“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

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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

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