Defense

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Presentation for my thesis defense.

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Defense

  1. 1. Modification of Surfaces Using Polymers: A Self-consistent Field Theory Study David Trombly Advised by Venkat Ganesan Thesis Defense June 29, 2011
  2. 2. Polymer-grafted surface Interacting surface Mediating material Solvent Melt <ul><ul><li>Biocompatible surfaces </li></ul></ul><ul><ul><li>Preventing immune-response induced thrombosis </li></ul></ul>R drug H brush R protein σ Surface-surface interactions <ul><ul><li>Water purification </li></ul></ul><ul><ul><li>Targeted drug delivery </li></ul></ul>
  3. 3. Polymer-grafted surface Interacting surface Mediating material Solvent Melt http://www.questline.com/images/content/CMPND_nanocomposites.jpg Surface-surface interactions <ul><ul><li>Polymer thin films/electronic materials </li></ul></ul>Surface-polymer interactions
  4. 4. Polymer-grafted surface Interacting material Homopolymer Surface-polymer interactions Diblock copolymer Random copolymer brush Stoykovich, et al., Science, 2005 B A
  5. 5. Polymer-grafted particle Interacting surface Mediating material Solvent Melt <ul><ul><li>Biocompatible surfaces </li></ul></ul><ul><ul><li>Custom particles </li></ul></ul><ul><ul><li>Preventing immune-response induced thrombosis* </li></ul></ul>R drug H brush R protein σ R g 2 Interaction energy determined by: σ www.mdconsult.com Polymer-grafted sphere – bare sphere (Ch 2) R protein R drug H brush R drug
  6. 6. Drug design equation <ul><ul><li>Trombly and Ganesan, JPS(B), 2009 </li></ul></ul>
  7. 7. Polymer-grafted particle Interacting surface Mediating material Solvent Melt The following contribute to miscibility: Decrease: Increase: N brush N free translational entropy σ R g 2 <ul><ul><li>Meli, et al, Soft Matter, 2009 </li></ul></ul>Polymer-grafted spheres in a melt (Ch 3) R core H brush R particle N free N brush H brush R core R particle R g, free
  8. 8. Width/energy collapse, correlation <ul><ul><li>Trombly and Ganesan, JCP, 2010 </li></ul></ul>
  9. 9. Semiconductor devices (Ch 4-5) Equal surface energies Perpendicular lamellae High value semiconductor devices Random copolymer brush f A B f = volume fraction of A (in brush) B A <ul><ul><li>Mansky et al, Science, 1997 </li></ul></ul><ul><li>Model a homopolymer thin film on top of a random copolymer brush </li></ul><ul><li>Study the effect of f, segment-segment interaction, chain lengths, grafting density on surface energy </li></ul>Objectives (Ch 4)
  10. 10. Wetting Dewetting σ = 2.45, α = 0.5 σ = 4.90, α = 1.5 <ul><ul><li>Ferriera, et al, Macro, 1998 </li></ul></ul>Happens sooner for larger σ (more stretched chains)! Surface energy <ul><ul><li>Matsen and Gardiner, JCP, 2001 </li></ul></ul>Background: f = 1 (autophobic) Increased free chain length ( α ) α = Same effect from decrease of brush chain length (increases α ) Ends of free chains are stretched at interface; reduction of interfacial area is preferred N free N brush
  11. 11. <ul><ul><li>Kim, et al, Macro, 2009 </li></ul></ul>Background: f = 0 <ul><ul><li>Borukhov and Leibler, 2000 </li></ul></ul>Objectives <ul><li>Model a homopolymer thin film on top of a random copolymer brush </li></ul><ul><li>Surface energies as a function of f, χ N, α , σ , λ </li></ul>
  12. 12. Self-consistent field theory (SCFT) w A ( r ), w B ( r ) q( r ,s) q c ( r ,s) s Stretching energy Enthalpy Incompressibility Grafted Free
  13. 13. <ul><li>Mimic experiment by using conditional probabilities to create sequences of random chains (f, λ ) </li></ul>Modeling random copolymers <ul><li>How do we model the random chains? </li></ul><ul><li>Solve the equations, average the results </li></ul><ul><li>n = 500, average the results of two independent runs </li></ul><ul><ul><li>Fredrickson, et al, Macromolecules, 1992 </li></ul></ul>λ = -0.5 λ = 0.5 λ = 0
  14. 14. <ul><li>Used to build a modified strong-stretching theory </li></ul>Chain rearrangement <ul><ul><li>Trombly, Pryamitsyn and Ganesan, JCP, 2011 </li></ul></ul>f Eff f Eff f = 0. 5 f = 0. 5
  15. 15. Strong-stretching theory (SST) <ul><ul><li>Kim, et al, Macromolecules, 2009 </li></ul></ul>Configurational entropy cost due to the interface Translational entropy Enthalpic interactions <ul><ul><li>Matsen and Gardiner, JCP, 2001 </li></ul></ul><ul><ul><li>Semenov, Macro, 1993 </li></ul></ul>Stretching energy χ Eff = χ (1-f Eff )
  16. 16. Surface energy results Autophobic ~ 5 x 10 -3 <ul><ul><li>Trombly, Pryamitsyn and Ganesan, JCP, 2011 </li></ul></ul>χ N = 10, α = 1, σ = 4.9, λ = 0 f = 0.5, α = 1, σ = 4.9, λ = 0 f = 0.5, χ N = 10, σ = 4.9, λ = 0 f = 0.5, χ N = 10, α = 1, λ = 0 <ul><li>Autophobic trends </li></ul>
  17. 17. Blockiness and chain rearrangement <ul><ul><li>Trombly, Pryamitsyn and Ganesan, Submitted to JCP, 2011 </li></ul></ul><ul><li>Rearrangement of the grafted chains </li></ul>f = 0.5 f = 0.5
  18. 18. Blockiness and chain rearrangement <ul><ul><li>Trombly, Pryamitsyn and Ganesan, Submitted to JCP, 2011 </li></ul></ul><ul><li>Rearrangement of the grafted chains </li></ul>f = 0.5 f = 0.5
  19. 19. Summary <ul><li>SCFT and SST used to describe random copolymer brush + homopolymer melt </li></ul><ul><li>Chain rearrangement </li></ul><ul><li>Surface energies as a function of f, χ N, α , σ , λ </li></ul>Extension (Ch 5) <ul><li>Model a diblock coploymer thin film on a random copolymer brush </li></ul>
  20. 20. Previous modeling work Matsen, JCP, 1997 B A Diblock on hard surface with preference for A Incommensurate Diblock on hard surface with chemical stripes Wang, et al, Macro, 2000 Commensurate D bulk B A
  21. 21. <ul><li>Interpenetration of brush and diblock </li></ul><ul><li>Rearrangement effects </li></ul>Parallel morphologies
  22. 22. <ul><li>Splaying effects – enables the creation of a more neutral surface </li></ul><ul><li>Rearrangement effects (more pronounced the parallel) </li></ul>Perpendicular morphologies
  23. 23. <ul><li>Minimal splaying effects </li></ul><ul><li>Very enhanced rearrangement </li></ul>Blocky random copolymer
  24. 24. <ul><li>Enhanced splaying of A diblock </li></ul><ul><li>Assymetric splaying and rearrangement of brush </li></ul>Increased A in brush (f = 0.6)
  25. 25. <ul><li>Bulk spacing preserved </li></ul><ul><li>“ Super neutrality” due to splaying and rearrangement effects </li></ul>Energy picture D bulk <ul><li>Transition to parallel morphologies with increasing f </li></ul>
  26. 26. Neutral windows <ul><li>More blocky: larger neutral window due to increased difference in rearrangement between perpendicular and parallel </li></ul><ul><li>“ Super neutrality” due to splaying and rearrangement effects </li></ul>
  27. 27. Neutral windows <ul><li>Neutral windows uncorrelated with surface energies </li></ul><ul><li>No “neutral window” of surface energies can be drawn. </li></ul>
  28. 28. Summary <ul><li>SCFT and SST used to describe random copolymer brush + diblock copolymer melt </li></ul><ul><li>Pictures of morphology, chain rearrangement </li></ul><ul><li>Neutral as a function of f, α , σ , λ </li></ul>
  29. 29. Future work <ul><li>Modeling grafted water-soluable polymers </li></ul><ul><li>Modeling the effects of air and substrate surface interactions on the phase behavior of diblock copolymer thin films </li></ul><ul><li>Exploring the phase behavior of random-block copolymers </li></ul><ul><li>Exploring the phase behavior of thin films of assymetric diblock copolymers on random copolymer brushes </li></ul>
  30. 30. Acknowledgements Prof. Venkat Ganesan, Committee members, Ganesan research group (Victor Pryamitsyn, Manas Shah, Landry Khounlavong, Paresh Chokshi, Ben Hanson, Arun Narayana, Chetan Mahajan, Thomas Lewis, Gunja Pandav), Brandon Rawlings Funding: NSF (Award # 1005739) Robert A. Welch Foundation Grant F1599 US Army Research Office Grant W911NF-10-1-0346 Texas Advanced Computing Center

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