1. “Continuous” Emulsifier-Free Emulsion Polymerization
Brian Edwards
McMaster University, Department of Chemistry

2. Contents Introduction Equipment/Polymerization
Particle Growth Mechanism
CEFEP Vs. Multistage Seeding
Conclusions

3. Introduction
Simple alternative for the production of mono-disperse polymeric particles in a wider range of sizes
Larger size mono-disperse particles have been produced by a multistage seeding process, however this is:
Tedious
Difficult to control

4. Polymerization - Equipment
Monomer tank
Water tank
Reactor
Condenser
N2 continuously bubbled through system

5. PS/2% DVB - CEFEP
A nm at 1.5 h
B nm at 6 h

6. PS/2% DVB – Batch/CEFEP
630 nm at 5 h
B m at 14 h

7. PMMA/3 mol % EGDMA – Batch/CEFEP
A.758 nm at 4.5 h
B.1.3 m at 5.5 h

8. CEFEP Amount and timing of initiator is significant
Rate of polymerization & particle size determined by monomer feed rate
Low initiator concentrations function well

9. CEFEP – Contributions To Polydispersity
Later addition of initiator
Excessive initiator
Increase in polymerization temperature

10. CEFEP
Therefore:
Polymerization rate and initiator concentration should be monitored
Add initiator only when a significant decrease in these variables

11. Mechanism of Particle Growth
Oligomeric free radicals:
May terminate - in situ surfactants
May grow – particle precursors & decrease in situ surfactant concentration

12. Mechanism of Particle Growth
CEFEP continues with a core-shell growth mechanism
Monomer feed rate is slow
Polymerization occurs in outer shell

13. Multistage Seeding Process
First stage
B. Second stage

14. Multistage Seeding Process
Third Stage
B. Fourth Stage

15. Multistage Vs. CEFEP Smaller particle size (Direct CEFEP)
Larger particle size, however
Preparation of seed lattice – multistage
Consideration of seed particle concentration – hard to control later in reaction
Phase separation
Secondary nucleation
Smaller particle size (Direct CEFEP)
After particle nucleation, just add monomer
Need to consider monomer and initiator feed rates/amounts

16. Conclusions
Simple
Preliminary batch polymerization can produce quite large particles
Spherical particles with uniform cross-linking
Monodispersity is achieved – simply maintain temperature and monomer/initiator amounts/feed rate

17. References
Li, J.Q. and Salovey, R. J Polym Sci Part A: Polym Chem 2000, 38, 318.
Zou, D., Ma, S., Guan, R., Park, M., Sun, L., Aklonis, J.J. and Salovey, R. J Polym Sci Part A: Polym Chem 1992, 30, 137.
Zou, D., Sun, L. and Aklonis, J.J. J Polym Sci Part A: Polym Chem 1992, 30, 1463.

18. References
4. O’Callaghan, K.J., Paine, A.J. and Rudin, A. J Appl Polym Sci 1995, 58, 2047.
5. Kim, J.H., Chainey, M., El-Aasser, M.S. and Vanderhoff, J.W. J Polym Sci Part A: Polym Chem 1992, 30, 171.
6. O’Callaghan, K.J., Paine, A.J. and Rudin, A. J Polym Sci Part A: Polym Chem 1995, 33, 1849.