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Emulsion Polymerization (2)

Emulsion Polymerization (2). External variable (surfactant concentration) used to increase BOTH molecular weight as well as rate of polymerization Colloidal system easy to control Thermal, viscosity issues Reaction mixture in form of final product for coatings

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Emulsion Polymerization (2)

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  1. Emulsion Polymerization (2) • External variable (surfactant concentration) used to increase BOTHmolecular weight as well as rate of polymerization • Colloidal system easy to control • Thermal, viscosity issues • Reaction mixture in form of final product for coatings • Reaction product needs to be isolated from aqueous latex for many applications like rubber, elastomers, PVC, fluoropolymers, etc

  2. Variables and Other Characteristics • Redox Initiators • Hydrogen Peroxide w/ Ferrous Ion • Surfactant-Free Emulsion Polymerization • Initiator fragment affords amphiphilic character • Phase transfer catalysis (cyclodextran) • Microemulsion, Miniemulsion • Inverse emulsions • Core-Shell Particles • pH Control: Hollow Particles

  3. Various Emulsions • Emulsion Polymerization (macro) • Classic aqueous system • Particles range from 50-500 nm • Microemulsion Polymerization • Optically clear, smaller particles • No droplets, just micelles • Miniemulsion Polymerization • Between macro and micro systems, monomer droplets smaller than in macro systems

  4. Inverse Emulsion Polymerization • Standard emulsion polymerization uses water as the continuous phase, or oil-in-water (O/W) • Inverse Emulsions use: • Oil as the continuous phase, or water-in-oil (W/O) • Hydrophilic monomer (or aqueous solution of monomer) dispersed in oil, i.e. xylene/hexane • Like Acrylamide • Oil Soluble Initiator • Surfactant

  5. Surfactants H2O Oil

  6. Water 1% 1% 2% - 2% V V V 3% 3% V+L Multi M a R 4% 4% 5% CTAT 5% SDBS cationic surfactant anionic surfactant 1% 2% 3% 4% V Vesicles Multi Multiphase Region R Rod-like Micelles V + L Vesicles and Lamellar Phase a M Micelles Surfactant Assemblies - Rich Morphologies

  7. M P• PM• M Polymer Particle M M M M M Controlled Radical Polymerization in Microemulsion Monomer-Swollen Micelles Monomer Diffusion Microemulsion Nanoparticles Liu, S. Y.; Kaler, E. W. et al. Macromolecules 2006, 39, 4345

  8. Design of Polymeric Nanogelsfor DNA Delivery • Research Objectives: • Design nanogels < 200 nm in diameter using inverse micro-emulsion techniques with excellent solution stability (w/o toxic solvents!) • Control release profile of DNA by selection of monomer and crosslinker • composition and concentration • 3. Attach targeting ligands to surface of nanogels Release of DNA Diffusion Pathway McAllister, K.; Sazani, P.; Adam, M.; Cho, M.; Rubinstein, M.; Samulski, R. J.; DeSimone*, J. M. J. Am. Chem. Soc. 2002, 15198-15207

  9. Microemulsion Polymerizationand Isolation of Nanogels Addition of Initiator to oil phase and free radical polymerization Removal of heptane and surfactant by extraction and dialysis Step 1: Form microemulsion Step 2: Polymerize microemulsion Step 3: Extract and purify nanogels

  10. Designing Polymeric Nanogels Increasing Crosslinker + + + + + + Increasing Charge + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Monomers Nanogels PEGdiacrylate n=8 2-Hydroxyethylacrylate 2-Acryloxytrimethyl- ammonium chloride

  11. Dynamic Light Scattering of Microemulsion Before and After Polymerization = 0% Cationic Monomer = 12% Cationic Monomer = 25% Cationic Monomer Diameter (nm) Crosslinker Concentration (wt %) After Polymerization Before Polymerization After Before

  12. Cross-linked Particles Adsorbed to Surface Low Crosslinking Particles Flatten and Spread High Crosslinking Particles Maintain Shape

  13. TEM Images of Nanogels 3% Crosslinker 50% Crosslinker 12% Crosslinker 0% Charge 12% Charge 66K Magnification Samples Stained with 1% PTA

  14. % HeLa Cells Living After 40 Hour Exposure to Nanogels % HeLa Cells Living Cationic (12%) Cationic (25%) Blank Non-ionic Polylysine

  15. Release of Dye Molecules from Non-ionic Nanogels Final Fluorescence Intensity in Bag Initial Fluorescence Intensity in Bag Dialysis for 24 hours at 37°C and at 4°C 37°C = 100% 4° C = 100% 37°C = 4% 4° C = 8%

  16. In Vitro Efficacy:Nanogel Uptake by HeLa Cells HeLa Cells Cells + Nanogels Nanogels Bound to Cells Add Nanogels Wash Cells

  17. HeLa Cells Exposed to Nanogels 0% Charge 12% Charge 25% Charge HeLa Cells Viewed at 400 x Magnification After 24 h exposure to nanogels (12% cross-linker) and PBS wash

  18. Confocal Microscopy of HeLa Cells Exposed to Rhodamine-Labeled Nanogels 0% Charge 12% Charge 25% Charge 3% Crosslinker 12% Crosslinker

  19. Future Directions • Determine maximum DNA length which does not induce aggregation • Evaluate in vitro delivery of DNA with nanogel/DNA complexes • Extend to hydrolytically degradable matrices, targeting ligands, diffusion barriers • Extend to peptides, pharmaceuticals, vaccines

  20. Murthy N et al. PNAS 2003;100:4995-5000

  21. Miniemulsion Polymerization for Dually-Triggered Degradable Nanogels Li, Z. C, et al. et al. J. Controlled Release 2011, 152, 57

  22. Core-shell Polymer Particles • General Practical Uses: • impact modification (soft core, hard shell) • providing chemical reactivity to latex particles • enhancement of adhesion properties (hard core, soft shell) • controlled-release drug delivery (water-soluble core) • prevent colors from showing through (hollow core) shell core Morphology: is determined by thermodynamic control (lowest surface free energy) and kinetic control. The second polymer doesn’t necessarily form the shell!

  23. Possible Morphologies 1st-stage polymer 2nd-stage polymer Thermodynamically Stable Morphologies Core-shell Inverted core-shell Half-Moon A Half-moon B Kinetically Trapped Morphologies Microdomains Raspberry Sandwich A B A B

  24. Hollow Particles & Ropaque™ Lower pH Raise pH microvoid Hollow particles in: paints, sunscreens, inks, cosmetics, fluorescent coatings, forgery- or counterfeiting-proof coated paper, paper products, etc. • Hollow polymer particles industrially important • Can replace use of TiO2 • Ropaque™ made by Rohm & Haas Kowalski, A.; Vogel, M. U.S. Patent 4,469,825. Blankenship, R.M.; Finch, W.C.; Mlynar, L.; Schultz, B.J. U.S. Patent 6,139,961.

  25. Hollow Particle Micrographs PMMA particles via W/O/W emulsion polymerization Core-shell hollow particles using methacrylic acid J. Poly. Sci. A: Polym. Chem., 2001, 39, 1435 Colloid Polym. Sci. 1999, 277, 252.

  26. Emulsion Polymerization for Dye-Labeled Nanoparticles Zhu, M. Q.; Li, A. D. Q. et al. J. Am. Chem. Soc. 2006, 128, 4303

  27. PGMA macroCTA as a Steric Stabiliser for the Aqueous Dispersion Polymerisation of HPMA Y. T. Li and S. P. Armes, Angewandte Chem., 2010, 49, 4042 PGMA65 RAFT CTA HPMA Targeting a longer core-forming block relative to the stabiliser block should lead to progressively larger sterically-stabilised nanolatexes?

  28. Scanning Electron Microscopy Studies Y. T. Li and S. P. Armes, Angewandte Chem., 2010, 49, 4042 105 nm PGMA65-PHPMA300latex 90 nm PGMA65-PHPMA200latex SEM images confirm spherical, near-monodisperse latexes

  29. Transmission Electron Microscopy Studies Y. T. Li and S. P. Armes, Angewandte Chem., 2010, 49, 4042 PGMA65-PHPMA50 PGMA65-PHPMA70 PGMA65-PHPMA100 200 nm 200 nm 200 nm Dh = 40 nm Dh = 29 nm Dh = 58 nm Negative staining using uranyl formate: Prof. S. Sugihara and Dr. A. Blanazs Scale bar: 100 nm

  30. DMF GPC Studies of PGMA-PHPMA Block Copolymers A. Blanazs, S. P. Armes, A. J. Ryan et al., J. Am. Chem. Soc. 2011, ASAP Aldrich-sourced HPMA has only 0.10 mol % dimethacrylate impurity Best result: Mw/Mn < 1.20 for G47-H1000 at 99 % conv. (within 2 h at 70oC) ! So excellent control over MWD and good CTA blocking efficiencies….

  31. More In Situ Studies: PGMA47-PHPMAx 77.5 min = 68 %, DP 131 84 mins = 75 %, DP 150 87 mins = 78 % DP 156 75 min = 62 %, DP 123 90 mins = 82 %, DP 164 225 mins = 100 % DP 200 65 min = 46 %, DP 92 • Blanazs, S. P. Armes, • J. Madsen, A. J. Ryan • and G. Battaglia • JACS, 2011, ASAP Scale bars: 200 nm

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