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Full-Text Articles in Engineering
Solvent Retention In Thin Spin-Coated Polystyrene And Poly(Methyl Methacrylate) Homopolymer Films Studied By Neutron Reflectometry, Alamgir Karim
Solvent Retention In Thin Spin-Coated Polystyrene And Poly(Methyl Methacrylate) Homopolymer Films Studied By Neutron Reflectometry, Alamgir Karim
Alamgir Karim
We utilize neutron reflectometry (NR) to probe the amount of residual solvent in thin polystyrene (PS) and poly(methyl methacrylate) (PMMA) films spin-coated from deuterated toluene solutions onto silicon substrates. The effect of thermal treatment at temperatures below and above the glass transition of PS and PMMA are examined to determine how these treatments affect the residual solvent. The parameters investigated include the total film thickness and molecular mass for PS and only thickness for PMMA. We find that the volume fraction of solvent in PMMA films is less than a few percentages, while no residual solvent was detected in PS …
Versatile Platform For Creating Gradient Combinatorial Libraries Via Modulated Light Exposure, Alamgir Karim
Versatile Platform For Creating Gradient Combinatorial Libraries Via Modulated Light Exposure, Alamgir Karim
Alamgir Karim
This article details the design, construction, and operation of flexible system that modulates light exposure for the purpose of fabricating continuous and discrete gradient combinatorial libraries. Designed for versatility, the device combines "off the shelf" components, modular accessories, and flexible computer control, so that it can be used for a variety of combinatorial research applications. Salient aspects and capabilities of the instrument are illustrated through two practical examples. The first case demonstrates how user defined exposure functions can be used to create continuous surface energy gradient libraries with a linear profile. The second example illustrates the creation of continuous and …
From Finite-Amplitude Equilibrium Structures To Dewetting In Thin Polymer Films On Chemically Patterned Substrates, Amit Sehgal, Dipankar Bandyopadhyay, Kajari Kargupta, Ashutosh Sharma, Alamgir Karim
From Finite-Amplitude Equilibrium Structures To Dewetting In Thin Polymer Films On Chemically Patterned Substrates, Amit Sehgal, Dipankar Bandyopadhyay, Kajari Kargupta, Ashutosh Sharma, Alamgir Karim
Alamgir Karim
We study templating and patterning strategies of an ultrathin (<100 >nm) polystyrene (PS) film on substrates with varying lateral confinement produced by linear chemical patterns. The patterned surfaces are fabricated by coating self-assembled monolayers (SAMs) of alternating less (–CH3) and more wettable (–COOH) micro-stripes on gold-coated silicon surfaces. The width of the less wettable stripe was changed from 1 to 15 μm to uncover the influence of the lateral confinement on the dewetted patterns while keeping constant the film thickness (65 nm) and the width of the more wettable stripes (3 μm). When the less wettable stripes are highly confined …
Fullerene Nanoparticles As Molecular Surfactant For Dewetting Of Phase-Separating Polymer Blend Films, Diya Bandyopadhyay, Jack Douglas, Alamgir Karim
Fullerene Nanoparticles As Molecular Surfactant For Dewetting Of Phase-Separating Polymer Blend Films, Diya Bandyopadhyay, Jack Douglas, Alamgir Karim
Alamgir Karim
We investigate the effects of fullerene nanoparticles (f-NP) on the dewetting morphology in the immiscible temperature regime of blend films of polystyrene (PS) and polybutadiene (PB) on silicon substrate. As in our former work in the miscible temperature regime of this blend film, competitive partitioning of the f-NPs to the polymer–polymer and the substrate interfaces in blend films requires a larger concentration of f-NPs (10 mass %) to suppress film dewetting than in homopolymer components (2 mass %). In contrast, however, phase-separated blend films rapidly dewet into hemispherical droplets due to finite interfacial tension of internal blend components unlike irregular …
Diblock Copolymer Lamellae On Sinusoidal And Fractal Surfaces, Alamgir Karim, Amit Ranjan, Manish Kulkarni, Ashutosh Sharma
Diblock Copolymer Lamellae On Sinusoidal And Fractal Surfaces, Alamgir Karim, Amit Ranjan, Manish Kulkarni, Ashutosh Sharma
Alamgir Karim
A scaling analysis of equilibrium orientation of diblock copolymer molecules on fractal surfaces and a brief comparison with a particular experiment is presented in this paper. This work is motivated by a recent experimental finding that a diblock copolymer film of polystyrene-PMMA, when deposited on a rough substrate, can orient its lamellae from a parallel to a perpendicular configuration depending on the topographical characteristics of the substrate surface. It was found that the RMS height itself is not enough to effect the equilibrium configuration, but the fractal dimension of the surface is also important. In general, the orientation of lamellae …
Dynamic Thermal Field Induced Gradient Soft-Shear For Highly Oriented Block Copolymer Thin Films, Gurpreet Singh, Kevin Yager, Brian Berry, Ho-Cheol Kim, Alamgir Karim
Dynamic Thermal Field Induced Gradient Soft-Shear For Highly Oriented Block Copolymer Thin Films, Gurpreet Singh, Kevin Yager, Brian Berry, Ho-Cheol Kim, Alamgir Karim
Alamgir Karim
As demand for smaller, more powerful, and energy-efficient devices continues, conventional patterning technologies are pushing up against fundamental limits. Block copolymers (BCPs) are considered prime candidates for a potential solution via directed self-assembly of nanostructures. We introduce here a facile directed self-assembly method to rapidly fabricate unidirectionally aligned BCP nanopatterns at large scale, on rigid or flexible template-free substrates via a thermally induced dynamic gradient soft-shear field. A localized differential thermal expansion at the interface between a BCP film and a confining polydimethylsiloxane (PDMS) layer due to a dynamic thermal field imposes the gradient soft-shear field. PDMS undergoes directional expansion …
Photocurable Oil/Water Interfaces As A Universal Platform For 2-D Self-Assembly, Alamgir Karim
Photocurable Oil/Water Interfaces As A Universal Platform For 2-D Self-Assembly, Alamgir Karim
Alamgir Karim
We present a novel platform, dubbed fossilized liquid assembly, for the creation of 2-D assemblies from nanoscale building blocks. The system consists of an oil/water interface in which the oil phase can be flash-cured upon UV exposure. The photopolymerizable material, 1,12-dodecanediol dimethacrylate, solidifies in as little as 1 s when exposed to UV light. The rapid cross-linking allows one to obtain a "snapshot" of the assembly process for particles that segregate to the oil/water interface. Among the particles investigated were nonpolar 0.39 microm poly(methyl methacrylate) latex spheres, nonpolar 10 microm polystyrene latex spheres, highly polarizable 5 nm Au nanocrystals, dipolar …
Dielectric Spectroscopy Investigation Of Relaxation In C-60-Polyisoprene Nanocomposites, Alamgir Karim
Dielectric Spectroscopy Investigation Of Relaxation In C-60-Polyisoprene Nanocomposites, Alamgir Karim
Alamgir Karim
We investigate the influence of adding C60 nanoparticles on the dielectric relaxation spectra of both unentangled and entangled polyisoprene (PIP). Relaxation modes corresponding to both the segmental and chain relaxation were analyzed over a broad temperature and frequency range. Regardless of whether the chains were entangled or not, both relaxation processes slowed down with the addition of C60, reflecting an increase of the nanocomposite glass transition temperature. However, C60 affects the segmental relaxation more strongly than the large-scale chain relaxation, both in terms of the relaxation time and strength, suggesting that the effect of the nanoparticles on the polymer dynamics …
Tuning Molecular Relaxation For Vertical Orientation In Cylindrical Block Copolymer Films Via Sharp Dynamic Zone Annealing, Gurpreet Singh, Kevin Yager, Detlef-M. Smilgies, Manish Kulkarni, David Bucknall, Alamgir Karim
Tuning Molecular Relaxation For Vertical Orientation In Cylindrical Block Copolymer Films Via Sharp Dynamic Zone Annealing, Gurpreet Singh, Kevin Yager, Detlef-M. Smilgies, Manish Kulkarni, David Bucknall, Alamgir Karim
Alamgir Karim
Fabricating vertically ordered and etchable high aspect ratio nanodomains of block copolymer (BCP) thin films on diverse substrates via continuous processing dynamic cold zone annealing (CZA) is particularly attractive for nanomanufacturing of next-generation electronics. Previously, we reported dynamic CZA studies with a shallow thermal gradient (maximum del T similar to 14 degrees C/mm) that produced only BCP cylinders oriented parallel to substrate. Here, we report a CZA utilizing a dynamic sharp thermal gradient (del T similar to 45 degrees C/mm) (i.e., CZA-S). This method allows for production of etchable and vertically oriented cylindrical domains of poly(styrene-b-methyl methacrylate) in 100-1000 rim …
Quantification Of The Binding Affinity Of A Specific Hydroxyapatite Binding Peptide, Michael Weiger, Jung Park, Marc Roy, Christopher Stafford, Alamgir Karim, Matthew Becker
Quantification Of The Binding Affinity Of A Specific Hydroxyapatite Binding Peptide, Michael Weiger, Jung Park, Marc Roy, Christopher Stafford, Alamgir Karim, Matthew Becker
Alamgir Karim
The genesis of bone and teeth involves highly coordinated processes, which involve multiple cell types and proteins that direct the nucleation and crystallization of inorganic hydroxyapatite (HA). Recent studies have shown that peptides mediate the nucleation process, control HA microstructure or even inhibit HA mineralization. Using phage display technology, a short peptide was identified that binds to crystalline HA and to HA-containing domains of human teeth with chemical and morphological specificity. However, the binding affinity and specific amino acids that significantly contribute to this interaction require further investigation. In this study, we employ a microfluidic chip based surface plasmon resonance …
Influence Of C60 Nanoparticles On The Stability And Morphology Of Miscible Polymer Blend Films, Diya Bandyopadhyay, Jack Douglas, Alamgir Karim
Influence Of C60 Nanoparticles On The Stability And Morphology Of Miscible Polymer Blend Films, Diya Bandyopadhyay, Jack Douglas, Alamgir Karim
Alamgir Karim
We investigate the influence of fullerene (C60) nanoparticle (NP) additives on a thermodynamically miscible polymer blend thin film of polystyrene (PS) and polybutadiene (PB). In this system both homopolymer components individually dewet from the commonly used silicon substrate. Three NP concentration regimes having distinct blend nanocomposite film morphologies are observed: (a) In the neat blend and low NP mass (0–1%) range, the blend films rapidly dewet, apparently due to fluctuations in the polymer surface tension arising from the composition fluctuations of a surface enrichment layer at the film air boundary. This behavior is in sharp contrast to the corresponding NP-filled …
Using Block Copolymer Self-Assembly To Imprint The Crystallization Of Polymer Dendrites, Sangcheol Kim, Jack Douglas, Christopher Soles, Alamgir Karim, R. Briber
Using Block Copolymer Self-Assembly To Imprint The Crystallization Of Polymer Dendrites, Sangcheol Kim, Jack Douglas, Christopher Soles, Alamgir Karim, R. Briber
Alamgir Karim
We utilize the self-assembly of cylinder-forming block copolymer (BCP) films to create templates for dendritic polymercrystallization patterns. This templating was achieved by simply spin-casting thin films from a solution containing both the BCP [polystyrene-block-poly(ethylene oxide) (PS-b-PEO)] and a homopolymer (polyethylene oxide) under controlled vapor atmosphere conditions, without the need for any additional processing (e.g. solvent or thermal annealing). The BCP first organized into a hexagonal array of vertically oriented PEO cylinders that served to template dendritic PEOhomopolymer crystals on the surface of the BCP pattern. No surface defects such as dewetting holes or macroscopically phase-separated domains were observed on top …
Uvo-Tunable Superhydrophobic To Superhydrophilic Wetting Transition On Biomimetic Nanostructured Surfaces, Alamgir Karim
Uvo-Tunable Superhydrophobic To Superhydrophilic Wetting Transition On Biomimetic Nanostructured Surfaces, Alamgir Karim
Alamgir Karim
A novel strategy for a tunable sigmoidal wetting transition from superhydrophobicity to superhydrophilicity on a continuous nanostructured hybrid film via gradient UV-ozone (UVO) exposure is presented. Along a single wetting gradient surface (40 mm), we could visualize the superhydrophobic (thetaH2O > 165 degrees and low contact angle hysteresis) transition (165 degrees > thetaH2O > 10 degrees ) and superhydrophilic (thetaH2O < 10 degrees within 1 s) regions simply through the optical images of water droplets on the surface. The film is prepared through layer-by-layer assembly of negatively charged silica nanoparticles (11 nm) and positively charged poly(allylamine hydrochloride) with an initial deposition in a fractal …
Direct Observation Of Interfacial C-60 Cluster Formation In Polystyrene-C-60 Nanocomposite Films, Alamgir Karim
Direct Observation Of Interfacial C-60 Cluster Formation In Polystyrene-C-60 Nanocomposite Films, Alamgir Karim
Alamgir Karim
Large interfacial C(60) clusters were directly imaged at the supporting film-substrate interface in physically detached polystyrene-C(60) nanocomposite films by atomic force microscopy, confirming the stabilizing mechanism previously hypothesized for thin polymer films. Additionally, we found that the C(60) additive influences basic thermodynamic film properties such as the interfacial energy and the film thermal expansion coefficient.
Directed Assembly Of Block Copolymer Films: Effects Of Rough Substrates And Thermal Fields, Manish Kulkarni, Alamgir Karim, Kevin Yager
Directed Assembly Of Block Copolymer Films: Effects Of Rough Substrates And Thermal Fields, Manish Kulkarni, Alamgir Karim, Kevin Yager
Alamgir Karim
Polymer coatings are used extensively as passive masking layers or active materials in diverse fields such as consumer products, microelectronics, and biomedical implants. A high packing density of functional elements is required for a wide variety of next-generation technologies, including high resolution displays, fast microprocessors, and lightweight batteries with high power densities. Photolithographic patterning of photosensitive polymers (i.e., photoresists) is currently the most popular industrial option to create such small scale structures. This technology has been so far successful in increasing the packing density of functional elements and decreasing pattern sizes to about 64 nm by the use of smaller …
The Direct Patterning Of Nanoporous Interlayer Dielectric Insulator Films By Nanoimprint Lithography, Alamgir Karim
The Direct Patterning Of Nanoporous Interlayer Dielectric Insulator Films By Nanoimprint Lithography, Alamgir Karim
Alamgir Karim
No abstract provided.