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Polypyrrole /polyurethane ( PyPU ): a conducting polymer- elastomer composite

Polypyrrole /polyurethane ( PyPU ): a conducting polymer- elastomer composite . Craig Milroy (group presentation #5) 5/24/2011. Electrospun Nanofibers. Ideal for applications that require large surface area-to-volume battery separators membranes tissue engineering scaffolds catalysts

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Polypyrrole /polyurethane ( PyPU ): a conducting polymer- elastomer composite

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  1. Polypyrrole/polyurethane (PyPU): a conducting polymer-elastomer composite Craig Milroy (group presentation #5) 5/24/2011

  2. ElectrospunNanofibers Ideal for applications that require large surface area-to-volume • battery separators • membranes • tissue engineering scaffolds • catalysts ***Controlled porosity*** Li, Xia. Adv Mat 2004; 16(14): 1151-1170.

  3. Research Objective: • identify appropriate solvent for electrospinningPyPU Methods: • synthesizePyPU (1:5 wt/wt; emulsion polymerization) • prepare 8-20 wt% solutions: • CHCl3 • DMF/THF (100/0, 70/30, 50/50, 30/70, 0/100)* • HFIP *Khil, Cha, Kim, Bhattarai. ElectrospunNanofibrous Polyurethane Membrane as Wound Dressing. JBMR 2003, 67B:675-679.

  4. Electrospinning Apparatus Taylor Cone Stable Jet Bending Instability Adapted from: Bhardwaj, 2010 SEM image from Xia, 2004

  5. videos http://www.scivee.tv/node/26466

  6. Results (THF):

  7. Results (HFIP):

  8. Rayleigh Instability (revisited) • Governing Equations: • Conservation of Mass (Continuity) • Conservation of Momentum (Navier-Stokes) • Consider a sinusoidal perturbation to an axisymmetric cylindrical jet: • k : wavenumber ( ) • ω : growth rate of perturbation • ω > 0 instability grows • ω < 0 instability decays • ω = 0 standing wave • Dispersion Relationship a η ω Hohman 01

  9. Linear Stability Analysis of Jet Dispersion relations when > 0 • Dispersion Relation: • Apply similar perturbations • Equation is cubic, thus three branches • Two destabilizing branches: • Rayleigh mode – is suppressed as electric field is increased • Conducting mode – is enhanced as electric field is increased. • Destabilizing if Re ω > 0 Hohman 01

  10. Summary • Both THF and HFIP appear to be promising solvents • Next steps: • More thorough characterization of starting solution: (viscosity, surface tension) • More thorough investigation of electrospinning parameters: (applied voltage, working distance, field strength) • Modify electrospinning configuration (vertical) • Investigate parameter ranges for which Raleigh instability is suppressed (as a function of parameter values)

  11. QUESTIONS?

  12. References • Bhardwaj N, Kundu S. Electrospinning: A fascinating fiber fabrication technique. Biotechnology Advances 2010; 28:325-347. • Hohman MM, Shin M, Rutledge G, Brenner MP. Electrospinning and electrically forced jets. I. Stability Theory. Physics of Fluids 2001; 13:2201-2220. • Reneker DH, Yarin AL, Fong H, Koombhongse S. Bending instability of electrically charged liquid jets of polymer solutions in electrospinning. Journal of Applied Physics 2000; 87:4531-4547. • Xia, 2004.

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