Module 3 Conventional Radical Polymerization

How fast would a radical polymerization proceed? How large the resulting polymers would be?

2 Module objectives

  • Predict how would the polymerization result change when the reaction condition of a radical polymerization is varied.
  • Explain the reason of the change.

3. Classroom implementation ideas

Perform the following simulations and answer the questions.

First, set the default condition as: MA, bulk, AIBN 0.005 mol/L, 60 \(^\circ\)C, 1 h, and run the simulation. Then change one parameter at a time, run the simulation again, and compare to the results from the default condition.

I. Different monomer (MA vs VAc, same molar mass, VAc has smaller \(k_p\))
II. Different monomer concentrations (bulk vs 50%)
III. Different initiator (AIBN vs ACHN) (ACHN decomposition is much slower)
IV. Different initiator concentrations (0.005 vs 0.01 mol/L)
V. Different temperatures (60 \(^\circ\)C vs 80 \(^\circ\)C)

For every single reaction answer this question:

  1. Compare the number of polymers obtained from the polymerization and the number of initiator consumption
    A. much greater; B. comparable (ratio within 0.5 to 2 and keep constant); C. much less

For each pair of reactions answer the following questions (the second reaction compare to the first reaction).

  1. Radical concentration
    A. increase; B. similar; C. decrease; D. need more information to tell

  2. Rate of polymerization (i.e. percent consumption of monomers vs time)
    A. increase; B. similar; C. decrease; D. need more information to tell

  3. Reason for the change in polymerization rate (the answer could be one or both of the choices)
    A. change in radical concentration; B. change in \(k_p\)

  4. Explain your choices for the above two questions.

  5. Initial molecular weight
    A. increase; B. similar; C. decrease; D. need more information to tell

  6. Reason for the change in initial molecular weight (the answer could be one or multiple of the choices)
    A. rate of monomer consumption; B. monomer concentration; C. number of polymers being formed.

  7. Explain your choices for the above two questions.

4. Example practice questions

  1. In a conventional radical polymerization, adding more thermal initiator, e.g., AIBN, and keeping all other reaction conditions not changed, what would happen to the product?
  1. More polymers will be produced at the same reaction time.
  2. Higher monomer conversion is expected at the same reaction time.
  3. Lager average molecular weight is expected.
  4. Higher radical concentration is expected at the same reaction time.
  1. In a conventional radical polymerization, change the initial monomer concentration from 8 mol/L to 4 mol/L (by changing the ratio between the monomer and inert solvent) and keep all other reaction conditions not changed, what would happen to the product?
  1. Fewer polymers will be produced at the same reaction time.
  2. Lower monomer conversion is expected at the same reaction time.
  3. Lower average molecular weight is expected.
  4. Lower radical concentration is expected at the same reaction time.