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1,397 full-text articles. Page 48 of 48.

Hierarchically Ordered Montmorillonite Block Copolymer Brushes, Ross Eric Behling, Lynn M. Wolf, Eric W. Cochran 2010 Iowa State University

Hierarchically Ordered Montmorillonite Block Copolymer Brushes, Ross Eric Behling, Lynn M. Wolf, Eric W. Cochran

Chemical and Biological Engineering Publications

Block copolymers (BCPs) have been known for decades to offer an easily tunable method for producing self-assembled structures with length scales on the order of nanometers. More recently, the community has shown significant interest in exploiting the properties of BCP self-assembly to tailor the spatial and orientational distribution of nanoscale filler materials, with targeted applications ranging from high-density storage devices, to organic electronics, to optical devices, and to separation devices/catalytic membranes.


Symmetry Transition In Thin Films Of Diblock Copolymer/Homopolymer Blends, Vindhya Mishra, Su-Mi Hur, Eric W. Cochran, Gila E. Stein, Glenn H. Fredrickson, Edward J. Kramer 2010 University of California, Santa Barbara

Symmetry Transition In Thin Films Of Diblock Copolymer/Homopolymer Blends, Vindhya Mishra, Su-Mi Hur, Eric W. Cochran, Gila E. Stein, Glenn H. Fredrickson, Edward J. Kramer

Chemical and Biological Engineering Publications

The effect of blending small weight fractions of low molecular weight majority block homopolymer on the structure of multilayer films of spherical morphology poly(styrene-b-2vinylpyridine) [PS−P2VP] has been studied. The structure of the films was characterized with grazing-incidence small-angle X-ray scattering (GISAXS) and transmission electron microscopy (TEM). In multilayer films of PS−P2VP, competition between hexagonal packing of the spherical domains preferred at the surfaces with the BCC (110) packing preferred by the internal layers leads to a transition in the packing symmetry as the number of sphere layers (n) is increased.(1) Neat PS−P2VP exhibits ...


Selective Recursive Kernel Learning For Online Identification Of Nonlinear Systems With Narx Form, Yi Liu, Haiqing Wang, Jiang Yu, Ping Li 2010 Zhejiang University

Selective Recursive Kernel Learning For Online Identification Of Nonlinear Systems With Narx Form, Yi Liu, Haiqing Wang, Jiang Yu, Ping Li

Dr. Yi Liu

Online identification of nonlinear systems is still an important while difficult task in practice. A general and simple online identification method, namely Selective Recursive Kernel Learning (SRKL), is proposed for multi-input–multi-output (MIMO) systems with the nonlinear autoregressive with exogenous input form. A two-stage RKL online identification framework is first formulated, where the information contained by a sample (i.e., the new arriving or old useless one) can be introduced into and/or deleted from the model, recursively. Then, a sparsification strategy to restrict the model complexity is developed to guarantee all the output channels of the MIMO model accurate ...


Polymer Composites And Porous Materials Prepared By Thermally Induced Phase Separation And Polymer-Metal Hybrid Methods, Joonsung Yoon 2010 University of Massachusetts Amherst

Polymer Composites And Porous Materials Prepared By Thermally Induced Phase Separation And Polymer-Metal Hybrid Methods, Joonsung Yoon

Open Access Dissertations

The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the ...


Analysis Of Non-Covalent Interactions Between The Nanoparticulate Fillers And The Matrix Polymer As Applied To Shape Memory Performance, I. Sedat Gunes, Cesar Perez-Bolivar, Feina Cao, Guillermo A. Jimenez, Pavel Anzenbacher, Sadhan C. Jana 2010 University of Akron Main Campus

Analysis Of Non-Covalent Interactions Between The Nanoparticulate Fillers And The Matrix Polymer As Applied To Shape Memory Performance, I. Sedat Gunes, Cesar Perez-Bolivar, Feina Cao, Guillermo A. Jimenez, Pavel Anzenbacher, Sadhan C. Jana

Sadhan C Jana

Non-covalent interactions between filler particles and polyurethanes were investigated using fluorescence emission spectroscopy. The results were used in the analysis of shape memory (SM) performance of polyurethanes. Composites of shape memory polyurethane (SMPU) and carbon nanofiber (CNF), oxidized carbon nanofiber (ox-CNF), organoclay, silicon carbide, and carbon black were prepared from diphenylmethane diisocyanate, 1,4-butanediol, and poly(caprolactone) diol. It was revealed by fluorescence emission spectroscopy that primarily the urethane groups located in the hard segments of SMPU interacted with the polar functional groups on filler particles. A close correlation between the extent of non-covalent filler-matrix interactions, soft segment crystallinity, and ...


Effect Of Mesoporosity On Thermal And Mechanical Properties Of Polystyrene/Silica Composites, Melissa A. Ver Meer, Balaji Narasimhan, Brent H. Shanks, Surya K. Mallapragada 2010 Schlumberger Lawrence Technology Center

Effect Of Mesoporosity On Thermal And Mechanical Properties Of Polystyrene/Silica Composites, Melissa A. Ver Meer, Balaji Narasimhan, Brent H. Shanks, Surya K. Mallapragada

Chemical and Biological Engineering Publications

In this study, mesoporous or colloidal silica particles were incorporated into polystyrene matrices via melt blending or by styrene polymerization initiated from the particle surface. The relationships between the surface morphology of filler particles in polymer composites and their thermomechanical properties were investigated. High molecular weight polystyrene-silica hybrids were generated by modifying the surfaces of monodisperse colloidal silica and templated mesoporous silica nanoparticles. The functionalized silica surfaces were grafted with alkyl halide initiators for atom transfer radical polymerization. Polymerization was conducted without free initiator present. The physical properties of these composites were studied by dynamic mechanical analysis, thermogravimetric analysis, transmission ...


Novel, High Throughput Method To Study In Vitro Protein Release From Polymer Nanospheres, L. K. Petersen, C. K. Sackett, Balaji Narasimhan 2010 Iowa State University

Novel, High Throughput Method To Study In Vitro Protein Release From Polymer Nanospheres, L. K. Petersen, C. K. Sackett, Balaji Narasimhan

Chemical and Biological Engineering Publications

Controlled delivery of therapeutic protein drugs using biodegradable polymer carriers is a desired characteristic that enables effective, application-specific therapy and treatment. Previous studies have focused on protein delivery from polymers using conventional "one-sample-at-a- time" techniques, which are time-consuming and costly. In addition, many therapeutic proteins are in limited supply and are expensive, so it is desirable to reduce sample size for design and development of delivery devices. We have developed a rapid, high throughput technique based on a highly sensitive fluorescence-based assay to detect and quantify protein released from polyanhydrides while utilizing relatively small amounts of protein (∼40 μg). These ...


Book Review: Controlled And Living Polymerizations: From Mechanisms To Applications, Jennifer M. Heinen 2010 Iowa State University

Book Review: Controlled And Living Polymerizations: From Mechanisms To Applications, Jennifer M. Heinen

Chemical and Biological Engineering Publications

Controlled/living polymerization makes it possible to synthesize polymers of low polydispersity with a predefined molecular weight and specified chain architecture. Such polymers are desirable for a broad range of applications, including coatings, adhesives, and lubricants. Although living polymerization was first discovered in anionic polymerizations in 1956, several decades passed prior to the development of living polymerization techniques for carbocationic polymerization (1984) and ring-opening metathesis polymerization (1986). During the 1990s, several techniques were developed for controlled/living free radical polymerizations. The development of these techniques led to a dramatic increase in the number of research publications dedicated to improving the ...


Molecular Dynamics Simulation Of Poly(Ethylene Terephthalate) Oligomers, David Keffer, Qifei Wang, Simioan Petrovan, J. Thomas 2009 University of Tennessee - Knoxville

Molecular Dynamics Simulation Of Poly(Ethylene Terephthalate) Oligomers, David Keffer, Qifei Wang, Simioan Petrovan, J. Thomas

David Keffer

Molecular dynamics simulations of poly(ethylene terephthalate) (PET) oligomers are performed in the isobaric−isothermal (NpT) ensemble at a state point typical of a finishing reactor. The oligomer size ranges from 1 to 10 repeat units. We report thermodynamic properties (density, potential energy, enthalpy, heat capacity, isothermal compressibility, and thermal expansivity), transport properties (self-diffusivity, zero-shear-rate viscosity, thermal conductivity), and structural properties (pair correlation functions, hydrogen bonding network, chain radius of gyration, chain end-to-end distance) as a function of oligomer size. We compare the results with existing molecular-level theories and experimental data. Scaling exponents as a function of degree of polymerization ...


Molecular Simulations Of H2 Adsorption In Metal-Porphyrin Frameworks (Mpfs): A Potential New Material Evaluation, Ruichang Xiong, David Keffer 2009 University of Tennessee - Knoxville

Molecular Simulations Of H2 Adsorption In Metal-Porphyrin Frameworks (Mpfs): A Potential New Material Evaluation, Ruichang Xiong, David Keffer

David Keffer

Path integral grand canonical Monte Carlo (PI-GCMC) simulations using standard force fields are carried out to calculate the adsorption of H2 in five metal-porphyrin frameworks (MPFs), a new class of metal organic framework (MOF)-type materials. These simulations are performed at 77 K and room temperature (300 K). The adsorption isotherms of H2 in IRMOF-1 and IRMOF-10 are also calculated as a comparison. All calculations indicate that all MPFs adsorbed a higher weight fraction of H2 than both IRMOF-1 and IRMOF-10, with one exception (MPF-2). The gravimetric hydrogen capacities are still well short of practical goals. The MPFs provide additional ...


Molecular Simulation Images, David Keffer 2009 University of Tennessee - Knoxville

Molecular Simulation Images, David Keffer

David Keffer

These animations and interactive structures are created from various molecular dynamics simulations and quantum calculations. In order to view the interactive structures, you need the free "Chime" Plug-in. In order to view the movie files (in avi format), you will require the following codec: TSCC codec. This work has been supported by DOE BES, AFOSR, NSF and ACS PRF.


Effective Potentials Between Nanoparticles In Suspension, Gary Grest, Qifei Wang, Pieter in't Veld, David Keffer 2009 University of Tennessee - Knoxville

Effective Potentials Between Nanoparticles In Suspension, Gary Grest, Qifei Wang, Pieter In't Veld, David Keffer

David Keffer

Results of molecular dynamics simulations are presented for the pair distribution function between nanoparticles in an explicit solvent as a function of nanoparticle diameter and interaction strength between the nanoparticle and solvent. The effect of including the solvent explicitly is demonstrated by comparing the pair distribution function of nanoparticles to that in an implicit solvent. The nanoparticles are modeled as a uniform distribution of Lennard-Jones particles, while the solvent is represented by standard Lennard-Jones particles. The diameter of the nanoparticle is varied from 10 to 25 times that of the solvent for a range of nanoparticle volume fractions. As the ...


Dynamics Of Individual Molecules Of Linear Polyethylene Liquids Under Shear: Atomistic Simulation And Comparison With A Free-Draining Bead-Rod Chain, David Keffer, J. Kim, B. Edwards, B. Khomami 2009 University of Tennessee - Knoxville

Dynamics Of Individual Molecules Of Linear Polyethylene Liquids Under Shear: Atomistic Simulation And Comparison With A Free-Draining Bead-Rod Chain, David Keffer, J. Kim, B. Edwards, B. Khomami

David Keffer

Nonequilibrium molecular dynamics (NEMD) simulations of a dense liquid composed of linear polyethylene chains were performed to investigate the chain dynamics under shear. Brownian dynamics (BD) simulations of a freely jointed chain with equivalent contour length were also performed in the case of a dilute solution. This allowed for a close comparison of the chain dynamics of similar molecules for two very different types of liquids. Both simulations exhibited a distribution of the end-to-end vector, |Rete|, with Gaussian behavior at low Weissenberg number (Wi). At high Wi, the NEMD distribution was bimodal, with two peaks associated with rotation and ...


Poly(Beta-Alanoid-Block-Beta-Alanine)S: Synthesis Via Cobalt-Catalyzed Carbonylative Polymerization And Self-Assembly, Shaohui Lin, Xinfei Yu, Yinfeng Tu, Hongyu Xu, Stephen Cheng, Li Jia 2009 University of Akron Main Campus

Poly(Beta-Alanoid-Block-Beta-Alanine)S: Synthesis Via Cobalt-Catalyzed Carbonylative Polymerization And Self-Assembly, Shaohui Lin, Xinfei Yu, Yinfeng Tu, Hongyu Xu, Stephen Cheng, Li Jia

Stephen Z. D. Cheng

The titled diblock copolymers are synthesized via cobalt-catalyzed living carbonylative polymerization of N-alkylaziridines under moderate pressures followed by a deprotection step. The poly(beta-alanine) block is solubilized by the poly(beta-alanoid) block in chloroform and remains fully hydrogen-bonded in the form of a sheet-like assembly.


Apolar Ortho-Phenylene Ethynylene Oligomers: Conformational Ordering Without Intermolecular Aggregation, Jing Jiang, Morris M. Slutsky, Ticora V. Jones, Gregory N. Tew 2009 University of Massachusetts - Amherst

Apolar Ortho-Phenylene Ethynylene Oligomers: Conformational Ordering Without Intermolecular Aggregation, Jing Jiang, Morris M. Slutsky, Ticora V. Jones, Gregory N. Tew

Gregory N. Tew

This paper describes the characterization of solvent induced folding behavior for non-polar (NP) alkoxy substituted ortho-phenylene ethynylene (o-PE) oligomers. Oligomers of lengths up to nine units have been shown to adopt helical conformations in heptane by NMR and CD spectroscopy, while chloroform promotes extended conformations. Surprisingly, the molar ellipticity values found in heptane for these oligomers are very small compared to other literature values of meta-phenylene ethynylene (m-PE) folded systems; however, comparable molar ellipticity values were found for a closed macrocyclic o-PE suggesting the weak ellipticity is a molecular-feature rather than a quality of folding indicator.


Evolution Of Block-Copolymer Order Through A Moving Thermal Zone, Kevin G. Yager, Nathaniel J. Fredin, Xiaohua Zhang, Brian C. Berry, Alamgir Karim, Ronald L. Jones 2009 University of Akron

Evolution Of Block-Copolymer Order Through A Moving Thermal Zone, Kevin G. Yager, Nathaniel J. Fredin, Xiaohua Zhang, Brian C. Berry, Alamgir Karim, Ronald L. Jones

Alamgir Karim

We investigate block-copolymer (BCP) thin film ordering kinetics during annealing across a moving in-plane temperature gradient. We operate in the so-called cold zone annealing (CZA) regime, where ordering temperatures are above the glass-transition, but well below the order-disorder transition. By measuring the order through the in-plane gradient, using atomic force microscopy and grazing-incidence small-angle X-ray scattering (GISAXS), we confirm that CZA greatly enhances ordering kinetics, as compared to uniform oven annealing. The maximal ordering occurs over a narrow range of the heating-up phase, and not during the subsequent cooling phase. The large grain sizes obtained using CZA are due to ...


Observation Of A Characteristic Length Scale In The Healing Of Glassy Polymer Interfaces, Guangcui Yuan, Clive Li, Sushil K. Satija, Alamgir Karim, Jack F. Douglas, Charles C. Han 2009 University of Akron

Observation Of A Characteristic Length Scale In The Healing Of Glassy Polymer Interfaces, Guangcui Yuan, Clive Li, Sushil K. Satija, Alamgir Karim, Jack F. Douglas, Charles C. Han

Alamgir Karim

We examine the evolution (‘healing’) of the interface between two polymer films at various temperatures below the glass transition temperature, Tg. Specifically, neutron reflectometry is used to study the relaxation of the interface between both unentangled and entangled deuterated polystyrene (d-PS) and hydrogenated polystyrene (h-PS) films in the glass state where these bilayer films are supported on silicon substrates. We find that the initially sharp interface between the glassy polymer layers broadens with time (t), but the average interfacial thickness Δσ(t) between these layers then saturates after long time to a thickness (ξp) in a range between 1 nm ...


Spr Imaging Study Of Dna Wrapped Single Wall Carbon Nanotube (Ssdna-Swcnt) Adsorption On A Model Biological (Collagen) Substrate, Jung Jin Park, Jeffrey A. Fagan, Ji Yeon Huh, Kalman B. Migler, Alamgit Karim, Dharmaraj Raghaven 2009 University of Akron

Spr Imaging Study Of Dna Wrapped Single Wall Carbon Nanotube (Ssdna-Swcnt) Adsorption On A Model Biological (Collagen) Substrate, Jung Jin Park, Jeffrey A. Fagan, Ji Yeon Huh, Kalman B. Migler, Alamgit Karim, Dharmaraj Raghaven

Alamgir Karim

The adsorption kinetics of single stranded-DNA dispersed single wall carbon nanotubes (ssDNA-SWCNTs) onto an immobilized collagen layer in a microfluidic channel was probed using surface plasmon resonance imaging (SPRi). The adsorption was measured for a range of both nanotube and solution parameters including the nanotube concentration, nanotube length, solution pH, and the type of medium (buffer and river water). The kinetic adsorption data suggests that the adsorption of the nanotubes to the collagen layer is irreversible in HEPES buffer, pH ≈ 7.4, at room temperature, with the nanotube adsorption displaying two different kinetic adsorption regimes for different concentration ranges. A ...


Poly(Beta-Alanoid-Block-Beta-Alanine)S: Synthesis Via Cobalt-Catalyzed Carbonylative Polymerization And Self-Assembly, Shaohui Lin, Xinfei Yu, Yinfeng Tu, Hongyu Xu, Stephen Z. D. Cheng, Li Jia 2009 University of Akron Main Campus

Poly(Beta-Alanoid-Block-Beta-Alanine)S: Synthesis Via Cobalt-Catalyzed Carbonylative Polymerization And Self-Assembly, Shaohui Lin, Xinfei Yu, Yinfeng Tu, Hongyu Xu, Stephen Z. D. Cheng, Li Jia

Li Jia

The titled diblock copolymers are synthesized via cobalt-catalyzed living carbonylative polymerization of N-alkylaziridines under moderate pressures followed by a deprotection step. The poly(beta-alanine) block is solubilized by the poly(beta-alanoid) block in chloroform and remains fully hydrogen-bonded in the form of a sheet-like assembly.


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