1. Heterogeneous Polymerizations
Distinguished by:
Initial state of the polymerization mixture
Kinetics of polymerization
Mechanism of particle formation
Shape and size of the final polymer particles
Precipitation
Suspension
Dispersion
Emulsion

2. Free Radical Polymerizations
0.01
0.1 1 10
100
Particle Size
(µm)
Precipitation
Solution
Emulsion
Dispersion
Suspension
Medium
solvency
monomer: insoluble
polymer : insoluble
soluble
insoluble
soluble

3. Precipitation Polymerization
Solvent M I hν or Δ P
Solvent, monomer & initiator
Polymer becomes insoluble in the solvent (dependent on MW, crystallinity, rate of polymerization
Polymerization continues after precipitation (?)

4. Precipitation Polymerization
Considerations:
Ease of separation
Used for:
Vinyl chloride (solvent free)
Poly(acrylonitrile) in water
Fluoroolefins in CO2
Poly(acrylic acid) in benzene
Poly(acrylic acid) in CO2
Traditionally, not too applicable…
Rule of thumb, polymer must be insoluble in its own monomer…

5. Conventional Polymerization of Fluoroolefins
Aqueous Emulsion or Suspension
Non-aqueous Grades
Uses water
Needs surfactants (PFOS / PFOA / “C-8”)
Ionic end-groups
Multi-step clean-up
Uses CFCs & alternatives
Surfactant free
Stable end-groups
Electronic grades

6. Polymerization of Fluoroolefins in CO2
Teflon PFA™, FEP™
Tefzel™
PVDF
Nafion™
Kalrez™
Viton™
Typical Reaction
10-50% solids
°C (batch)
Pressures bar at 35 °C
End group analysis (FTIR) shows 3 COOH, COF end groups per 106 carbons
<Mn> ~ 106 g/mol without chain transfer agent
Romack, T. J.; DeSimone, J.M. Macromolecules 1995, 28, 8429.

7. GPC Traces - Effect of [VF2] on MWD
75 °C, 4000 psig,  = 20 minutes
Bimodal MWDs observed when [VF2]0 greater than about 1.9 M

8. Suspension Schematic

9. polymer micro-droplets
Suspension Polymerization
Aqueous Continuous phase
• Vertical flow pattern
• Presence of stabilizers
Addition of
monomer
dispersed phase
Monomer beads
Polymer beads
Suspension
polymerization in
polymer micro-droplets
• Controlled agitation
• Coagulation prevented
• Particle diameter range
30mm to 2mm

10. Method of Separation Particles after sieving Broad size distribution
Copolymer particles separated into fractions
with US standard sieves using a sieve shaker
Broad size distribution
250mm sieve
125mm sieve
75mm sieve
100mm
45mm sieve
100mm
* All pictures are optical micrographs

11. Suspension Polymerization
Considerations:
Stabilizers used:
water-soluble polymers: i.e. poly(vinyl alcohol)
Hard to control particle size – separate with sieves
Two phase system only with shear, can’t recover colloidal system
Used for: styrene, (meth)acrylic esters, vinyl chloride, vinyl acetate
Chromatographic separation media, affinity columns, etc

12. Porosity Investigations
Application to transition-metal catalysis and enzymatic catalysis
Highly porous particles (high specific surface area) will permit an improved activity of the system by increasing the density of actives sites per unit of volume
Porosity potential by incorporating various porogens (solvent, non-solvent or linear polymer)
Toluene has been successfully investigated
Porosity evaluation by performing SEM and N2-BET

13. Porosity Investigations
Visual Appearance of Cross-linked fluoropolymer beads
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm
1 mm 1 1 1 1 1 1 m m m m m m m m m 1 1 1 1 1 1 1 1 m m m m m m m m m S S c c a a n n n n i i n n g g e e l l e e c c t t r r o o n n m m i i c c r r o o g g r r a a p p h h s s
Sample Styrene (wt%) EGDMA (wt%) FOMA (wt%) Surface Area* (m2/g)
Non-porous
Porous **
* Surface area measured by N2-BET, error 1%, ** Toluene used as porogen (100% v/v monomer)

14. Potential Utility of CO2
CO2 is non-toxic, cheap and readily available
CO2 is a by-product from production of ammonia, ethanol, hydrogen
CO2 is found in natural reservoirs and used in EOR
Easily of separated and recycled
CO2 has a low surface tension, low viscosity
Liquid and supercritical states “convenient”
Inert for many chemistries 7

15. CO2 is a Variable and Controllable Solvent
Like a gas - but high density
Like a liquid - but low surface tension
Low viscosity, high diffusivity
Nonflammable, environmentally friendly, cost effective, processes at moderate P, T
SCF
Liquid Pc
Pressure
Solid
Gas Tc
Temperature
Gas Gas/Liq SCF

16. Solubility in CO2 1- Phase 2- Phase Scattering Studies
critical point
Dilute globules
Ideal coils
Concentration
Pressure
Scattering Studies
Determined key molecular parameters (<Mw>, Rg, A2)
CO2 found to be a “good” solvent for fluoropolymers
“Synthesis of Fluoropolymers in Supercritical Carbon Dioxide”
DeSimone et. al. Science 1992, 257,
“SANS of Fluoropolymers Dissolved in Supercritical CO2”;
DeSimone et. al. J. Am. Chem. Soc. 1996, 118, 917.

17. Polymer Solubility in CO2
“CO2-philic”
“CO2-phobic”
Oleophilic Hydrophilic
PPO PEO
PVAc PAA
PIB PVOH
PS... PHEA...
1) Fluoropolymers
Siloxanes
Poly(ether carbonates)… Beckman et. al. Nature
f(MW, morphology, topology, composition, T, P)
“Synthesis of Fluoropolymers in Supercritical Carbon Dioxide”
DeSimone et. al. Science 1992, 257,
“Dispersion Polymerizations in Supercritical Carbon Dioxide”
DeSimone et. al. Science 1994, 265,

18. Homogeneous solution polymerizations (up to 65% solids)
“Synthesis of Fluoropolymers in Supercritical Carbon Dioxide”
DeSimone et. al. Science 1992, 257,
Homogeneous solution polymerizations (up to 65% solids)
High molecular weights (ca. 106 g/mol)
Supercritical or liquid CO2
Low viscosities
Wide range of copolymers
- solubility function of fluorocarbon content

19. Dispersion Mechanism Δ M monomer initiation particle nucleation
homogeneous
Particle growth
dispersed polymer particles grow
M monomer
I initiator
stabilizer
polymer

20. Dispersion Polymerization
Considerations:
Relatively large particle size (0.5-5 μm);
Typically narrow Particle Size Distribution
Resulting polymer in colloid (application dependent)
Not common, most examples synthesized from organic solvents, not water
Major application: xerography, ink jets

21. Monomer + Surfactant + Initiator Polymer heat
“Dispersion Polymerizations in Supercritical Carbon Dioxide”
DeSimone et. al. Science 1994, 265,
CO2
Monomer Surfactant + Initiator
Polymer
heat
High conversion
High molecular weights
Stable latexes
Dry powders
Narrow particle size distributions
Spherical particle morphology
Different polymerization kinetics
Composite latex particles possible
Allows for new coating opportunities

22. Structured Particles Containing a Reactive Functional Polymer
Poly(glycidyl methacryate)
(PGMA)
Poly(isocyanatoethyl methacrylate)
(PIEM)
Reactive epoxy functionality
Can react with amines, enzymes…
Can react in an epoxy resin
Reactive isocyanate functionality
Isocyanates react with water, alcohols…
Difficult to synthesize in a aqueous
emulsion or dispersion
Can form crosslinking polyurethane
linkages with an alcohol-containing polymer

23. TEM Images of PIEM/PS
100 nm
Composition:
14 mol% PIEM
86 mol% PS