2006 Exam

Honours Exam 2006: Control of Radical Polymerisation

Time allowed: 24 hours from receipt of exam
Resources allowed: All, but you must cite all resources used in your answers.
Answer all questions.

1. (a) How do the properties of star polymers differ from linear polymers of the same molecular weight? Why? What applications does this make star polymers particularly suitable for? (b) Outline two schemes for producing star polymers of poly(butyl acrylate): one by a ‘core first’ approach and one by an ‘arm first’ approach.

2. “In the paper by Koumura et al. (Macromolecules 39, 12, 4060), Scheme 3 illustrates a process which is likely to be important in the stereoselective polymerisation of vinyl acetate in fluoroalcohol solvents.” Do you agree with this statement? Explain what Koumura et al. are trying to tell us in Scheme 3 and explain why you agree/disagree.

3. A company offers you a large sum of money to produce an electroactive actuator from poly(vinyl acetate). Either (i) explain how you would go about designing such an actuator for them or (ii) explain to them why they should not pursue such an idea.

4. Such, Evans, and Davis (Macromolecules 39, 4, 1391-1396) fit the decolouration of photochromic dyes in a polymer matrix to a biexponential distribution, A(t) = A1e–k1t + A2e–k2t + A∞. From their Table 2, what can you say about the variation in the five fitting parameters in this distribution with the physical properties of the polymer matrix? Do you think there are any good theoretical reasons for fitting the curves to a biexponential rather than a single exponential? Outline any reasons you think of and explain how they are consistent/inconsistent with the experimental data.

5. Fava et al. (Macromolecules 39, 5, 1665-1669) prepared core-shell polymer particles by surfactant-free emulsion polymerisation. Describe this process and what they did. They state that they lightly crosslinked both the core and shell of their particles: does this cast doubt on any of their conclusions? Explain.

6. Tables 1-4 of Osawa et al.’s work on molecularly-imprinted polymers (Macromolecules 39, 7, 2460-2466) present a bewildering mass of data on the binding of substituted amino acids and small peptides by molecularly-imprinted polymers. Prepare an ‘executive summary’ of this information, answering the questions: (i) Have they really achieved anything useful? (ii) What are the most promising ways to extend what they have done in the direction of a useful product?

7. What are the principles of Isothermal Titration Calorimetry (ITC) and how might it be useful? Suggest some control experiments that South et al. (Macromolecules 39, 11, 3738) ought would have carried out as a preliminary to their ITC investigation of small-molecule binding to a complex terpolymer.

8. How would you prepare thermoresponsive magnetic microparticles suitable for use in aqueous solution at temperatures above 60ºC?

9. Predict, with reference to the equations of standard free-radical polymerisation kinetics, if the spatial patterning effects seen by Bryant, Hauch, and Ratner (Macromolecules, 39, 13, 4395 ) could be replicated with a high Tg polymer such as a photo-cured poly(methyl methacrylate). What would you expect to find different/the same in such a system?

10. Assume you have been given (nigh) unlimited resources to devote to the investigation of one current problem involving the control of free radical polymerisation. What problem do you chose to investigate? Outline an experimental plan for your investigations.