Purpose:

Reaction kinetics are measured for solution polymerization of methyl methacrylate in a batch reactor. This experimental station demonstrates that variables other than concentration can be used to measure kinetic parameters and examines how variables including initiator concentration and solvent can impact polymer molecular weight.

The parameters that can be varied are:

• temperature
  
• relative concentrations of solvent and methyl methacrylate
  
• initiator concentration/type of initiator

• solvent type

• monomer type

• effective reaction orders for a free radical chain reaction
  
• temperature dependence of an overall rate constant
  
• initiation delay due to radical buildup
  
• chain transfer to solvent
  
• molecular weight dependence on initiator concentration, chain transfer

Kinetics of Polymerization:

Experimental Setup:

Polymerization in a dilatometer allows measurement of the volume change with time as the lower-density monomer reacts to form a higher-density polymer. Monomer, initiator, and solvent are individually measured by weight and mixed. Approximately 100 ml of the mixture is drawn by vacuum into a dilatometer, filling it completely. The dilatometer (except for the protruding capillary) then is immersed into a preheated constant-temperature water bath. Expansion forces some of the mixture out as it and the dilatometer warm to the bath temperature, and after some delay, the volume begins to decrease due to reaction. Volume is measured as a function of time with a cathetometer, measuring the height of the meniscus in the capillary. Molecular weight is determined by measuring the height change in the dilatometer through the use a cathometer. The chemicals used include methyl methacrylate (monomer), benzoyl peroxide (initiator), ethyl acetate (solvent), and acetone (cleaning solvent).

Notes:

• Refer to section "Documentation and Manuals" below for more information on this experimental station and for references involving polymerization. Fogler contains a section on polymerization, and you may need to refer to other literature to derive the appropriate equations for the determination of reaction rate order and activation energy. There is a document accessible via the course website that details polymerization kinetics.
  
• This experimental station has numerous safety hazards associated with it – pay particular attention when preparing your preliminary presentation and methodology for conducting your proposed experiments. Pay particular attention to hazardous waste handling and disposal.
  
• The temperature bath should be set in the morning to the correct temperature so that you will be ready to perform experiments in the afternoon – ask the laboratory staff to do this for you ahead of time

2. Another protocol for polymerization of MMA using AIBN (GPC instructions included)

3. GPC basics

4. Benzoyl Peroxide Material Safety Data Sheet (MSDS)

5. Benzoyl Peroxide Handling and purification (ONLY IF NEEDED, PROCEED WITH CAUTION)

6. Chain Growth Polymerization

7. Calculating PDI

8. Determination of Chain Transfer Coefficient (Research paper)