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Defense

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Presentation for my thesis defense.

Presentation for my thesis defense.

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  • The reason polymer-particle systems are of interest is that they can be used to study a number of systems. For example… Don’t talk too long about this!
  • The reason polymer-particle systems are of interest is that they can be used to study a number of systems. For example… Don’t talk too long about this!
  • I: Au(2) PS(10)-SH; P = 125, N = 10; sigma = 1.67 II: Au(5) PS(10)-SH; P = 125, N = 10; sigma = 1.39 III: Au(2) PS(10)-SH; P = 125, N = 480; sigma = 9.21 Tell why we model plate + brush
  • Say it right!
  • poly~methyl methacrylate! ~PMMA! and poly~vinyl chloride! ~PVC!, poly~styrene! ~PS!, and poly~2,6-dimethyl-1,4-phenylene oxide! ~PXE! State objectives differently – motivate how we are extending the problem from the limiting cases
  • Mention the presence of two kinds of chains We are proposing that SCFT provides a good way to study these systems
  • I: Au(2) PS(10)-SH; P = 125, N = 10; sigma = 1.67 II: Au(5) PS(10)-SH; P = 125, N = 10; sigma = 1.39 III: Au(2) PS(10)-SH; P = 125, N = 480; sigma = 9.21 Tell why we model plate + brush
  • What really matters is fEff
  • Describe the interplay between enthalpy and entropy using SST Term 4 distinguishes the theory from autophobic Term 4 should be smaller for larger f Random copolymer should rearrange itself toward f = 1 Idea: modify term 4 based on fEff
  • I: Au(2) PS(10)-SH; P = 125, N = 10; sigma = 1.67 II: Au(5) PS(10)-SH; P = 125, N = 10; sigma = 1.39 III: Au(2) PS(10)-SH; P = 125, N = 480; sigma = 9.21 Tell why we model plate + brush
  • I: Au(2) PS(10)-SH; P = 125, N = 10; sigma = 1.67 II: Au(5) PS(10)-SH; P = 125, N = 10; sigma = 1.39 III: Au(2) PS(10)-SH; P = 125, N = 480; sigma = 9.21 Tell why we model plate + brush
  • I: Au(2) PS(10)-SH; P = 125, N = 10; sigma = 1.67 II: Au(5) PS(10)-SH; P = 125, N = 10; sigma = 1.39 III: Au(2) PS(10)-SH; P = 125, N = 480; sigma = 9.21 Tell why we model plate + brush
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Curvature?
  • Transcript

    • 1. Modification of Surfaces Using Polymers: A Self-consistent Field Theory Study David Trombly Advised by Venkat Ganesan Thesis Defense June 29, 2011
    • 2. Polymer-grafted surface Interacting surface Mediating material Solvent Melt
        • Biocompatible surfaces
        • Preventing immune-response induced thrombosis
      R drug H brush R protein σ Surface-surface interactions
        • Water purification
        • Targeted drug delivery
    • 3. Polymer-grafted surface Interacting surface Mediating material Solvent Melt http://www.questline.com/images/content/CMPND_nanocomposites.jpg Surface-surface interactions
        • Polymer thin films/electronic materials
      Surface-polymer interactions
    • 4. Polymer-grafted surface Interacting material Homopolymer Surface-polymer interactions Diblock copolymer Random copolymer brush Stoykovich, et al., Science, 2005 B A
    • 5. Polymer-grafted particle Interacting surface Mediating material Solvent Melt
        • Biocompatible surfaces
        • Custom particles
        • Preventing immune-response induced thrombosis*
      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. Drug design equation
        • Trombly and Ganesan, JPS(B), 2009
    • 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
        • Meli, et al, Soft Matter, 2009
      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. Width/energy collapse, correlation
        • Trombly and Ganesan, JCP, 2010
    • 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
        • Mansky et al, Science, 1997
      • Model a homopolymer thin film on top of a random copolymer brush
      • Study the effect of f, segment-segment interaction, chain lengths, grafting density on surface energy
      Objectives (Ch 4)
    • 10. Wetting Dewetting σ = 2.45, α = 0.5 σ = 4.90, α = 1.5
        • Ferriera, et al, Macro, 1998
      Happens sooner for larger σ (more stretched chains)! Surface energy
        • Matsen and Gardiner, JCP, 2001
      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.
        • Kim, et al, Macro, 2009
      Background: f = 0
        • Borukhov and Leibler, 2000
      Objectives
      • Model a homopolymer thin film on top of a random copolymer brush
      • Surface energies as a function of f, χ N, α , σ , λ
    • 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.
      • Mimic experiment by using conditional probabilities to create sequences of random chains (f, λ )
      Modeling random copolymers
      • How do we model the random chains?
      • Solve the equations, average the results
      • n = 500, average the results of two independent runs
        • Fredrickson, et al, Macromolecules, 1992
      λ = -0.5 λ = 0.5 λ = 0
    • 14.
      • Used to build a modified strong-stretching theory
      Chain rearrangement
        • Trombly, Pryamitsyn and Ganesan, JCP, 2011
      f Eff f Eff f = 0. 5 f = 0. 5
    • 15. Strong-stretching theory (SST)
        • Kim, et al, Macromolecules, 2009
      Configurational entropy cost due to the interface Translational entropy Enthalpic interactions
        • Matsen and Gardiner, JCP, 2001
        • Semenov, Macro, 1993
      Stretching energy χ Eff = χ (1-f Eff )
    • 16. Surface energy results Autophobic ~ 5 x 10 -3
        • Trombly, Pryamitsyn and Ganesan, JCP, 2011
      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
      • Autophobic trends
    • 17. Blockiness and chain rearrangement
        • Trombly, Pryamitsyn and Ganesan, Submitted to JCP, 2011
      • Rearrangement of the grafted chains
      f = 0.5 f = 0.5
    • 18. Blockiness and chain rearrangement
        • Trombly, Pryamitsyn and Ganesan, Submitted to JCP, 2011
      • Rearrangement of the grafted chains
      f = 0.5 f = 0.5
    • 19. Summary
      • SCFT and SST used to describe random copolymer brush + homopolymer melt
      • Chain rearrangement
      • Surface energies as a function of f, χ N, α , σ , λ
      Extension (Ch 5)
      • Model a diblock coploymer thin film on a random copolymer brush
    • 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.
      • Interpenetration of brush and diblock
      • Rearrangement effects
      Parallel morphologies
    • 22.
      • Splaying effects – enables the creation of a more neutral surface
      • Rearrangement effects (more pronounced the parallel)
      Perpendicular morphologies
    • 23.
      • Minimal splaying effects
      • Very enhanced rearrangement
      Blocky random copolymer
    • 24.
      • Enhanced splaying of A diblock
      • Assymetric splaying and rearrangement of brush
      Increased A in brush (f = 0.6)
    • 25.
      • Bulk spacing preserved
      • “ Super neutrality” due to splaying and rearrangement effects
      Energy picture D bulk
      • Transition to parallel morphologies with increasing f
    • 26. Neutral windows
      • More blocky: larger neutral window due to increased difference in rearrangement between perpendicular and parallel
      • “ Super neutrality” due to splaying and rearrangement effects
    • 27. Neutral windows
      • Neutral windows uncorrelated with surface energies
      • No “neutral window” of surface energies can be drawn.
    • 28. Summary
      • SCFT and SST used to describe random copolymer brush + diblock copolymer melt
      • Pictures of morphology, chain rearrangement
      • Neutral as a function of f, α , σ , λ
    • 29. Future work
      • Modeling grafted water-soluable polymers
      • Modeling the effects of air and substrate surface interactions on the phase behavior of diblock copolymer thin films
      • Exploring the phase behavior of random-block copolymers
      • Exploring the phase behavior of thin films of assymetric diblock copolymers on random copolymer brushes
    • 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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