INTEGRATION OF NATURAL POLYMERS AND SYNTHETIC NANOSTRUCTURES. Vladimir V. Tsukruk

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1 INTEGRATION OF NATURAL POLYMERS AND SYNTHETIC NANOSTRUCTURES Vladimir V. Tsukruk School of Materials Science and Engineering Georgia Institute of Technology AFOSR Program Review 2011 AFOSR, FA Grant ( ) Hugh De Long Review, January

2 elastic modulus/max strain INTEGRATION OF NATURAL POLYMERS AND NANOSTRUCTURES Vladimir V. Tsukruk, Georgia Institute of Technology Focus: novel strategies for combining natural polymers and synthetic nanostructures Status quo: empirical approaches for hybrid nanocomposites with natural polymer component; little understanding of multi-length phenomena at interfaces between natural polymer and synthetic organic-inorganic nanostructures New Insight: understanding directed assembly of natural oligomers and polymers at interfaces and principles of molecular reinforcement; silk fibroin and silk-based materials integration with novel assembling and processing routines AFOSR Program Review 2011 Main achievements to date: discovery of potential mechanism of weaker in silkfiller interfaces due to trapped nanobubbles; exploration of secondary structure transitions for nanopatterning of silk films; design of ultra-strong silkgraphene nanocomposites with molecular interphases E GPa % silk, 50 nm PLA silk, MeOH silk, X-linked silk-aunpsilk-sinpsilk-agnpssilk-clay silk-clay-x-linksilk-go ultrathin silk interfaces (30-80 nm) Quantitative impact: reinforced silk interphasial nanocomposites with layered graphene oxide: elastic modulus reaches 150 Gpa and ultimate strength is about 330 MPa Research goals and longterm impact: The ultimate goal: strategies for combining natural polymers and synthetic nanostructures to achieve extreme properties Prospective tough and flexible bio-derived/enabled nanocomposites; strong and elastomeric nanostructured biologicalsynthetic interfaces with record strength 2

3 GOAL AND OBJECTIVES AFOSR Program Review 2012 The ultimate goal: discovering new strategies for combining natural polymers and synthetic nanostructures Objectives: understanding fundamental mechanisms of molecular reinforcement with focus on self-assembly of silk fibroin under confined conditions. The actual role of silk secondary structure and the possible interface-mediated alteration of silk conformations via intermolecular and intramolecular interactions Investigating the mechanism of the formation of silk-inorganic interfaces by rational integration of silk matrices with inorganic nanostructures by introducing specific interfacial additives. The effect of nanofiller shape, surface chemistry, topology, and dimensions will be studied by utilizing silica nanoparticles, graphene, and metal nanoparticles as nanostructured components. Developing efficient approaches to promote controlled integration of silk and inorganic matrixes by utilizing traditional gelation, one-pot and multilayered LbL methods, filtration, and in-situ nanoparticle growth. Understanding the relationships between the structural, compositional and physical properties of silk-based nanocomposites. Physical properties to be investigated include optical, mechanical, and swelling/diffusion ability, all of which are relevant to sensing applications and originate from the intricate organization, high surface to volume ratio, and unique combination of biological molecules with inorganic nanostructures. 3

4 Progress, 2012 Completed In progress Processing, Microstructure and Morphology Utilization of a-b transformations in silk secondary structures for nanoscale micro-patterning Inner organization of dry/swollen layered silk nanomaterials with neutron reflectivity Morphology and microstructure of freelystanding silk and exfoliated graphene oxide flakes One-pot fabrication of graphene oxide silk gels and nanocomposite graphene paper with ultimate strength and flexibility Adsorption and interactions of silk fibroin with graphene oxide flakes under different processing conditions Silk-nests periodic microarrays via inkjet layerby-layer printing AFOSR Program Review 2012 Fundamental properties of nanocomposites with natural polymers Unique trapped nanobubble morphology of silk-water interfaces Molecular layering of silk backbones and graphene oxide results in new enhancing mechanism via molecular interphases Intimate interactions of heterogeneous silk fibroins backbones and heterogeneous surface regions of flexible graphene flakes as a mechanism for ultrastrong molecular interphase nanocomposites 4

5 Transformative approach Heading toward deeper understanding on major factors affecting molecular events, intermolecular interactions, and transformations at interfaces between inorganic nanostructures and synthetic biological matrices is evolutionary in nature: caseby-case, structure-by-structure, or event-by-event. However, such an accumulation might result into the transformative progress in design of novel biomimetic nanomaterials and structures such as super-tough/strong nanocomposites, robust standalone nanostructures, bioactive coatings, and complex chemical/biological sensing arrays resembling biological materials and receptors. 5

6 Materials, structures, and approaches Assembly/phenomena Imprinted topography Thin shell microcapsules b-b 2 and a-b transitions Ionic-ionic interactions Silk I silk II transition Free and forced adsorption Ink-jet printing Natural polymers Interfaces/nanostructures AFOSR Program Review 2012 Recombinant spider silk Silk fibroin proteins Silk constructs Silk polyelectrolytes Assembly/morph ology/properties Silicon wafers Graphenes Graphene oxides Silica microparticles POSS nanoparticles Metallic nanostructures Flexible substrates 6

7 Materials, structures, and approaches Assembly/phenomena Imprinted topography Thin shell microcapsules b-b 2 and a-b transitions Ionic-ionic interactions Silk I silk II transition Free and forced adsorption Ink-jet printing Natural polymers Interfaces/nanostructures AFOSR Program Review 2012 Recombinant spider silk Silk fibroin proteins Silk constructs Silk polyelectrolytes Assembly/morph ology/properties Silicon wafers Graphenes Graphene oxides Silica microparticles POSS nanoparticles Metallic nanostructures Flexible substrates 7

8 SOME PIECES FROM PREVIOUS YEAR REVISITED Plasma polymerized aminoacid surfaces Neutron reflectivity of swollen silk surface layers - air nanobubles trapped! AFOSR Program Review

Peptide-based composite coatings via plasma polymerization A) PP-Tyr/ACN, B) PP-Tyr/HEMA and C) PP-Tyr/TTIP Tyr ACN HEMA TTIP K. D. Anderson, S. L. Young, H. Jiang, R.

9 Peptide-based composite coatings via plasma polymerization A) PP-Tyr/ACN, B) PP-Tyr/HEMA and C) PP-Tyr/TTIP Tyr ACN HEMA TTIP K. D. Anderson, S. L. Young, H. Jiang, R. Jakubiak, T. J. Bunning, R. R. Naik, V. V. Tsukruk, Plasma Enhanced Co- Polymerization of Amino Acid and Synthetic Monomers, Langmuir, 2012, 28, With Naik, Bunning NDSEG Program

Silk interfacial layers with neutron reflectivity: dry versus swollen state revisiting and revising RQ 4 b/v (nm -2 ) 1E-6 1E-7 (Silk) 7 1E-8 1E-9

2 Q (nm -1 ) 3 beam-line visit to SNS in the past 2 years to solve the puzzle Liquid Reflectometer, BL-4B Spallation Neutron Source Oak Ridge National

Mori silk fibroin protein: spin-assisted LbL films Internal structure and interfacial behavior: Varying number of layers Dry versus swollen state 3.

10 Silk interfacial layers with neutron reflectivity: dry versus swollen state revisiting and revising RQ 4 b/v (nm -2 ) 1E-6 1E-7 (Silk) 7 1E-8 1E-9 (Silk) 1 Silk LbL assembly process 1E Q (nm -1 ) 3 beam-line visit to SNS in the past 2 years to solve the puzzle Liquid Reflectometer, BL-4B Spallation Neutron Source Oak Ridge National Lab Oak Ridge, J. Ankner With Kaplan B. Mori silk fibroin protein: spin-assisted LbL films Internal structure and interfacial behavior: Varying number of layers Dry versus swollen state 3.5x x x x x x x10-5 NR (silk) 1 thickness: 4.5 nm NR (silk) 7 thickness: 26.3 nm B. Wallet, E. Kharlampieva, K. Campbell, V. Kozlovskaya, S. Malak, J. F. Ankner, D. L. Kaplan, V. V. Tsukruk, Silk Layering as Studied with Neutron Reflectivity, Langmuir, 2012, 28, (Silk) (Silk) z (nm)

b/v (nm -2 ) Swelling of silk surface layer results in nanoporous layer with hydrophobic-trapped air nanobubbles!!! b/v (nm -2 ) 8.0x10-4 7.0x10-4 FWHM 1.16 nm 1.05nm D 2 O Interface 6.0x10-4 5.

11 b/v (nm -2 ) Swelling of silk surface layer results in nanoporous layer with hydrophobic-trapped air nanobubbles!!! b/v (nm -2 ) 8.0x x10-4 FWHM 1.16 nm 1.05nm D 2 O Interface 6.0x x *10-4 nm *10-4 nm x x x *10-4 nm z (nm) Silicon Interface Reduced density 1.0x Air Interface 6.0x10-4 (Silk) 1 5.0x x x z (nm) Craig, V. S. J. Very Small Bubbles at Surfaces-the Nanobubble Puzzle, Soft Matter, 2011, 7, x x z (nm)

Swollen silk surface layer with bubbles Dry silk Δt Trapped air bubbles t o t o silicon silicon Segregated silk Reduced scattering length density of silk surface layer (first 5 nm) INSTEAD of

12 Swollen silk surface layer with bubbles Dry silk Δt Trapped air bubbles t o t o silicon silicon Segregated silk Reduced scattering length density of silk surface layer (first 5 nm) INSTEAD of significant increase as expected for uniform swelling process after adding D 2 0 => swollen silk surface layer (swelling rate of 60%) with air nanobubbles (trapped by hydrophobic regions) during wetting and swelling processes And what? => weaker interface in composites!!! B. Wallet, E. Kharlampieva, K. Campbell-Proszowska, V. Kozlovskaya, S. Malak, J. F. Ankner, D. L. Kaplan, V. V. Tsukruk, Silk Layering as Studied with Neutron Reflectivity, Langmuir, 2012, 28,

MAJOR ACHIEVEMENTS Gentle silk micropatterning (a->b, b->b 2 transformations of secondary structures): high resolution without large stresses/contrast for topography and properties

13 MAJOR ACHIEVEMENTS Gentle silk micropatterning (a->b, b->b 2 transformations of secondary structures): high resolution without large stresses/contrast for topography and properties (GSSAAAAAAAASGPGGYGPENQGPSGPGGYGPGGP) 16 AFOSR Program Review 2012 Ultra-strong organized silk fibroingraphene nanocomposites with elastic modulus around 150 Gpa and ultimate strength of 330 MPa 13

Z (nm) Micropatterning Techniques: old new Capillary Transfer Lithography Evaporating toluene Dry PDMS mold 2 w/v% PS PDMS swollen with toluene SAMIM: solvent assisted microcontact molding Dry PDMS

14 Z (nm) Micropatterning Techniques: old new Capillary Transfer Lithography Evaporating toluene Dry PDMS mold 2 w/v% PS PDMS swollen with toluene SAMIM: solvent assisted microcontact molding Dry PDMS mold Toluene 6 nm PS Silk M. K. Gupta, S. Singamaneni, M. McConney, L. F. Drummy, R. R. Naik, V. V. Tsukruk, A Facile Fabrication Strategy for Patterning Protein Chain Conformation in Silk Materials, Adv. Mater., 2010, 22, X (nm) with Scheibel Substrate Chemical pattern ~45 min to allow evaporation of all toluene and removal of PDMS mold Chemical PS pattern S. L. Young, M. Gupta, C. Hanske, A. Fery, T. Scheibel, V. V. Tsukruk, Utilizing Conformational Changes for Patterning Thin Films of Recombinant Spider Silk Proteins, 14 Biomacromolecules, 2012, 13, 3189

15 Counts Counts Counts Counts HFIP FA SAMIM: Mapping Silk Surface Properties a->b b->b 2 Adhesion 2.5 µm 2.5 µm µm Mechanics µm Adhesion, nn Modulus, GPa Adhesion, nn Modulus, GPa

16 SAMIM Patterned C16 Films 200 nm patterning without interfacial cracks Height, nm nm nm Lateral Position, µm 16

17 elastic modulus/max strain Summary of mechanical properties of silk interfacial structures (previous efforts, ) Clay, nanoparticles, crosslinking => 5-fold improvement in modulus In contrast to homopolymers silk is highly heterogeneous multiblock material with coexisting polar, H-bonding, and hydrophobic domains Difficult to find efficient reinforcing components and maximize interfacial interactions E, GPa strain, % silk, 50 nm silk, MeOHsilk, X-linkedsilk-AuNPs silk-sinps silk-agnps silk-claysilk-clay-x-link ultrathin silk interfaces (30-80 nm) E. Kharlampieva, V. Kozlovskaya, B. Wallet, V. V. Shevchenko, R. R. Naik, R. Vaia, D. L. Kaplan, V. V. Tsukruk, Cocrosslinking silk matrices with silica nanostructures for robust ultrathin nanocomposites, ACS Nano, 2010, 4,

hydrophobic-hydrophobic, H- bonding, and polar interactions Graphene oxide 44.1% G, 29.7% A, 12.4% S, 7.

18 Silk-Graphene Oxide Nanocomposites: Nature of Reinforcing Suggestion: explore exfoliated graphene oxide flakes (Hammers method) Strong (E = 250 Gpa vs 1 TPa for graphene), flexible, ultrathin (1 nm), high aspect ration (2000:1), rich functionalities: ALL: hydrophobic-hydrophobic, H- bonding, and polar interactions Graphene oxide 44.1% G, 29.7% A, 12.4% S, 7.5% Y, (GAGAGS) n Silk fibroin M. Chhowalla et al., Nat. Chem. 2010, 2, 1015 Takahashi, Y., et al. (1999) Inter. J. Bio. Macromol., hydrophobic or hydrophilic blocks 18

Organized silk-graphene oxide nanocomposites with extreme

Langmuir-Blodgett deposition Pre-mixed Transfer direction

n D. Kulkarni, I. Choi, S. Singamaneni, V.

19 Organized silk-graphene oxide nanocomposites with extreme properties Initial results: Conventional LbL assembly Langmuir-Blodgett deposition Pre-mixed Transfer direction PHS Air-water interface Graphene oxide sheets (PPS-PAH/GO) n D. Kulkarni, I. Choi, S. Singamaneni, V. V. Tsukruk, Graphene oxide- Polyelectrolyte Membranes, ACS Nano, 2010, 8,

20 Organized silk-graphene oxide nanocomposites with extreme properties Thickness (nm) Fast spin-assisted LbL assembly => prevents aggregation, spread backbones, maximize interactions (d) PS sacrificial layer Silicon μm Number of bilayers 20

21 Silk fibroin absorption on graphene oxide flakes (graphene, mica, silicon oxide) 21

Morphology of silk-graphene oxide nanocomposite and

layered flat GO flakes with uniform surface coverage

individual silk molecules and nanofibrills to

5 μm 70 nm Uniform micromechanical behavior revealed

22 Morphology of silk-graphene oxide nanocomposite and micromechanical testing (a) (b) Topography shows layered flat GO flakes with uniform surface coverage (about 70%) (c) 5 μm 5 μm Preferential binding of individual silk molecules and nanofibrills to graphene oxide flakes and their edges 0.5 μm 70 nm Uniform micromechanical behavior revealed by uniform bulging and organized buckling pattern with the unique wavelength 22

100 50 GO vol.%: 23.5% 11.5% 5.9% 2.9% 0% 0 0.0 0.2 0.

23 Stress (MPa) Micromechanical testing: tensile and compressive properties (d) GO vol.%: 23.5% 11.5% 5.9% 2.9% 0% Strain (%) 10 μm λ=8.2 μm 23

24 Modulus (GPa) Micromechanical testing: outstanding tensile and compressive properties Normalized modulus (GPa) (c) Bulging Buckling Interphase model (bulging) Interphase model (buckling) Halpin-Tsai model (parallel) Halpin-Tsai model (random) Jaeger-Fratzl model Takayanagi model GO (vol%) Takayanagi model: the rule of mixture; Jaeger Fratzl model: nacre materials; Halpin-Tsai models: the 2D fillers All traditional mechanical composite predict significantly lower values than the experimental results - Record values for films: - E = 150 GPA - T = 2.4 MJ/m 3 - Strength = 330 MPa Interphase model value Thickness (nm)

Interphase (not interface) -enhanced reinforcing for strongly interacting components Line of symmetry Interface Silicon PS sacrificial layer GO Interphase GO and silk layers interact strongly through

25 Interphase (not interface) -enhanced reinforcing for strongly interacting components Line of symmetry Interface Silicon PS sacrificial layer GO Interphase GO and silk layers interact strongly through H- bonding, polar, and hydrophobic-hydrophobic interactions Silk backbones are strongly confined and form MOLECULAR REINFORCED INTERPHASE The interphase region extends into the silk where the modulus shows sigmoid decay from 250 GPa to 6 GPa in the bulk silk region Interphase greatly improves the overall modulus of the nanocomposite as an extra enhancement layer Silk Fibroin 0.5 nm 2 to 10 nm A bilayer element of GO-SF Modulus (GPa): 250 The traditional models do not count the interphase presence, so they underestimate the modulus of this nanocomposite 9 25

Young's modulus (GPa) 350 300 250 200 150 100 50 Interphase Model Quantitative Analysis (b) GO region 0 0.0 0.5 1.0 1.5 2.0 GO t (nm) Bulging nm Buckling 2 nm Silk Fibroin 0.

to the interfacial strength τ interphase thickness with E(τ) = (E GO +E SF )/2 For different loading conditions: η is universal scaling parameter reflecting the interfacial interactions Different

26 Young's modulus (GPa) Interphase Model Quantitative Analysis (b) GO region GO t (nm) Bulging nm Buckling 2 nm Silk Fibroin 0.5 nm 2 to 10 nm SF region E *( t) = DE 1+ exp h t + E SF é æ è ç t -1 ö ù ê ø ú ë û E* - current modulus in the interphase ΔE = E GO -E SF t distance from the interface η shape factor; proportional to the interfacial strength τ interphase thickness with E(τ) = (E GO +E SF )/2 For different loading conditions: η is universal scaling parameter reflecting the interfacial interactions Different failure modes of buckling and bulging tests result in different gradiental responses τ varies to reflect the interphase thickness => higher τ results in higher effective modulus = nm single molecular chain dimension A. Kovalev, H. Shulha, M. Lemieux, N. Myshkin, V. V. Tsukruk, J. Mater. Res. 2004, 19,

27 Modulus (GPa) Interphase ( nm) model works well for SF-GO nanocomposites (c) Bulging Buckling Interphase model (bulging) Interphase model (buckling) Halpin-Tsai model (parallel) Halpin-Tsai model (random) Jaeger-Fratzl model Takayanagi model GO (vol%) 27

28 Organized silk-graphene oxide interphase PS sacrificial layer Silicon 28

29 Summary of mechanical properties of silk nanocomposites elastic modulus/max strain silk, 50 nm PLA silk, MeOH silk, X-linked silk-aunps silk-sinps silk-agnps silk-clay silk-clay-x-link silk-go E, GPa strain,% Silk-GO silk nanocomposites 29

30 toughness/strength Summary of mechanical properties of silk nanocomposites and silk interphase material silk, 50 nm PLA silk, MeOH silk, X-linked silk-aunps silk-sinps silk-agnps silk-clay silk-clay-x-link silk-go strength, MPa toughness, kj/m 3 Silk-GO silk nanocomposites 30

Summary of mechanical properties of silk nanocomposite materials Materials contain SF Materials contain GO GO-SF nanocomposite Ultimate stress (MPa): 299 270 250 230

31 Summary of mechanical properties of silk nanocomposite materials Materials contain SF Materials contain GO GO-SF nanocomposite Ultimate stress (MPa): K. Hu, M. K. Gupta, D. D. Kulkarni, V. V. Tsukruk, Ultra-Robust Graphene Oxide-Silk Fibroin Nanocomposite Membranes, Adv. Mater., under revision 31

32 2012 major conclusions AFOSR Program Review 2012 Wetting surface silk layers (for further processing) results in non-uniform swelling with hydrophobically trapped air nanobubbles within swollen silk Gentle micropatterning (a->b, b->b 2 ) allows for 200 nm spatial resolution of surface properties without damaging stresses/properties at interfaces Combining natural interactions (ALL hydrogen bonding, polar, hydrophobic-hydrophobic) of confined silk backbones and graphene oxides results in strong MOLECULAR INTERPHASE ( nm) nanomaterials Strong molecular interphases facilitates ultra-strong GO-SF nanocomposites with record parameters: E = 150 GPa, s = 330 MPa, T = 2.4 MJ/m 3, without increased brittleness (1%) 32

33 FUTURE SEEDS One-pot silk-graphene oxide composites Self-rolling bi-phase silk structures With Kaplan AFOSR Program Review 2012 Arrays of silk nests via inkjet-printing With Kelley-Loughnane 33

34 Knowledge, Technologies, and People Transitions Numerous student exchanges/visits with AFRL and ORNL LbL technology for cell encapsulation to N. Kelley-Loughnane, AFRL Novel scanning twisting thermal probe microscopy mode to T. Bunning, AFRL Vapor-mediated compositional silk patterning to T. Scheibel, U. Bayreuth AFOSR Program Review 2012 Transitioning high-quality researchers Manish Gupta -> M. McAlpine, Princeton 34

35 Meaningful AFOSR/AFRL-related collaborations, WHO WHAT OUTCOME joint ref papers, submitted and published R. Naik, AFRL Metal-binding peptides, silk, 8 student-visits, student co-advisor T. Bunning, AFRL plasma polymerized coatings, 11 student-visits, student co-advisor M. Stone, N. Kelley- Loughnane, AFRL LbL shells for cells, 7 studentvisits, student co-advisor R. Vaia, AFRL Silk nanocomposites, NRs, 2 visits 3 A. Voevodin, AFRL Superphobic surfaces, 2 visits 1 D. Kaplan, Tufts silk constructs, 3 student visits AFOSR Program Review 2012 V. V. Shevchenko, NASU Fery, A., T. Scheibel, U. Bayreuth Silk nanocomposites, 4 visits 3 Silk patterning, 3 visits 1 J. Ankner, ORNL Neutron reflectivity, 5 visits 2 AFOSR NMS&E, AFOSR/AFRL BIONIC Center, AFOSR NDSEG Program 35

Research team, activities, & honors, 2012

2012 Awards/honors/fellowships: Irina Drachuk

36 Research team, activities, & honors, 2012 Graduate students Maneesh Gupta Kesong Hu Seth Young Irina Drachuk (part) Kyle Anderson NDSEG Fellow Katie Campbell AFOSR Program Review 2012 Awards/honors/fellowships: Irina Drachuk SAIC Best Paper Award on LbL silk at ACS Nano

37 Refereed Publications, 2012 Project total, : 10 papers + 1 book M. E. McConney, D. Kulkarni, H. Jiang, T. J. Bunning, V. V. Tsukruk,, A New Twist on Scanning Thermal Microscopy, Nano Lett. 2012, 12, S. L. Young, M. Gupta, C. Hanske, A. Fery, T. Scheibel, V. V. Tsukruk, Utilizing Conformational Changes for Patterning Thin Films of Recombinant Spider Silk Proteins, Biomacromolecules, 2012, 13, C. Ye, I. Drachuk, R. Calabrese, H. Dai, D. L. Kaplan, V. V. Tsukruk, Permeability and Micromechanical Properties of Silk Ionomer Microcapsules, Langmuir, 2012, 28, K. D. Anderson, S. L. Young, H. Jiang, R. Jakubiak, T. J. Bunning, R. R. Naik, V. V. Tsukruk, Plasma Enhanced Co-Polymerization of Amino Acid and Synthetic Monomers, Langmuir, 2012, 28, K. D. Anderson, R. B. Weber, M. E. McConney, H. Jiang, T. J. Bunning, V. V. Tsukruk, Responsive Plasma Polymerized Ultrathin Nanocomposite Films, Polymer, 2012, 53, B. Wallet, E. Kharlampieva, K. Campbell-Proszowska, V. Kozlovskaya, S. Malak, J. F. Ankner, D. L. Kaplan, V. V. Tsukruk, Silk Layering as Studied with Neutron Reflectivity, Langmuir, 2012, 28, R. Suntivich, O. Shchepelina, I. Choi, V. V. Tsukruk, Inkjet-Assisted Layer-by-Layer AFOSR Program Review 2011 Printing of Encapsulated Arrays, ACS Appl. Mater. Interfaces, 2012, 4,

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