1. Modification of Surfaces Using Polymers: A Self-consistent Field Theory Study David Trombly Advised byVenkat Ganesan Thesis Defense June 29, 2011

2. Polymer-grafted surface Interacting surface Mediatingmaterial Solvent Melt

• Biocompatible surfaces

• Preventing immune-response induced thrombosis

R drug H brush R protein Surface-surface interactions

• Water purification

• Targeted drug delivery

3. Polymer-grafted surface Interacting surface Mediatingmaterial 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 Mediatingmaterial Solvent Melt

• Biocompatible surfaces

• Custom particles

• Preventing immune-response induced thrombosis*

R drug H brush R protein R g 2 Interaction energy determined by: 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 Mediatingmaterial Solvent Melt The following contribute to miscibility: Decrease: Increase: N brush N free translational entropy 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 energiesPerpendicular lamellaeHigh 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 = 2.45,= 0.5 = 4.90,= 1.5

• Ferriera, et al, Macro, 1998

Happens sooner for larger(more stretched chains)! Surface energy

• Matsen and Gardiner, JCP, 2001

Background: f = 1 (autophobic) Increased free chain length ( ) = Same effect from decrease of brush chain length (increases ) 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, N, , ,

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, )

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

= -0.5 = 0.5 = 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 Eff= (1-f Eff ) 16. Surface energy results Autophobic ~ 5 x 10 -3

• Trombly, Pryamitsyn and Ganesan, JCP, 2011

N = 10,= 1,= 4.9,= 0 f = 0.5,= 1,= 4.9,= 0 f = 0.5, N = 10,= 4.9,= 0 f = 0.5, N = 10,= 1,= 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, N, , ,

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, , ,

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. AcknowledgementsProf. 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