one of these for the data in Table 1. Does the figure look like it ought to? Why/why not?
6. Pretend you have been given the unenviable task of telling a class of Year Twelve Physics or Chemistry students what Figure 10 means and what information it is telling us about the two polymer networks. Make a Powerpoint presentation (or equivalent: you can draw on the board and take pictures, for instance) of no more than eight slides, writing down on the notes pages (or equivalent) everything you would say exactly as you would say it.

Effect of Molecular Weights of Poly(acrylic acid) on Crystallization of Calcium Carbonate by the Delayed Addition Method
Shu-Chen HUANG, Kensuke NAKA, and Yoshiki CHUJO
Polymer Journal, Vol. 40, No. 2, pp. 154–162, 2008
7. This paper is an examination of how calcium carbonate crystallization can be controlled by co-precipitation of hydrophilic polymers, in a simple model of the very complex process of biomineralisation.
(a) Compare and contrast the results obtained by adding polymer before the onset of crystallization, and after the onset of crystallization. Can you put forward a physical model (with diagrams) for what polyacrylic acid is doing in this system?
(b) One doomsday scenario associated with increasing anthropogenic carbon dioxide emissions is the ‘de-alkalinisation of the oceans’ and the effect this would have on marine life dependent on calcium carbonate. Write an argument using the results of this paper either to hype or downplay (I don’t mind which) this scenario.

Characterization of Oligo(vinyl phosphonate)s by High-Resolution Electrospray Ionization Mass Spectrometry: Implications for the Mechanism of Polymerization
Bahar Bingol, Gene Hart-Smith, Christopher Barner-Kowollik and Gerhard Wegner
Macromolecules 2008, 41, 1634-1639
8. How is the mechanism of polymerization of vinyl phosphonate unusual, according to the findings of this paper?

Nanohybrid Shish-Kebabs: Supercritical CO2-Induced PE Epitaxy on Carbon Nanotubes
Zhiwei Zhang, Qun Xu, Zhimin Chen and Jun Yue
Macromolecules 2008, 41, 2868-2873
9. (a) Discuss the statement: ‘Figure 6 is waaay dodgy.’
(b) During our discussion of this paper, we (well, I guess me, mostly) suggested an alternate explanation for how the observed structures are formed. What experiments could we carry out to see if this explanation or Scheme 2 was more like the truth?
(c) What is epitaxy, anyway? What advantages are there in using a fancy word like this? Are there any simpler words that could do the same job?


Fabrication of “Roll-off” and “Sticky” Superhydrophobic Cellulose Surfaces via Plasma Processing
Balamurali Balu, Victor Breedveld, and Dennis W. Hess
Langmuir 2008, 24, 4785-4790
10. (a) Suggest why the contact angle hysteresis results obtained for the copy paper and the handsheet are different. How could you test this suggestion?
(b) What is XPS? What important information does it reveal in this paper?

Organo-Cobalt Mediated Living Radical Polymerization of Vinyl Acetate
Chi-How Peng, Jennifer Scricco, Shan Li, Michael Fryd, and Bradford B. Wayland
Macromolecules 2008, 41, 2368-2373
11. In Figure 9, the polymerization of vinyl acetate shows no inhibition period. In Figure 10, a marked inhibition period is seen for both vinyl acetate and methyl acrylate.
(a) How does this inhibition period arise?
(b) Why should it be different for methyl acrylate and vinyl acetate?
On the other hand, in Figure 9, retardation in the vinyl acetate polymerization rate is observed in the presence of the cobalt complex.
(c) Can a similar degree of retardation be seen in the polymerizations in Figure 10?
(d) If these polymerizations are significantly more or less retarded than the polymerization in the presence of the cobalt complex in Figure 9, explain why.