Post on 17-Jan-2016
“Continuous” Emulsifier-Free Emulsion Polymerization
Brian EdwardsMcMaster University, Department of Chemistry
ContentsIntroductionEquipment/PolymerizationParticle Growth MechanismCEFEP Vs. Multistage SeedingConclusions
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
Polymerization - Equipment
Monomer tank Water tank Reactor Condenser N2
continuously bubbled through system
PS/2% DVB - CEFEP
A. 284 nm at 1.5 h
B. 442 nm at 6 h
PS/2% DVB – Batch/CEFEP
630 nm at 5 h
B. 1.9 m at 14 h
PMMA/3 mol % EGDMA – Batch/CEFEP
A.758 nm at 4.5 h
B.1.3 m at 5.5 h
CEFEP Amount and timing of initiator is
significant Rate of polymerization & particle size
determined by monomer feed rate Low initiator concentrations function
well
CEFEP – Contributions To Polydispersity
Later addition of initiatorExcessive initiatorIncrease in polymerization
temperature
CEFEPTherefore: Polymerization rate and initiator
concentration should be monitored Add initiator only when a
significant decrease in these variables
Mechanism of Particle Growth
Oligomeric free radicals: May terminate - in situ surfactants May grow – particle precursors &
decrease in situ surfactant concentration
Mechanism of Particle Growth
CEFEP continues with a core-shell growth mechanism
Monomer feed rate is slowPolymerization occurs in
outer shell
Multistage Seeding Process
First stage
B. Second stage
Multistage Seeding Process
Third Stage
B. Fourth Stage
Multistage Vs. 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
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
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.
References4. 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.