聚合物科学作业题.doc

Home Assignments What is the difference in the chain structure of atactic, isotactic, and syndiotactic polystyrene. (Hint: a picture is worth 1000 words!) Which one of these will most likely be incapable of crystallizing? Explain why. ( 20 pts) Explain in clear terms the difference between the addition polymerization and condensation polymerization. Explain your answer with the diagrams/reactions of the examples of both types.( 20 pts) 3. Briefly comment on the difference between the elastic properties of a metal and a rubber band. Explain what gives rise to these differences. ( 20 pts) 4. The values of the solubility parameter, for the certain solvents in (cal/cm3)1/2 are given as follows: Calculate the value of for solutions of polystyrene in these solvents (use a “fudge factor” of 0.34). Indicate which solutions are likely to be single phase and which are likely to be phase-separated. Use Table 11-1 to calculate the solubility parameter of polystyrene from group contributions. Now do the same for poly(butadiene). Note that the solubility parameters of random copolymers can be calculated using (). Calculate the solubility parameter of a 50/50 styrene/butadiene random copolymers. Now calculate the value of for solutions of this copolymers in the solvents listed above. Compare the solubility of polystyrene with that of the random copolymer. (30 pts) 5. As a graduation present, your parents give you the cheap, old clunker of a car that has been sitting in the garage for the last five years. The car is so old that it has flexible vinyl seat coverings (i.e., plasticized PVC). You notice some yellow gunk has built up on the inside of the windshield during this time. Because nobody in your family smokes, you guess that the plasticizer has evaporated out of the PVC and condensed on your windshield. Given that the Tg of pure PVC is about 80,what changes in the stress/strain behavior of your seat coverings would you anticipate over time? What do you think will happen to