WorldCat Identities

Granick, Steve

Overview
Works: 40 works in 43 publications in 1 language and 51 library holdings
Roles: Author
Publication Timeline
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Most widely held works by Steve Granick
Mechanical probes of equilibrium and non-equilibrium entanglement effects in tailor-made polymer networks by Steve Granick( )

3 editions published in 1982 in English and held by 5 WorldCat member libraries worldwide

Molecular Simulations of Ultrathin Perfluoropolyether Films under Shear( Book )

2 editions published in 1997 in English and held by 2 WorldCat member libraries worldwide

In this project dealing with aqueous films confined between solid surfaces at spacings comparable to the molecules themselves, we succeeded, for the first time, to investigate the effect of deformation frequency and amplitude on the shear dynamics of these films. We also succeeded, for the first time, to observe molecular ordering of aqueous ions at the solid-liquid interface. These unique experiments not only open new directions in research on liquids in confined geometries, but also have important implications for the field of tribology
Statistical mechanical theory of structure and miscibility of polymer nanocomposites: Effects of density, filler shape, and chemical heterogeneity by Lisa M Hall( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Motivated by increasing interest in various types of nanoparticles or fillers added to polymers to enhance the material properties, the Polymer Reference Site Interaction Model (PRISM) theory is applied to study the structure and miscibility of polymer nanocomposites (PNCs). Spherical fillers are studied in homopolymers of varying density and interfacial interaction strengths, with specific favorable comparisons to experimental scattering results. Also discussed briefly are copolymers composed of two types of monomer which interact differently with the filler. The polymer induced depletion attraction is dominant and causes phase separation if interfacial attractions are weak. Complete miscibility can be achieved at moderate interfacial attraction strengths, due to a sterically stabilizing bound polymer layer. The bound layer remains with a strong interfacial attraction, but phase separation is induced by polymer bridging between nanoparticles. For copolymers, the bridging attraction is strongly affected by chemistry and monomer spatial arrangement (random versus alternating). The effect of nanoparticle dimensionality is explored by comparing rod, disk, and cube shaped fillers. Nanoparticle interactions on several length scales are relevant in the depletion regime. The bound polymer layer present in the miscible and bridging regimes damps out order on these length scales in favor of increased order on an averaged filler length scale. The effect of nanoparticle chemical heterogeneity was briefly explored by investigation of fillers composed of two tangentially connected spheres with different polymer interfacial attraction strengths or with an added inter-nanoparticle site-site attraction. Such heterogeneous diatomic fillers exhibited additional structural features and particle clustering compared to analogous homogeneous nanoparticles. Motivated by recent experimental interest in carbon nanotubes, thin rod particles were further investigated. Adding a strong rod-rod attraction relevant to nanotubes predictably leads to a strongly attractive potential of mean force at contact, especially when there is little bound polymer. In the stabilized and bridging regimes, miscibility can persist until a stronger rod-rod attraction if it is of shorter spatial range than the polymer-rod interfacial attraction. An initial investigation of these attractive rods in a random copolymer revealed that replacing the homopolymer with copolymer can significantly reduce miscibility
Interactions of disruptive materials with phospholipid bilayers by Andrew S Campbell( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

The eukaryotic cell membrane is a complex mixture of cholesterol, lipids, and proteins. Direct study of the cell membrane must include these multiple variables, which significantly complicates their analysis. Model systems minimize the number of components used in a membrane study. Atomic force microscopy (AFM) can be employed to study the morphology of model supported phospholipid bilayers (SLB). Thermal and diffusive properties of membranes are identified using differential scanning calorimetry (DSC) and fluorescence correlation spectroscopy (FCS). Attenuated total reflectance infrared spectroscopy (ATR-FTIR) can be applied to observe SLB disruption. This suite of techniques has been used to observe interactions of molecules interfering with phospholipid bilayers. Single- and multicomponent SLBs and phospholipid vesicles are employed as models of cell membranes. The effects of the pore-forming peptide alamethicin are shown for lipid bilayers with varying compositions. A correlation between the presence of sphingomyelin or cholesterol and increased pore formation is identified by the increase of potassium leakage through vesicles and formation of raft structures visible with AFM. ATR-FTIR shows that alamethicin disrupts all types of bilayers studied, suggesting that the observed effects are directly correlated to alamethicin incorporation. A comparison is made between the interactions of two polychlorinated biphenyl isomers and an SLB. A study of AFM micrographs identifies multiple phase transitions in one isomer, but only one phase transition for the other isomer. Two transitions are consistent with an uninterrupted bilayer, but one transition suggests that an intercalated molecule ties the bilayer leaflets together, or a contaminant molecule disrupts substrate ordering on the bilayer. DSC results show that one isomer is more strongly associated with the bilayer than the other isomer, a difference that is explained based on geometric differences in the isomers. FCS is employed to observe a PCB-lipid complex which highlights the different strengths of interaction between PCB isomers and lipids. A model is proposed where the ortho-substituted PCB isomer inserts into the bilayer and strongly associates with the hydrophobic region. In contrast, the planar PCB isomer does not insert deeply past the hydrophilic region of the bilayer, which allows it to interrupt interactions between the substrate and its closest bilayer leaflet. We employ atomic force microscopy to show interactions of sphingomyelin or cholesterol with a mixed DSPC/DOTAP bilayer. We report that sphingomyelin, but not cholesterol, supports the formation of hexagonal crystalline domains. These domains are small (ca. 70 nm) and can be observed with AFM as high as 40°C. We use differential scanning calorimetry of DSPC/DOTAP vesicles in the presence of either sphingomyelin or gramicidin A to show the elimination of one thermogram peak. This result suggests that sphingomyelin, like gramicidin A, interacts with both leaflets in the bilayer. We report dichroic ratios measured from each bilayer composition with ATR-FTIR. The methylene dichroic ratios in all bilayers decrease with introduction of both SM and Chol, but the magnitude of decrease is greater in the presence of SM. A decrease in methylene dichroic ratios is related to an increase in lipid chain order. We propose that SM exerts extensive hydrogen-bonding forces on DSPC and sustains structure to high temperatures when incorporated in a 40 mol% ratio. At this same temperature, we propose that Chol does not support the same structure formation because it induces the liquid-ordered phase in DSPC/DOTAP. We note that sphingomyelin promotes multilayer, not bilayer, formation
Single particle motion of polymeric, colloidal, and biological materials by Stephen M Anthony( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Small particles and their dynamics are of widespread interest due both to their unique properties and their ubiquity. Here, we investigate several classes of small particles: colloids, polymers, and liposomes. All these particles, due to their size on the order of microns, exhibit significant similarity in that they are large enough to be visualized in microscopes, but small enough to be significantly influenced by thermal (or Brownian) motion. Further, similar optical microscopy and experimental techniques are commonly employed to investigate all these particles. In this work, we develop single particle tracking techniques, which allow thorough characterization of individual particle dynamics, observing many behaviors which would be overlooked by methods which time or ensemble average. The various particle systems are also similar in that frequently, the signal-to-noise ratio represented a significant concern. In many cases, development of image analysis and particle tracking methods optimized to low signal-to-noise was critical to performing experimental observations. The simplest particles studied, in terms of their interaction potentials, were chemically homogeneous (though optically anisotropic) hard-sphere colloids. Using these spheres, we explored the comparatively underdeveloped conjunction of translation and rotation and particle hydrodynamics. Developing off this, the dynamics of clusters of spherical colloids were investigated, exploring how shape anisotropy influences the translation and rotation respectively. Transitioning away from uniform hard-sphere potentials, the interactions of amphiphilic colloidal particles were explored, observing the effects of hydrophilic and hydrophobic interactions upon pattern assembly and inter-particle dynamics. Interaction potentials were altered in a different fashion by working with suspensions of liposomes, which, while homogeneous, introduce the possibility of deformation. Even further degrees of freedom were introduced by observing the interaction of particles and then polymers within polymer suspensions or along lipid tubules. Throughout, while examination of the trajectories revealed that while by some measures, the averaged behaviors accorded with expectation, often closer examination made possible by single particle tracking revealed novel and unexpected phenomena
Shape and chemically anisotropic colloidal particles: A theoretical study of their structure, phase behavior, and slow dynamics by Mukta Tripathy( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

A detailed non-equilibrium state diagram of shape-anisotropic particle fluids is constructed. The effects of particle shape are explored using Naive Mode Coupling Theory (NMCT), and a single particle Non-linear Langevin Equation (NLE) theory. The dynamical behavior of non-ergodic fluids are discussed. We employ a rotationally frozen approach to NMCT in order to determine a transition to center of mass (translational) localization. Both ideal and kinetic glass transitions are found to be highly shape dependent, and uniformly increase with particle dimensionality. The glass transition volume fraction of quasi 1- and 2- dimensional particles fall monotonically with the number of sites (aspect ratio), while 3-dimensional particles display a non-monotonic dependence of glassy vitrification on the number of sites. Introducing interparticle attractions results in a far more complex state diagram. The ideal non-ergodic boundary shows a glass-fluid-gel re-entrance previously predicted for spherical particle fluids. The non-ergodic region of the state diagram presents qualitatively different dynamics in different regimes. They are qualified by the different behaviors of the NLE dynamic free energy. The caging dominated, repulsive glass regime is characterized by long localization lengths and barrier locations, dictated by repulsive hard core interactions, while the bonding dominated gel region has short localization lengths (commensurate with the attraction range), and barrier locations. There exists a small region of the state diagram which is qualified by both glassy and gel localization lengths in the dynamic free energy. A much larger (high volume fraction, and high attraction strength) region of phase space is characterized by short gel-like localization lengths, and long barrier locations. The region is called the attractive glass and represents a 2-step relaxation process whereby a particle first breaks attractive physical bonds, and then escapes its topological cage. The dynamic fragility of fluids are highly particle shape dependent. It increases with particle dimensionality and falls with aspect ratio for quasi 1- and 2- dimentional particles. An ultralocal limit analysis of the NLE theory predicts universalities in the behavior of relaxation times, and elastic moduli. The equlibrium phase diagram of chemically anisotropic Janus spheres and Janus rods are calculated employing a mean field Random Phase Approximation. The calculations for Janus rods are corroborated by the full liquid state Reference Interaction Site Model theory. The Janus particles consist of attractive and repulsive regions. Both rods and spheres display rich phase behavior. The phase diagrams of these systems display fluid, macrophase separated, attraction driven microphase separated, repulsion driven microphase separated and crystalline regimes. Macrophase separation is predicted in highly attractive low volume fraction systems. Attraction driven microphase separation is charaterized by long length scale divergences, where the ordering length scale determines the microphase ordered structures. The ordering length scale of repulsion driven microphase separation is determined by the repulsive range. At the high volume fractions, particles forgo the enthalpic considerations of attractions and repulsions to satisfy hard core constraints and maximize vibrational entropy. This results in site length scale ordering in rods, and the sphere length scale ordering in Janus spheres, i.e., crystallization. A change in the Janus balance of both rods and spheres results in quantitative changes in spinodal temperatures and the position of phase boundaries. However, a change in the block sequence of Janus rods causes qualitative changes in the type of microphase ordered state, and induces prominent features (such as the Lifshitz point) in the phase diagrams of these systems. A detailed study of the number of nearest neighbors in Janus rod systems reflect a deep connection between this local measure of structure, and the structure factor which represents the most global measure of order
Secondary ion mass spectrometry as a tool to evaluate chemical composition within model and cellular membranes by Christopher R Anderton( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Developing tools to elucidate the chemical distribution of lipid components within the eukaryotic cellular membrane is critical to understanding their role in many cell processes. Secondary ion mass spectrometry (SIMS) is a technique that offers both chemical and spatial specificity, and has become popularized over the last decade for analyzing model and native cellular membranes. Herein, this thesis describes the use and development of SIMS for such samples. By employing high-resolution SIMS, performed on a Cameca NanoSIMS 50, and atomic force microscopy (AFM) the influence of cholesterol on the phase behavior of supported lipid membranes containing saturated phosphatidylcholine lipid species was studied. While the NanoSIMS 50 afforded unprecedented lateral resolution on the chemical distribution of these model membranes, it was achieved at the cost of employing stable-isotope labels for component identification. Time-of-flight SIMS (TOF-SIMS), on the other hand, is a molecular imaging technique that does not require the use of labeled species. However, the ability to image characteristic lipid fragments (i.e. lipid headgroups, etc.) at lateral resolutions comparable to the NanoSIMS 50 is challenging. Furthermore, many of the characteristic fragments are common between structurally similar lipids, such as different phosphatidylcholine species, making discrimination between these species difficult. This challenge was overcome by developing a multivariate analysis (MVA) method, called principal component analysis (PCA), for evaluating the TOF-SIMS spectra of these samples. As a result, the ability to image and identify saturated phosphatidylcholine lipids that differ only in chain length within phase-separated membranes was achieved and could be registered to the corresponding AFM image. By performing PCA to compare TOF-SIMS spectra of labeled and unlabeled species, the molecular ion peaks that are associated with these phosphatidylcholine lipids were identified. These known ion peaks were then used to optimize PCA for TOF-SIMS imaging of phase-separated supported lipid membranes to attain a greater lateral characterization of these samples. The ability to gain quantitative information from TOF-SIMS analysis of homogenous supported lipid membranes was made possible by performing partial least squares regression (PLSR) on the resulting mass spectrum. Here, calibration samples were modeled, and then used to quantitatively predict the content of unknown membrane samples. Lastly, a TOF-SIMS MVA approach was utilized to evaluate native cellular membranes with the goals of differentiating between cell types, and in a separate project, identify the binding of vascular endothelial growth factors to human endothelial cells
Statistical imaging of transport in complex fluids: a journey from entangled polymers to living cells by Bo Wang( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Combining advanced fluorescence imaging, single particle tracking, and quantitative analysis in the framework of statistical mechanics, we studied several transport phenomena in complex fluids with nanometer and millisecond resolution. On the list are diffusion of nanoparticles and vesicles in crowded environments, reptational motion of polymers in entangled semidilute solutions, and active endosome transport along microtubules in living cells. We started from individual trajectories, and then converged statistically to aggregate properties of interests, with special emphasis on the fluctuations buried under the classic mean-field descriptions. The unified scientific theme behind these diversified subjects is to examine, with experiments designed as direct as possible, the commonly believed fundamental assumptions in those fields, such as Gaussian displacements in Fickian diffusion, harmonic confining potential of virtual tubes in polymer entanglements, and bidirectional motion of active intra-cellular transport. This series of efforts led us to discoveries of new phenomena, mechanisms, and concepts. This route, we termed as ⁰́statistical imaging⁰́₊, is expected to be widely useful at studying dynamic processes, especially in those emerging fields at the overlap of physics and biology
Dry sliding wear of metals: From subsurface microstructure to tribological behavior by Wenjun Cai( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Implications of diversity : a study of the evolution of the adsorption states of macromolecules at surfaces by Hildegard Marie Schneider( )

1 edition published in 1995 in English and held by 1 WorldCat member library worldwide

Synthesis and self-assembly of multiblock and Janus particles by Qian Chen( )

1 edition published in 2012 in English and held by 1 WorldCat member library worldwide

Liquid-Cell Electron Microscopy of Adsorbed Polymers( )

1 edition published in 2017 in English and held by 1 WorldCat member library worldwide

Abstract: Individual macromolecules of polystyrene sulfonate and poly(ethylene oxide) are visualized with nanometer resolution using transmission electron microscopy (TEM) imaging of aqueous solutions with and without added salt, trapped in liquid pockets between creased graphene sheets. Successful imaging with 0.3 s per frame is enabled by the sluggish mobility of the adsorbed molecules. This study finds, validating others, that an advantage of this graphene liquid-cell approach is apparently to retard sample degradation from incident electrons, in addition to minimizing background scattering because graphene windows are atomically thin. Its new application here to polymers devoid of metal-ion labeling allows the projected sizes and conformational fluctuations of adsorbed molecules and adsorption-desorption events to be analyzed. Confirming the identification of the observed objects, this study reports statistical analysis of datasets of hundreds of images for times up to 100 s, with variation of the chemical makeup of the polymer, the molecular weight of the polymer, and the salt concentration. This observation of discrete polymer molecules in solution environment may be useful generally, as the findings are obtained using an ordinary TEM microscope, whose kind is available to many researchers routinely. Abstract : Direct real-space investigation of adsorbed polymer dynamics, with single-polymer resolution using conventional transmission electron microscopy (TEM) (transmission liquid microscope) and a graphene liquid cell, gives a time series of polymer images which enables statistical analysis of projected sizes, conformational rearrangements, and adsorption dynamics. This demonstrates the capability of imaging polymers in solution using a conventional TEM
Structure and dynamics of confined chain molecules by John Stephen Peanasky( )

1 edition published in 1995 in English and held by 1 WorldCat member library worldwide

We simultaneously studied the surface forces and dynamics of chain molecules confined between either low energy or high energy surfaces. The surfaces were separated distances on order of the molecular diameter. The surface forces were determined using the Surface Forces Apparatus (SFA) while the dynamics, the relative amounts of elasticity and dissipation, were determined using the surface rheometer. The chain molecules were of alkane, siloxane or perfluorinated polyether chemistry. The alkanes were relatively short and some had methyl side-branches. All were liquids at room temperature. All were dominated by dissipative dynamics in the bulk. The work described focuses on two specific areas: (i) the structure and dynamics of confined long polymeric chains, and (ii) the structure and dynamics of short alkanes. The confining surfaces were either high energy bare mica surfaces or low energy alkane surfaces. The low energy surfaces were necessary in order to distinguish the effects of geometry from surface attraction. To form the low energy surfaces mica had to be modified with self-assembled monolayers of condensed octadecyltriethoxysilane. The modified surfaces were carefully characterized in an effort to prove that the surfaces would meet the strict requirements necessary for SFA experiments. Typically, when surface forces were measurable for confined polymers, so were the dynamics of the thin films. Polymers confined between low energy surfaces could be squeezed more easily to thicknesses smaller than their radius of gyration than if confined between high energy surfaces. Dynamics measurements typically showed elasticity dominating over dissipation. The polymer molecules confined between low energy surfaces were in equilibrium with the chains in the reservoir. Those between high energy surfaces can be in equilibrium with the molecules in the reservoir, provided the rate of surface approach is slow enough for the intrinsic dyanamics of the polymers to dissipate squeezing forces. Shorter alkanes showed layering if they have no methyl side-branches. As the amount of branching increased, the layering was disrupted so that no oscillatory surface forces were measured. On the other hand, molecules with low degree of branching showed a weakly ordered structure, yet layering persisted. Curiously, all of these molecules could show dynamics where the elasticity was larger than dissipation, although both types of forces were measured at levels many orders of magnitude larger than the bulk
Measurements of heat transferred and residence time of a droplet on a hot surface by Ji Yong Park( )

1 edition published in 2013 in English and held by 1 WorldCat member library worldwide

Glassy viscoelasticity of dense suspensions of soft colloids and structure & miscibility of soft filler polymer nanocomposites by Jian Yang( )

1 edition published in 2012 in English and held by 1 WorldCat member library worldwide

Dynamics and assembly of colloidal particles by Jonathan K Whitmer( )

1 edition published in 2012 in English and held by 1 WorldCat member library worldwide

Synthesis of Nanoparticle Assemblies: general discussion( )

1 edition published in 2016 in English and held by 1 WorldCat member library worldwide

Dynamics of Polymer melts confined between absorbing surfaces spaced at molecular dimensions by Hsuan-Wei Hu( )

1 edition published in 1992 in English and held by 1 WorldCat member library worldwide

New physics emerges when polyphenylmethylsiloxane (PPMS) adsorbed between mica surfaces spaced at molecular dimensions undergoes oscillatory shear. The polymers experience a dynamic liquid-like to rubber-like transition at the onset of long range surface forces $(sim$4.5 R$sb{rm G}).$ The long time relaxations of the polymers are effectively frustrated at the start of the strong repulsive short range surface forces (hard-wall $sim$2.8 R$sb{rm G}).$ The static surface forces and dynamic regimes scale with the size of the polymer molecules. This reflects the universal ranges of polymer melts perturbed by the adsorbing surfaces. The dynamics manifest a nonequilibrium freezing of certain degrees of freedom of the molecules as the film thickness decreases. In the rubber-like regime (2.8-4.5 R$sb{rm G}), $ the linear relaxation modulus resembles that of an entangled polymer melt. Surprisingly, the molecular weights of the PPMS are less than the entanglement molecular weight. The dynamics are not reptation in nature; they reflect the long range topological constraints imposed by the adsorbing surfaces. In the short range hard-wall regime $(<$2.8 R$sb{rm G}), $ the impeded long time relaxations indicate the interdigitation of the two polymer layers tethered to the adsorbing surfaces. The structure and correlation in the rubber-like and hard-wall regimes break up when the strain amplitudes are high in the non-linear viscoelastic regime. The short time local relaxations are dominated by the enhanced slip between the segments. The long time global relaxations are accelerated by the strain amplitudes after the rupture of the structure. When viewed at a constant frequency scale, there exist characteristic strains where the dynamic correlation changes. These characteristic strains increase with frequencies; it takes higher strains to break the short time and local correlations
Statistical physics of isotropic-genesis nematic elastomers by Bing Lu( )

1 edition published in 2012 in English and held by 1 WorldCat member library worldwide

 
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Audience level: 0.85 (from 0.76 for Synthesis ... to 0.99 for Stress Rel ...)

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English (23)