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Individual Assignments Problem Set #1 1. (a) Draw the repeating unit structures of the polymers obtained from the following monomers: (b) III & HS SH (a) (c) + N O Il (d) HO OH + CI (e) H2N COOH CI o (b) Which of the polymerizations mechanisms, step-growth, chain-growth or ring-opening, are appropriate for the synthesis of these polymers? (c) Show all significant bi-products that are formed (if any) in the polymerizations. (d) For the polymers synthesized by step-growth mechanisms, state whether they are condensation or addition polymers. 2. (a) By means of chemical reactions schemes, show how polymers with the repeat unit structures shown below may be synthesized. Draw the structures of the monomer or monomers that may be used and briefly describe the types of chemical reactions involved. Consider alternative monomer(s) and synthetic methods where applicable and comment on the pros and cons of the different methods where appropriate. (a) lofgect (b) poloto (c) HI. (d) that (e) gergian 3. A sample of a polymer is composed of the following fractions of different sized molecules: Weight fraction Molecular weight (kg/mole) 0.09 10 0.20 20 0.25 35 0.18 50 0.11 75 0.07 100 0.06 125 0.04 150 Calculate (a) the number average degree of polymerization; (b) the weight average degree of polymerization and (c) the molecular weight dispersity of the sample. Draw a mass distribution chart for the sample and mark the position of the molecular weight averages on the chart. 4. (a) Calculate the number average degree of polymerization (Xn) for an equimolar mixture of sebacic acid and ethylene glycol for extents of reaction 0.500, 0.800, 0.850, 0.900, 0.950, 0.970 and 0.990 and 0.995. Plot the extent of reaction (x-axis) against Xn (y-axis) and comment on the consequences of the result in step-polymerizations. (b) What is the number average molecular weight of the polymer sample when the extent of reaction is 0.995? The structures, molecular formulae and molecular weights of the monomers are as follows: COOH OH HOOC HO Sebacic acid (C,10H18O4) Ethylene glycol (CgH14O4 MW 202 g/mole MW 150 g/mole 5. In a free radical polymerization that proceeds without chain transfer, what is the effect of (a) increasing the monomer concentration [M] by a factor of four at constant initiator concentration and (b) increasing the initiator concentration [U] by a factor of four at constant monomer concentration on each of the following: (i) the total radical concentration at steady state ([M-]) (ii) the rate of polymerization (Rp) (iii) the number average degree of polymerization (Xn)? Explain your answers.

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