Abstracts


Oral Presentations

Bio-related

The State Diagram of SDF-1α-stimulated Tethering, Rolling, and Adhesion of Naïve CD4+ T Lymphoctyes

Nicholas R. Anderson and Daniel A. Hammer

Adhesion to the vascular endothelium through the leukocyte adhesion cascade is a critical step in creating and sustaining an immune response. Previous simulated work from our lab suggests that surface densities on the order of 101 selectin molecules/µm2 and 100 ICAM-1 molecules/µm2 are sufficient for firm adhesion of cells to surfaces. In this work, we show the first experimentally-determined state diagram for the adhesion of naïve CD4+ T lymphocytes. These results show that higher surface densities of both E-selectin and ICAM-1 are required to support firm adhesion of cells. In addition, E-selectin and ICAM-1 were found to have a synergistic relationship in that a small amount of either ligand can compensate for a deficiency in the other. In summary, our results quantitatively map how much of each ligand is needed for leukocyte recruitment, suggesting how the differential expression of endothelial ligands can control cell trafficking and the immune response.

Engineering Bioresponsive Materials from Recombinant Oleosin

Chen Gao and Daniel A. Hammer

Oleosin is a tri-block structural protein that helps stabilizing oil bodies in plant cells. The wild type oleosin found in sunflower seeds is around 200 amino acids long and has a hydrophobic block in the center, with two hydrophilic arms at the N- and C- termini. My work aims to explore various applications of functionalized oleosin, with the help of molecular biology. Targeting nano-particles for drug delivery has great potential for improving efficacy and reducing side effects from systemic toxicity. In particular, the RGD motif has been shown to effectively target the αvβ3 receptor, which is overexpressed in breast cancer cell lines. In addition, new developments in the assembly of materials afford the opportunity to expose cryptic targeting domains in tissue-specific microenvironments in which certain proteases are expressed. Here, recombinant oleosin are designed to combine the responsiveness to environmental proteases with specific targeting. Materials made recombinantly allow complete control over amino acid sequence, in which each molecule is identically functionalized. Previously, oleosin, a naturally occurring plant protein that acts as a surfactant, has been engineered to self-assemble into spherical micelles - a useful structure for drug delivery. In order to make oleosins that are locally activated to bind receptors, oleosin is genetically modified to incorporate the integrin-binding motif RGDS just behind a domain cleavable by thrombin. The resulting modified oleosin self-assembles into spherical micelles in aqueous environments, with the RGDS motif protected by the thrombin-cleavable domain. Upon the addition of thrombin, the RGDS is exposed and the binding of the spherical micelles to breast cancer cells is increased 4-fold. The strategy of combining tissue-specific protease cleavable domains with different adhesive domains is modular, wherein numerous different protease/receptor pairs could be combined to optimize targeting in specific diseases. Current work includes incorporating multiple ligand combinations such as PHSRN and RGDS, enhancing cellular uptake by incorporating cell-penetrating peptides such as Tat-peptide, as well as visualizing oleosin self-assembly under cryo-TEM.

Energy

Preparation of High-Surface Area Active Support by Atomic Layer Deposition

Tzia Ming Onn and Raymond J. Gorte

Active metal oxides play an important role as both catalysts and functional supports. However, a major concern is that their surface areas tend to be low and tend to decrease with usage over time. To create a stable and high-surface area active support, we demonstrate the use of Atomic Layer Deposition (ALD) to disperse thin films of active oxides such as LaFeO3, ceria-zirconia solid solution, CeO2, and Fe2O3 on an Al2O3-based support. These films showed remarkable thermal stability up to 1173 K compared to its respective bulk materials, and when these ALD-prepared composites were used as a support for Pd, they exhibited excellent catalytic performances in CO oxidation, Water-Gas-Shift reaction, and Methane Oxidation.

Reaction pathways for the hydrodeoxygenation of anisole and benzaldehyde over Zn-Pt bimetallic catalysts

Daming Shi, Lisandra Arroyo-Ramírez and John M. Vohs

There is an increasing interest in the use of lignin as a renewable feedstock for the production of high-value aromatic compounds; however, due to its high oxygen content, selective hydrodeoxygenation (HDO) of the aromatic oxygenates produced from lignin depolymerization is required. Metal alloys containing a group 10 metal and a more oxyphillic metal, such as Zn, have been shown to be highly selective for this class of reactions, at least under some conditions. Although, the mechanism by which alloying enhances selectivity is still poorly understood. To provide mechanistic insight, in this study we have investigated the reaction of typical lignin-derived oxygenates, anisole and benzaldehyde, on single-crystal Pt and Zn-Pt model catalysts by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). For Zn-free Pt it was found that anisole and benzaldehyde interact strongly with the surface via the aromatic ring, which promotes undesired ring hydrogenation. Adding Zn to the Pt surface was found to inhibit bonding via the aromatic ring and promoted a stronger interaction with the oxygens. This in turn facilitated selective C-O bond scission without hydrogenating the aromatic ring. These results suggest that Zn-Pt alloys may be an effective catalyst for HDO of lignin-derived aromatic oxygenates with low activity for ring hydrogenation. This hypothesis was then tested and verified by investigating the reaction of anisole with H2 over high surface area carbon-supported Pt and Zn-Pt catalysts.

Zn-Promoted H-ZSM-5 for Endothermic Reforming of Alkanes at High Pressures for Application in Hypersonic Aircraft

Yu-Hao Yeh and Raymond J. Gorte

The addition of Zn to H-ZSM-5 zeolites was studied for application to endothermic reforming in hypersonic aircraft engines. Temperature Programmed Desorption (TPD)/Thermogravimetric-Analysis (TGA) measurements with 2-propanamine on two H(Zn)-ZSM-5 samples showed that at low ion-exchange levels, less than 0.5 Zn/Al, each Zn cation displaces one Brønsted-acid site. Although rates for n-hexane conversion at 633 and 823 K and at a pressure of 137 bar decreased with the loss of Brønsted sites, Zn promotion greatly increased the production of H2 and the formation of small aromatic molecules. FTIR of adsorbed acetonitrile-d3 and calorimetric measurements of adsorbed CO at 195 K indicate that the exchanged Zn cations form Lewis-acid centers. A model in which the Zn cations, acting as Lewis-acid centers, polarize intermediates formed at Brønsted sites is presented as a way of understanding the observations.

Materials

One Step Generation of Salt-Responsive Polyelectrolyte Microcapsules via Surfactant Organized Nanoscale Interfacial Complexation in Emulsions (SONICE)

Gang Duan, Martin F. Haase, Kathleen J. Stebe, Daeyeon Lee

Polyelectrolyte microcapsules have been used for encapsulation and delivery of active agents in various fields, including pharmaceutics, cosmetics, and agriculture. They are widely fabricated using layer-by-layer techniques which are multi-step and time-consuming processes. Here we present an alternative microfluidic process that exploits surfactant organized nanoscale interfacial complexation in emulsion (SONICE) to mass produce uniform functional polyelectrolyte microcapsules with high encapsulation efficiency. Polyelectrolyte microcapsules are templated by water-in-oil-in-water double emulsions. One of the polyelectrolytes is dissolved in the inner aqueous phase while the other is extracted into the organic shell via ion pairing with an oppositely charged hydrophobic surfactant. By carefully tuning the electrostatic interaction between the polyelectrolytes using different inner phase salt concentrations, interfacial complexation is induced at the inner water-oil interface, which results in a few hundred nanometers shell of the SONICE microcapsules. The SONICE microcapsules can be induced to release their cargos upon salt stimulus. Due to the incorporation of hydrophobic surfactants, SONICE microcapsules also have tunable surface hydrophilicity, potentially accommodating a wider variety of active agents. The successful extraction of polyelectrolytes into the organic phase broadens the pallet of polyelectrolytes available for one-step polyelectrolyte microcapsule fabrication, enabling additional functionalities for versatile applications.

Polymer Capillary Rise Infiltration (CaRI) into a Nanoparticle Packing

Jyo Lyn Hor, Yijie Jiang, Haonan Wang, David J. Ring, Robert A. Riggleman, Zahra Fakhraai, Kevin T. Turner, Daeyeon Lee

In this work, we explore the effect of nanoconfinement, polymer-particle interaction, and polymer undersaturation on the polymer infiltration dynamics into a nanoparticle packing based on capillary rise infiltration (CaRI). We thermally anneal a bilayer film of nanoparticle and polymer layers above the polymer glass transition temperature to induce polymer wicking into the nanoparticle packing. Using in situ spectroscopic ellipsometry, we monitor the polymer infiltration process and extract the polymer viscosity based on the Lucas-Washburn model. We observe slowdown in the polymer infiltration, with corresponding increased viscosities and increased glass transition temperatures in nanoconfined polymers relative to the bulk, regardless of polymer-particle interactions. Weakly and strongly interacting polymer-particle pairs differ in exhibiting increased and slightly decreased temperature dependence, respectively. Polymer undersaturation leads to a two-stage filling process – capillary rise, followed by spreading, which enables the generation of compositionally uniform or graded nanoporosity in the polymer-infiltrated nanoparticle films, with tunable morphology and properties with polymer volume fraction. These observations demonstrate crucial material selections in terms of controlling confinement, polymer-particle interactions, and polymer undersaturation for optimal processing conditions and desirable nanocomposite properties.

Path-planning and structure formation inspired by the “lock-and-key” interaction

Yimin Luo, Francesca Serra, Kathleen J. Stebe

We can harvest energy from liquid crystal elastic field to manipulate colloidal motion and form structures. We start by precisely positioning micron-sized, silica colloids with perpendicular anchoring on a wavy wall, at sites of complementary shape. The final position of the colloid depends on the orientation and the type of topological defects. Then by varying the width and depth of the wavy wall geometry, we create a platform that enables manipulation, particle selection, and a detailed study of defect structure under the influence of curvature. The characteristic range of influence is related to curvature of the wall. The distortion can be used to position particles, either in contact with the structure or at a distance. In this rich energy landscape, the particles can find more than one equilibrium positions, and an external field allows them to switch between these metastable states. The external field overcomes energy barriers while the liquid crystal elastic field completes the trajectory. In conclusion, our system does not only allow us to access a scale that traditional manufacturing finds cumbersome, but also manifests richer behaviors such as metasability and reconfigurability.

Polymer infiltration into porous media: the impact of wetting and confinement on chain dynamics

David J. Ring, Rob A. Riggleman, and Daeyeon Lee

Polymer nanocomposites are a class of materials with many unique properties that could be useful for mechanical applications, chemical separation membranes, and electronic properties. Nanocomposites with high fractions of nanoparticles are difficult to make via melt processing, solution casting or layer-by-layer assembly. A promising new method called Capillary Rise Infiltration (CaRI) relies on capillary forces to wick polymers into a dense nanoparticle film. Previous work has shown that low Mw polymer melts infiltrate following the Lucas-Washburn equation for capillary intrusion. The Lucas-Washburn equation predicts that fluids will infiltrate when their contact angle in the pore is less than a critical contact angle of 90 degrees. However, polymers may require stronger driving forces from interfacial tension (a lower critical contact angle) if they lose enough entropy upon entering the pore. Using molecular dynamics, I have been able to probe both confinement and wetting using cylindrical capillaries and simulated nanoparticle packings. This study will reveal the relative importance of polymer-pore interactions and polymer entropy during infiltration, leading to a better understanding of how to make high filler fraction nanocomposites.

Diverse Colloidal Crystals from DNA-grafted Spheres via Self-assembly

Yifan Wang, Ian Jenkins, James McGinley, Talid Sinno, and John Crocker

DNA-grafted colloids are advantageous in making different structure colloidal crystals through self-assembly. In our lab, diverse crystal structures including CsCl, CuAu, NaCl, NiAs, Cu3Ti, Sheared B32, α-IrV, intermedium between different crystal types and partially transformed crystals are prepared through a slowly quenching method, in which temperature goes down as 0.4 degree per hour. Specifically, we coat certain type DNA on to the polystyrene (PS) beads of various sizes through a swelling and de-swelling method. At the same time, another type DNA is coated on to another batch of PS particles that the two type DNA on each particle species could be bond via linker. The DNA type on certain kind PS particles could be either pure or some combinations of the two. We mix two type particles at a certain volume ratio, heat them 5 degrees above the melting temperature of the DNA strands, and then slowly quench them. After the quench, we get nice crystals with good crystallinity which can be observed under optical microscope. By changing the stoichiometry of the two type particles, particle size ratios, as well as the composition of DNA strands on each type particles, we are able to explore new ways of making diverse structure colloidal crystals and get multiple types of crystals in the same sample. Furthermore, the transformation patterns and paths between some crystal types are discussed and mechanisms are well studied. To analyze the crystal structures and measure the exact lattice spacing and bond angles, crystallography can be studied via confocal microscopy.

Poster Presentations

Bio-related

The State Diagram of SDF-1α-stimulated Tethering, Rolling, and Adhesion of Naïve CD4+ T Lymphoctyes

Nicholas R. Anderson and Daniel A. Hammer

Adhesion to the vascular endothelium through the leukocyte adhesion cascade is a critical step in creating and sustaining an immune response. Previous simulated work from our lab suggests that surface densities on the order of 101 selectin molecules/µm2 and 100 ICAM-1 molecules/µm2 are sufficient for firm adhesion of cells to surfaces. In this work, we show the first experimentally-determined state diagram for the adhesion of naïve CD4+ T lymphocytes. These results show that higher surface densities of both E-selectin and ICAM-1 are required to support firm adhesion of cells. In addition, E-selectin and ICAM-1 were found to have a synergistic relationship in that a small amount of either ligand can compensate for a deficiency in the other. In summary, our results quantitatively map how much of each ligand is needed for leukocyte recruitment, suggesting how the differential expression of endothelial ligands can control cell trafficking and the immune response.

CD4+ T lymphocytes persist prior shear flow migratory pattern through VLA-4—VCAM-1 interaction

Sarah Hyun Ji Kim and Daniel A. Hammer

In order for CD4+ T lymphocytes to reach to inflammation sites, CD4+ T lymphocytes depend on expressions of lymphocyte function-associated antigen-1 (LFA-1, αLβ2) and very late antigen-4 (VLA-4, α4β2) to bind to intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), respectively, expressed on blood endothelium. It has recently been shown that CD4+ T lymphocytes exhibit upstream migration against the direction of flow. Using a laminar flow chamber and microcontact printed ICAM-1 and VCAM-1 on PDMS surfaces, we demonstrate that while LFA-1 is responsible for upstream movement, VLA-4-VCAM-1 binding signal is required to persist such migration pattern even after the flow has been removed.

Controlled Liquid-Liquid Phase Transition of Recombinant Oleosin

Ellen Reed and Daniel A. Hammer

Protein engineering enables the creation of materials with designer functionality and responsiveness. In this work, we designed a protein that phase separates into micron sized liquid droplets upon oxidation of a cysteine residue. These droplets are akin to membraneless organelles found naturally in cells. Our work is based on the naturally occurring plant protein, oleosin. Oleosin is amphiphilic with distinct hydrophilic and hydrophobic domains: an N-terminal hydrophilic segment, a highly hydrophobic central core, and a C-terminal hydrophilic segment. From wild type oleosin, a truncated version was engineered that reduced the hydrophobic core from 87 amino acids to 30 and added 5 glycines. Circular dichroism indicates that approximately 65% of the mutant protein is disordered. Intrinsic disorder is a common feature among proteins that form membraneless organelles. A single amino acid mutation was made to introduce a cysteine residue in the hydrophilic arm. Oxidation of this residue results in a dimer. This protein forms micelles above an upper critical solution temperature and form droplets below this temperature. The phase transition is thermoreversible. The addition of a cysteine residue to create a dimer significantly increased the transition temperature of the protein. A family of proteins was synthesized with the single cysteine at various places in the protein backbone. The phase transition temperature can be tuned via the location of the cysteine residue in the protein backbone. Placing the cysteine closer to the N-terminus resulted in a higher transition temperature. At a concentration where the oxidized protein dimer forms droplets but the reduced protein monomer does not, the addition of a reducing agent to break the disulfide bond dissolved the droplets. This protein construct provides a novel way to control protein liquid droplet formation and dissolution. We envision this work having applications as targeted drug delivery vehicle and as a membraneless organelle mimic in synthetic protocells.

Pulsatile Flow in a Microfluidic Model of Arterial Thrombosis

Jason Rossi, Sean Maloney and Scott Diamond

In the majority of studies of thrombosis under flow, blood is perfused at a constant rate – whether an arterial or venous shear rate regime is being interrogated. In reality, blood flow in the arteries is pulsatile in nature, with significant deviations around the mean flow rate in systole and diastole which can even result in flow reversal. To investigate the impact this has on thrombosis in a microfluidic model, a syringe pump was programmed with time-varying flowrate profiles and used to perfuse whole blood to a PDMS microfluidic device, and the resulting platelet accumulation and fibrin formation were studied. PPACK-treated whole blood perfused with 0.5 Hz and 1 Hz triangle waveforms, with a +/- 75% deviation around a 2200 s-1 mean arterial shear rate showed increased platelet accumulation relative to a constant flow rate control. The same waveforms run with CTI-treated whole blood showed no effect on platelet accumulation. For both PPACK and CTI blood, a Fourier power spectrum analysis showed platelet fluorescence signal oscillates with the frequency of the flow waveform whereas fibrin signal showed no significant oscillation. Inclusion of an element of flow reversal in the perfusion waveform resulted in a significant decrease in the amount of fibrin generated. Scaled down versions of the waveforms with mean values in the venous regime (200 s-¹) showed minimal change from the control in either PPACK or CTI blood. In conclusion, pulsatile flow shows differentiation from constant-rate fluid delivery in the arterial regime, particularly in the absence of thrombin.

Soluble Fibrin Causes an Acquired Platelet GPVI-Deficiency: Implications for Coagulopathy

Christopher Verni, Mei Yan Lee, Bradley Herbig, and Scott Diamond

In coagulopathic blood, circulating thrombin may drive platelet dysfunction. Since only 1% conversion of plasma fibrinogen generates 90 nM soluble fibrin (which exceeds ~1 nM GPVI in blood), circulating platelets in coagulopathic blood may display an acquired GPVI-deficiency that impacts hemostasis, even for transfused platelets. Using calcium dye-loaded platelets, the effect of thrombin exposure and soluble fibrin generation on subsequent platelet GPVI function was investigated. Exposure of apixaban-treated platelet-rich plasma (12% PRP) to thrombin (1-10 nM), but not ADP or thromboxane mimetic U46619 exposure, dramatically blocked subsequent GPVI activation by convulxin or collagen-related peptide. The onset of convulxin-insensitivity was time dependent, was not mimicked by exposure to PAR-1/4 activating peptides, was not observed with washed platelets, and was blocked by fibrin polymerization inhibitor (GPRP) or Factor XIIIa inhibitor (T101). PAR-1 signaling through Gaq was not required since vorapaxar blocked thrombin-induced calcium mobilization but had no effect on the ability of thrombin to cause GPVI-deficiency. Convulxin-insensitivity was unaffected by the ADAM10-inhibitor GM6001 and the integrin αIIbβ3 inhibitor GR144053, indicating negligible roles of GPVI shedding and fibrin(ogen)-dependent platelet aggregation, respectively. Thrombin treatment of washed platelets resuspended in purified fibrinogen also produced convulxin-insensitivity that was prevented by GPRP. Exposure of apixaban/PPACK-treated whole blood to thrombin-treated fibrinogen resulted in >50% decrease in platelet deposition in a collagen microfluidic assay due to soluble fibrin assembly. In conclusion, soluble fibrin, rather than thrombin-induced platelet activation through PAR-1 and PAR-4, caused GPVI-deficiency in response to stimuli, and may lead to subsequent hypofunction of endogenous or transfused platelets.

Hemodynamic force triggers rapid NETosis within sterile thrombotic occlusions.

Xinren Yu, Jifu Tan, and Scott L. Diamond

Neutrophils release Extracellular Traps (NETs) made of DNA and various protein components in response to pathogens, cytokines, and danger-associated molecular patterns. Recently intravascular NETs have been implicated in the pathogenesis of sterile thrombosis. Using microfluidics, the effect of shear stress on neutrophils during thrombus formation was studied. Arterial shear caused a marked generation of extracellular DNA as channels approached occlusion while no NETs were detected under venous shear. At the arterial condition, DNA release began almost immediately after neutrophils started accumulating inside the clots. An increase from 100s-1 to 1000s-1 led to rapid DNA release within 2 min indicating that the onset of NET generation was tightly controlled by the hemodynamic forces. NETs generated in response to pathophysiological shear stress might share similar thrombotic or inflammatory properties to NETs formed by other stimuli. Shear-induced NETs may also serve as a biomarker of sterile thrombotic occlusion, particularly in pathologies of arteriole clotting.

Energy

Reaction pathways for the hydrodeoxygenation of anisole and benzaldehyde over Zn-Pt bimetallic catalysts

Daming Shi, Lisandra Arroyo-Ramírez and John M. Vohs

There is an increasing interest in the use of lignin as a renewable feedstock for the production of high-value aromatic compounds; however, due to its high oxygen content, selective hydrodeoxygenation (HDO) of the aromatic oxygenates produced from lignin depolymerization is required. Metal alloys containing a group 10 metal and a more oxyphillic metal, such as Zn, have been shown to be highly selective for this class of reactions, at least under some conditions. Although, the mechanism by which alloying enhances selectivity is still poorly understood. To provide mechanistic insight, in this study we have investigated the reaction of typical lignin-derived oxygenates, anisole and benzaldehyde, on single-crystal Pt and Zn-Pt model catalysts by temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS). For Zn-free Pt it was found that anisole and benzaldehyde interact strongly with the surface via the aromatic ring, which promotes undesired ring hydrogenation. Adding Zn to the Pt surface was found to inhibit bonding via the aromatic ring and promoted a stronger interaction with the oxygens. This in turn facilitated selective C-O bond scission without hydrogenating the aromatic ring. These results suggest that Zn-Pt alloys may be an effective catalyst for HDO of lignin-derived aromatic oxygenates with low activity for ring hydrogenation. This hypothesis was then tested and verified by investigating the reaction of anisole with H2 over high surface area carbon-supported Pt and Zn-Pt catalysts.

Improved Thermal Stability of ZrO2 support by Atomic Layer Deposition

Chao Lin and Raymond Gorte

Ceria and Zirconia films, prepared by Atomic Layer Deposition (ALD) on ZrO2 support (82 m²/g, 773K), greatly improved the thermal stability of the support. Approximately 0.20 g of oxide film was grown on each gram of ZrO2 support, leading to a growth rate of around 0.02 nm per cycle. X-Ray Diffractions and BET surface area measurements confirmed the enhanced thermal stability up to 1073 K., while shrinkage tests showed the ALD-modified samples with increased thermal stability up to 1573 K.

High-Performance SOFC Cathode with Infiltraed LSF-YSZ backbone

Yuan Cheng and Raymond Gorte

Porous composites of Sr-doped LaFeO3 (LSF) and yttria-stabilized zirconia (YSZ) were investigated as conductive scaffolds for infiltrated SOFC cathodes with the goal of producing scaffolds for which only a few perovskite infiltration steps are required to achieve sufficient conductivity. While no new phases form when LSF-YSZ composites are calcined to 1623 K, shifts in the lattice parameters indicate Zr can enter the perovskite phase. Measurements on dense, LSF-YSZ composites show that the level of Zr doping depends on the Sr:La ratio. Because conductivity of undoped LSF increases with Sr content while both the ionic and electronic conductivities of Zr-doped LSF decrease with the level of Zr in the perovskite phase, there is an optimum initial Sr content corresponding to La0.9Sr0.1FeO3 (LSF91). Although scaffolds made with 100% LSF had a higher conductivity than scaffolds made with 50:50 LSF-YSZ mixtures, the 50:50 mixture provides the optimal interfacial structure with the electrolyte and sufficient conductivity, providing the best cathode performance upon infiltration of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF).

Examination of Phosphorus-exchanged Zeolites as Possible Lewis Catalysts

Yichen Ji and Raymond Gorte

Phosphorus-exchanged zeolites can be applied as potential Lewis catalysts, and their functionality have already been proved by reactions such as producing p-xylene through 2,5-DMF and ethylene with high yield. Our studies on those phosphorus-exchanged zeolites mainly focused on the influence of the addition of phosphorus into the zeolites and tried to identify the active sites related to phosphorus on the modified zeolites using our self-build TPD system.

Thermodynamic Studies of Surface Ceria and Ceria-Zirconia Film Prepared by Atomic Layer Deposition on Al2O3

Xinyu Mao and Raymond Gorte

The thermodynamic properties of surface ceria and surface ceria-zirconia were investigated through equilibrium isotherms of ceria films and ceria-zirconia films on alumina support. These films were prepared by Atomic Layer Deposition. Oxidation isotherms between 873K and 1073K were determined by flow titration and coulometric titration in the equilibrium of H2O and H2. Compared to pure ceria powders, surface ceria and surface ceria-zirconia have shown higher reducibilities in all cases. At 1073K, the flow titration and coulometric titration together showed a continuous reduction for surface ceria from CeO2 to CeO1.55 at P(O2) from 1 atm to 10-21 atm. Between 873K and 1073K, a sharp change of oxidation state of ceria-zirconia on alumina support prepared using ALD has been observed in the oxidation isotherms determined by coulometric titration.

Structure - Activity Relationships for Thermal and Photocatalytic Reactions Using Well-Defined TiO2 Nanocrystals

Paul Andrew Pepin, John M. Vohs

TiO2 is a prototypical catalyst for selective thermal and photo-oxidation of organic molecules. In order to probe the impact of nanocrystal surface structure and crystallite size, TiO2 nanocrystals of well-controlled size and shape were cast into thin films and studied using SEM and temperature programmed desorption (TPD) of acetaldehyde in an ultra-high vacuum chamber. The TiO2 nanocrystals demonstrated activity for both thermal- and photo-catalytic pathways for acetaldehyde. TPD experiments revealed that the thermal and photo-chemical pathways for acetaldehyde have dependencies on surface structure and crystallite size and activities may be tuned by controlling both shape and crystallite size. These results of this study demonstrate the utility of using model catalyst systems of well-controlled geometries to determine the influence of nanocrystal shape and structure on catalytic activity.

Selective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol over PtWOx/C catalysts

Cong Wang and Raymond J. Gorte

Tetrahydrofurfuryl alcohol (THFA) is one of the key biomass-derived intermediates that can be manufactured by total hydrogenation of furfural in large scales. Hydrogenolysis of THFA that selectively cleaves the C-O bond in the cyclic ether ring has drawn substantial attentions due to the production of 1,5-Pentanediol (1,5-PeD.) 1,5-PeD is one of the key monomers to produce polyesters and polyurethanes. ReOx and MoOx modified Rh and Ir catalysts have been reported to achieve high yields and selectivities from THFA towards 1,5-PeD. In this study, a systematic catalyst screening is conducted for the production of 1,5-PeD. The experiments are performed in a high pressure continuous flow reactor to elucidate the reaction routes. They are mainly conducted at 200C, 36 bar and WHSV = 36 h-1 over 10-wt% Metal 5-wt% Metal Oxide/C (M1M2Ox/C.) Among various combinations in the screening, PtWOx/C showed high activity and selectivity. The effects of tungsten leaching, multi-valence oxides, and the solid acidity are evaluated over the Pt-WOx/C catalyst.

Computational Studies of Perovskite Oxides for Oxygen Reduction & Evolution

Liang Zhang and Aleksandra Vojvodic

Given the crucial role of catalysis science in our current society, understanding how to improve and design new catalysts for desired reactions with optimal catalytic activity and selectivity using minimum energy is a grand challenge. In this presentation, we show how atomic-level computational studies can help develop a fundamental and detailed understanding of the relationship between the atomic scale structure of the catalyst and its function. We provide a general guideline for designing efficient perovskite-based catalysts with smaller loading of noble metals and improved stability. The focus will be on the following chemistries:
1. Mechanistic study of oxygen incorporation on LaxSr1-xFeO3- for solid state fuel cells
2. Activation of SrTiO3 by heterostructure engineering for electrochemical water splitting.

Materials

Path-planning and structure formation inspired by the “lock-and-key” interaction

Yimin Luo, Francesca Serra, Kathleen J. Stebe

We can harvest energy from liquid crystal elastic field to manipulate colloidal motion and form structures. We start by precisely positioning micron-sized, silica colloids with perpendicular anchoring on a wavy wall, at sites of complementary shape. The final position of the colloid depends on the orientation and the type of topological defects. Then by varying the width and depth of the wavy wall geometry, we create a platform that enables manipulation, particle selection, and a detailed study of defect structure under the influence of curvature. The characteristic range of influence is related to curvature of the wall. The distortion can be used to position particles, either in contact with the structure or at a distance. In this rich energy landscape, the particles can find more than one equilibrium positions, and an external field allows them to switch between these metastable states. The external field overcomes energy barriers while the liquid crystal elastic field completes the trajectory. In conclusion, our system does not only allow us to access a scale that traditional manufacturing finds cumbersome, but also manifests richer behaviors such as metasability and reconfigurability.

One Step Generation of Salt-Responsive Polyelectrolyte Microcapsules via Surfactant Organized Nanoscale Interfacial Complexation in Emulsions (SONICE)

Gang Duan, Martin F. Haase, Kathleen J. Stebe, Daeyeon Lee

Polyelectrolyte microcapsules have been used for encapsulation and delivery of active agents in various fields, including pharmaceutics, cosmetics, and agriculture. They are widely fabricated using layer-by-layer techniques which are multi-step and time-consuming processes. Here we present an alternative microfluidic process that exploits surfactant organized nanoscale interfacial complexation in emulsion (SONICE) to mass produce uniform functional polyelectrolyte microcapsules with high encapsulation efficiency. Polyelectrolyte microcapsules are templated by water-in-oil-in-water double emulsions. One of the polyelectrolytes is dissolved in the inner aqueous phase while the other is extracted into the organic shell via ion pairing with an oppositely charged hydrophobic surfactant. By carefully tuning the electrostatic interaction between the polyelectrolytes using different inner phase salt concentrations, interfacial complexation is induced at the inner water-oil interface, which results in a few hundred nanometers shell of the SONICE microcapsules. The SONICE microcapsules can be induced to release their cargos upon salt stimulus. Due to the incorporation of hydrophobic surfactants, SONICE microcapsules also have tunable surface hydrophilicity, potentially accommodating a wider variety of active agents. The successful extraction of polyelectrolytes into the organic phase broadens the pallet of polyelectrolytes available for one-step polyelectrolyte microcapsule fabrication, enabling additional functionalities for versatile applications.

Lens-shaped Particles for Stabilization of Biphasic Systems

Wei-Han Chen, Fuquan Tu, Laura Bradley and Daeyeon Lee

Anisotropic particles are found to be effective solid stabilizers in biphasic systems. We develop a new scalable synthesis method to produce lens-shaped particles with uniformity and shape tunability for investigating the effect of particle shapes on water-hexadecane emulsification. Large amount of lens-shaped particles are prepared by seeded emulsion polymerization, including biconvex, plano-convex, and concavo-convex series, which depend on the interfacial tensions in intermediate Janus structures. Interestingly, biconvex particles were found to stabilize water-in-oil emulsions, whereas hemisphere-like concavo-convex particles tended to stabilize the opposite oil-in-water emulsions. We also proposed toluene reshaping and layer-by-layer coating to confirm surface chemistry is not the key factor to determine the type of emulsions. These results inspire us to further investigate how geometries of particles influence surfactancy and stability of emulsions. By precisely controlling the curvatures on two sides of lens-shaped particles, we can utilize the shape of particles, rather than surface chemistry, to control emulsion types and effectiveness in emulsification.

Bicontinuous biphasic emulsion gels for catalysis and separation applications

Giuseppe Di Vitantonio, Daeyeon Lee, and Kathleen J. Stebe

Simultaneous operation of catalysed reaction and separation had transformative impact increasing the efficiency of chemical processes; very successful particle-stabilized emulsion-based phase-transfer catalysis has been developed, however the traditional water in oil/oil in water emulsion cannot perform a steady and robust separation of the product. A bicontinuous particle-stabilized emulsion (bijel) can overcome this limitations, in our lab we developed the solvent-transfer induced phase separation (STRIPS) technique to produce such material in a simple, flexible and continuous fashion. In the first part of our study we use this soft material to run simultaneous extraction and reaction in which oil soluble reactants are continuously removed from the oil domains, undergo hydrolysis and partition in the water phase. In the second set of experiments water soluble reactants undergo homogeneously catalysed carbon-carbon bond formation becoming hydrophobic and thus move in the oil domains of the bijel scaffold. As final part the chemistry of the nanoparticles composing the particle-stabilized emulsion is modified to accommodate catalytic species and perform heterogeneously catalysed carbon-carbon bond reactions in which, again, water soluble chemicals react generating hydrophobic species.

Structural signatures of shear banding in confined polymer pillars

Robert J.S. Ivancic and Robert A. Riggleman

Under confinement, amorphous materials exhibit interesting mechanical properties which are not well understood. Phenomenological models explain these properties by postulating an underlying defect structure in these materials. Using machine learning methods, we identify mesoscale defects that lead to shear banding in confined polymer pillars well below the glass transition temperature. We successfully apply these methods to pillars of diameters of 12.5, 25, 50, and 100 particle diameters. Our results show that some of the primary structural features responsible for shear banding on this scale are fluctuations in the diameter of the pillar. Surprisingly, these fluctuations are quite small compared to the diameter of the pillar, only half of a particle diameter in size.

An Advanced Sampling Method for Studying Self-Assembly

Zhitong Jiang and Amish Patel

The self-assembly of amphiphilic molecules into mesostructures, such as micelle, bilayer and vesicles, is important in many applications, including materials synthesis, drug delivery, and separations. Molecular simulations play an important role in connecting the molecular characteristics of the amphiphilies to the properties of these mesostructures and transitions between them. However, using straightforward simulations to study them can be challenging, due to the large separation in timescales between the relaxation of individual molecules and the nanostructures. Here, we present an enhanced sampling method to address this challenge. Our approach involves organizing the amphiphilic molecules of interest into structures with well-defined symmetries, through the application of an external potential, which biases Fourier components of the molecular density field. The response of the system to the biasing potentials allows us to estimate mesostructure’s properties, as well as the thermodynamic stability of a particular mesophase with respect to another.

A novel method to characterize optical properties of disordered meta-materials based on ellipsometry

Chen Li, Ethan Glor, Robert Ferrier, Melissa Vettleson, Russell Composto, Zahra Fakhraai

Polymer/noble metal nanocomposites are of interest for various applications due to their interesting optical and mechanical properties. In composite thin films, characterizing properties such as nanoparticle dispersity, orientation of anisotropic particles, and the degree and orientation of aggregation is important in predicting materials properties. However, techniques to readily characterize these properties are limited. Here, we use ellipsometry to characterize the properties of nanocomposite thin films of polymer/gold nanorod. The optical properties of the nanorod are modeled as an effective index of refraction for a disordered meta-material. This effective medium index is then related to the longitudinal surface plasmon resonance (LSPR) of the nanorods. The degree of birefringence in the LSPR frequency, as determined by variable angle ellipsometry measurements, can help determine the average orientation of the rods in the thin film as well as the degree of aggregation. With this method, one can quickly and accurately define the average orientation and average aggregation of nanorods within a nanocomposite with a single measurement, with accuracy much beyond what is available using a combination of UV/Vis and TEM measurements. Ellipsometry also allows us to perform in-situ variable temperature measurements to monitor properties such as nanoparticle shape and the glass transition temperature of the matrix in ultra-thin films of nanocomposites. This technique can also be used in a variety of applications such as temperature sensing and sensing applications such as hydrogen sensing.

Robust Superhydrophilic Coating through Assemblies of Polymer Grafted Silica Nanochains

Zhiwei Liao, Gaoxiang Wu, Daeyeon Lee, and Shu Yang

There have been significant efforts to create membranes for oil/water separation due to its high selectivity and energy efficiency; however, preventing membrane fouling while enabling scalable and economical manufacturing of such membranes remains a major challenge. In this work, we demonstrated a method to create a robust superhydrophilic coating that repels oil underwater by controlling surface chemistry and structure. These membranes were fabricated by synthesizing poly(acrylic acid)-grafted SiO2 nanochains, and subsequently spraying coating them onto substrates. The sprayed nanochains assemble to form a coating with nanoscale roughness and porous structure. The wetting properties of these coatings are compared to non-coated substrates, spherical SiO2 nanoparticle coatings, and SiO2 nanochain coatings without the polymer grafting. Beside demonstrating superhydrophilicity (water contact angle ≈ 0°) and underwater superoleophobicity (oil contact angle underwater ≥ 165°), the resulting coating shows significantly lower contact angle hysteresis (< 1°) and adhesion hysteresis (≈ 0.2 mN/m) than other samples, demonstrating an extremely low oil adhesion. Even after the coating was fouled with oil, it can lift and detach the oil from the surface in less than 20 seconds when exposed to water whereas other surfaces take much longer for oil dewetting to occur or no dewetting was induced at all. Our approach demonstrated here is a facile yet effective method to fabricate robust underwater superoleophobic coating, showing a promising future for adding antifouling features onto separation membranes.

A novel approach to understand ductile to brittle transition in glass forming polymer systems during deformation

Emily Y. Lin, Robert A. Riggleman

Glassy polymer systems are used in a wide array of industrial applications. Understanding the load bearing properties and failure mechanisms during deformation is critical to improve design of new materials. Specifically, understanding the temperature driving ductile to brittle transition allows for greater control of the material properties for applications in which the operating temperature varies significantly. Recent studies on the topic of deformation in disordered systems showed that clusters of extreme strain localization (i.e. shear transformation zones, STZ) form and organize into shear band, at which failure occurs. However, standard Lennard Jones (LJ) pair potential used ubiquitously in the bead-spring model are shown to be ductile even at temperatures far below the glass transition temperature. By compressing the LJ potential, we can increase the elastic free energy, which is related to the curvature of the potential, and decrease the interfacial free energy, which is related to the overall system energy density, we can cross over the energy barrier for the formation of a new surface. In this study, we first examined the characteristics of this modified LJ (mLJ) model using cylindrical nano pillars made from short chain polymers, and we showed that the mLJ model can indeed produce brittle failure. Then we track the correlation of STZ regions during deformation to help elucidate the changes in behavior of glassy polymer systems using a novel parameter, Sl, to quantify ductile to brittle transition induced by increase in temperature.

Equilibrium and Dynamic Field Theoretic Simulations of Polymer Nanocomposites

Ben Lindsay, Huikuan Chao, Rob Riggleman

Polymer nanocomposites (PNCs) are an exciting class of materials in which nanoparticles are dispersed in a polymer matrix. PNCs have been shown to exhibit novel combinations of enhanced mechanical, thermal, electrical, and optical properties. The specific property enhancements and the directionality of those enhancements depends strongly on spatial control of the nanoparticles. Studying these materials experimentally can be expensive and time-consuming, in large part because of the vast array of parameters that impact the spatial distribution of nanoparticles. Simulations based on the Self-Consistent Field Theory (SCFT) framework have been shown to enable efficient exploration of mesoscale polymer systems, but they traditionally do not allow the incorporation of nanoparticles. Our lab has built on the SCFT framework to implement equilibrium and dynamic field theoretic simulations of PNCs, enabling us to both interpret and guide experimental research in advanced PNC materials. Our simulations demonstrate that a delicate balance between the entropy of both the grafted chains and the matrix chains plays a key role in the dispersion and controlled self-assembly of many PNC systems.

Diverse Colloidal Crystals from DNA-grafted Spheres via Self-assembly

Yifan Wang, Ian Jenkins, James McGinley, Talid Sinno, and John Crocker

DNA-grafted colloids are advantageous in making different structure colloidal crystals through self-assembly. In our lab, diverse crystal structures including CsCl, CuAu, NaCl, NiAs, Cu3Ti, Sheared B32, α-IrV, intermedium between different crystal types and partially transformed crystals are prepared through a slowly quenching method, in which temperature goes down as 0.4 degree per hour. Specifically, we coat certain type DNA on to the polystyrene (PS) beads of various sizes through a swelling and de-swelling method. At the same time, another type DNA is coated on to another batch of PS particles that the two type DNA on each particle species could be bond via linker. The DNA type on certain kind PS particles could be either pure or some combinations of the two. We mix two type particles at a certain volume ratio, heat them 5 degrees above the melting temperature of the DNA strands, and then slowly quench them. After the quench, we get nice crystals with good crystallinity which can be observed under optical microscope. By changing the stoichiometry of the two type particles, particle size ratios, as well as the composition of DNA strands on each type particles, we are able to explore new ways of making diverse structure colloidal crystals and get multiple types of crystals in the same sample. Furthermore, the transformation patterns and paths between some crystal types are discussed and mechanisms are well studied. To analyze the crystal structures and measure the exact lattice spacing and bond angles, crystallography can be studied via confocal microscopy.

Solvent-driven infiltration of polymer (SIP) into nanoparticle packings

Neha Manohar, Kathleen Stebe, and Daeyeon Lee

Infiltrating polymers into the interstices of nanoparticle packings offers a new opportunity to create composites with extremely high fractions of nanoparticles (> 50 vol%) and circumvents the challenge of processing composites by dispersing or mixing nanoparticles into polymers. These polymer-infiltrated nanoparticle films (PINFs) have high strength and toughness and also exhibit high scratch and wear resistance, making them ideal protective and structural coatings. Previous attempts to infiltrate polymer into porous structures and nanoparticle packings have involved cumbersome, lab-scale techniques that can require abrasive processing conditions, which lead to low loadings or inhomogeneous and low molecular weight polymer fillings. Herein we propose a one-step, room temperature method for PINF fabrication through solvent-driven infiltration of polymer (SIP) into nanoparticle packings from a bilayer film composed of a densely packed layer of nanoparticles coated on top of a base polymer film. Upon solvent vapor exposure, capillary condensation occurs in the nanoparticle packing, leading to plasticizing of the polymer layer. This results in a composite layer on top that has an extremely high filler fraction without the need for any energy-intensive processing techniques. The SIP technique can be controlled by tuning solvent quality and molecular weight, and a poor solvent regime was discovered that can be exploited to obtain PINFs from dip-processing.

Solvent-driven infiltration of polymer (SIP) into nanoparticle packings

Christopher L. Porter, Young K. Lee, Scott L. Diamond, Talid R. Sinno, John C. Crocker;

Flows containing time-dependent adhesive particles appear in a wide variety of problems in science and engineering. In biology, particularly in clotting and leukocyte migration, these problems are particularly challenging to fully understand and simulate, as there are intricate chemical signaling pathways which alter adhesion properties, particles undergo morphological changes, and complex flow fields emerge with particle deposition and aggregation. Here we present a model experimental system to explore the kinetics and resulting structure of particle adhesion for a range of shear rates and bulk particle concentrations. This system uses DNA to mediate particle-surface and particle-particle interactions. We show that the resulting kinetics of monolayer formation can be empirically described by a generalized random sequential adsorption with blocking model. Interestingly, structural analysis of the resulting monolayers indicates that at high particle Peclet numbers, hydrodynamic shielding effects inhibit deposition downstream of already deposited particles. Additionally, the use of this system in particle aggregation and particle rolling experiments will be discussed.

Polymer Behavior Under Rigid Symmetric Confinement

James F. Pressly, Ronald L. Jones, Robert A. Riggleman, and Karen I. Winey

Polymers are subjected to nanoconfinement in a wide range of applications and industries, including nanoscale lithography in semiconductor manufacturing, natural gas extraction, and polymer nanocomposites. In each instance, the confinement of the polymer alters the chain conformation and the chain dynamics. A better understanding of the relationship between confinement and polymer behavior will allow for faster innovation in these fields as they will no longer be slowed down by lengthy trial and error studies. Many previous studies of confined polymer behavior have been limited in their ability to measure conformational changes and changes in large scale diffusion. Confined polymer conformation studies have been limited to measuring thin films with a free surface and only in directions parallel to the confining surfaces, which has been shown to be less altered by changes in confinement than the perpendicular direction. Studies of confined polymer dynamics typically measure segmental dynamics and use scaling laws to determine a diffusion coefficient, leading to conflicting results between studies. Here, we present our work addressing the limitations of these previous studies. A unique sample geometry allows us to simultaneously probe confined polymer conformations parallel and perpendicular to the confining surfaces using small angle neutron scattering. Additionally, we use elastic recoil detection to measure polymer diffusion over 100s of nanometers to more accurately determine the diffusion coefficients of confined polymers.

Microfluidic-Based Protein-Stabilized Microbubbles for Ultrasound Antivascular Therapy

Katherine W. Pulsipher, Harim Jeon, Weiwei Meng, Chen Gao, Daniel A. Hammer, Daeyeon Lee, Chandra M. Sehgal

Microbubbles are often used as ultrasound contrast agents due to their high compressibility, while microbubbles below 10 m in size can also convert acoustic energy into heat, with application in antivascular treatment for cancer. Current understanding of how microbubble properties affect ability to function in both areas is limited. We have used simulations of bubble ensembles to predict bubble behavior with varying bubble diameter, mechanical properties, and insonation frequency. Generating microbubbles to match these characteristics with high monodispersity is challenging using conventional methods such as sonication. We have developed a single layer polydimethylsiloxane-based flow-focusing microfluidic device with an air-actuated valve, to generate stable (little change in size over 20 days), monodisperse (Cv <5%) bubbles. A mixture of recombinant protein oleosin and triblock copolymer poly-(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) form the bubble shell, with both components necessary for stability. Decreasing the length of the hydrophilic PEO blocks leads to a softening of the shell. We have also developed an all-in-one bubble generation and testing microfluidic device to test the stability of microbubbles under ultrasound and to validate predicted heating enhancement with varying bubble characteristics.

Nanoblend infiltrated nanoparticle films via Solvent Driven Infiltration of Polymers and Photo-polymerization

Yiwei Qiang, Neha Manohar, Kathleen J. Stebe, Daeyeon Lee

Polymer Blending is an appealing strategy to generate high-performance materials which combine the excellent properties of individual polymers. However, most polymers are incompatible with one another and tend to phase separate unless they are compatibilized. Compatibilizers such as copolymers or nanoparticles are either difficult to synthesize or their chemical compositions need to be carefully designed. Physical effect of confinement has been shown to increase the miscibility of polymer blends in polymer blends ultrathin films. Here, we present a novel composite film that is composed of polymer blends and nanoparticles to study the effect of confinement on the miscibility of polymer blends. The fabrication of the composite film involves first generating a bilayer film of a nanoparticle layer atop a polymer layer. Then the bilayer film is exposed to monomer which is a good solvent for the polymer and condensed monomer in the nanoparticle layer can induce the infiltration of the bottom polymer layer into nanoparticle interstices. UV exposure is later adopted to polymerize the monomers, thus forming a polymer blend filling the voids of nanoparticle packing. We demonstrate this process using a model polystyrene (PS)/silica nanoparticle bilayer film system and two different monomers, methyl methacrylate (MMA) and n-butyl acrylate (n-BA). Using in-situ ellipsometry, we found that the volume fraction of PS can be adjusted by controlling the ratio of the original thickness of PS layer to nanoparticle layer and the volume fraction of another polymer (PMMA or PnBA) can be varied by controlling UV exposure duration.

Investigating the thermodynamics of conformational flexible solutes with Dynamic Indirect Umbrella Sampling

Nick Rego and Amish Patel

The solvation of conformationally flexible solutes is ubiquitous, and a rigorous understanding of the thermodynamics of this process is invaluable to understanding phenomena in fields ranging from biochemistry to polymer physics. However, the nature of coupling between hydration and conformational degrees of freedom is complex and remains an active area of computational and experimental research. Here, we use explicit solvent molecular dynamics simulations to investigate the hydration of methyl-capped dipeptides – small, flexible systems that nevertheless exhibit complex and interesting behavior. We employ a two-pronged approach to simultaneously investigate the solvent and solute degrees of freedom. We use our Dynamic Indirect Umbrella Sampling (Dynamic INDUS) to control the hydration levels of flexible solutes. Using a combination of Dynamic INDUS and existing enhanced sampling methodologies (Weighted Ensemble) to probe solute degrees of freedom, we have constructed the free energy landscape of alanine dipeptide as a function of both conformational and solvent coordinates. This combined approach provides a valuable window into the interplay between hydration and conformational flexibility for complex peptide and protein systems, and has the potential to offer valuable insight into the role of water in the thermodynamics of biomolecular interactions. Furthermore, Dynamic INDUS can be used to efficiently and rigorously calculate the free energetics of emptying out hydration shells of flexible solutes. By combining it with appropriate thermodynamic cycles we demonstrate its utility in computing hydration free energies of flexible solutes. We demonstrate this approach on blocked dipeptide systems.

Dynamics of Solvent Induced Infiltration of Polymers into nanoparticle packing

R Bharath Venkatesh, Neha Manohar, Tianren Zhang, Daeyeon Lee, Robert Riggleman, Kathleen Stebe

Polymer Nanocomposite synthesis methods are usually focussed on dispersion of nanoparticles in the polymer matrix with the aid of a solvent which is later evaporated. This method suffers from the problems of phase separation and aggregation of the nanoparticles from the polymer matrix. Recently, the Lee lab has developed a solvent driven infiltration approach to create dense, stable nanocomposites using solvents wetting the nanoparticle packing to drive the polymers into the spaces between the nanoparticles. The SIP(Solvent induced Infiltration of Polymer) process is along the same lines as the previous work done in our lab where thermal annealing was used to drive the polymer from a melt into the packing(CARI). Molecular dynamics simulations of the coarse grained model of the system are used to study the infiltration in the presence of a solvent. The mechanism of this infiltration and the influence of solvent quality, entanglement of polymers, etc. on this process are determined from MD simulations. Specifically, we would like to find a surface-driven regime, defined by the interaction of the nanoparticle with the polymer, at which the polymer advances into the nanoparticle layer by adhesion to the particle surface. The poster will illustrate the models and methods used in the simulations and discuss our findings.