Home > Seminars > Fall 2009 Seminar Series
Time: Fridays, 2:00 p.m. - 3:30 p.m.
Location: Aggarwal Lecture Hall, Room 130
Polymer Engineering Academic Center
250 South Forge Street, Akron, OH 44325-0301
Lectures Are Free And Open To The Public
Click here to print the schedule
Date |
Topic / Speaker |
Sept. 4 |
"Batteries, Fuel Cells, and a Start-Up" |
Sept. 11 |
"The Direct Patterning of Organosilicate Materials with Nanoimprint Lithography" |
Sept. 18 |
"Generating Nanostructured Functional Materials Using Block Copolymers" |
Sept. 25 |
"High Performance Architectural Polymers" |
Oct. 9 |
"Electrically Conductive Transparent Polymer Films for Flexible Electronics" |
Oct. 16 |
"Magnetically Actuated Artificial Cilia and Artificial Bacteria Fabricated from the Dipolar Assembly of 23.5 nm Co Nanoparticles" |
Oct. 23 |
"Block Copolymers on Textured Surfaces: Topographically Guided Self-Assembly" |
Oct. 29/30 |
BAYER LECTURESHIP: |
Nov. 6 |
"Chemistry for Surface - A Common Ground of Lithography and Biocompatibility" |
Nov. 20 |
"Gradient Strategies for Biomaterials Optimization and Directing Cell Function" |
Dec. 4 |
"New Polymer Composites and Nanocomposites as Dielectric Capacitor Materials for Pulse
Power Applications" |
"Batteries, Fuel Cells, and a Start-Up"
Dr. Nitash Balsara
Department of Chemical Engineering and
Lawrence Berkeley National Laboratory,
University of California, Berkeley
In work that has the potential to eliminate an important barrier in the manufacturing of high temperature fuel cells, we have created nanostructured block copolymers that, unexpectedly, become wetter as the temperature of the surrounding air gets hotter at constant relative humidity. Thermodynamic laws dictate that all homogeneous hydrophilic materials must become drier as the temperature of the surrounding air increases. The "anti-drying" phenomenon is observed in our materials is thus entirely due to nanostructuring, and it occurs when the width of the hydrated domains in the polymers is less than 6 nm. The presence of water leads to high proton conductivity at temperatures near the boiling point of water. A different class of nanostructured block copolymer electrolytes comprising soft conducting channels embedded in a hard insulating matrix was developed for rechargeable lithium batteries. In contrast to both current liquid and solid electrolytes, the ionic conductivity of the electrolyte increased with increasing molecular weight, thus enabling optimization of both its electrical and mechanical properties. The unusual properties of these electrolytes appear to be related to the distortion of chain configurations in block copolymers. Efforts to create and commercialize all-solid-state rechargeable batteries with significantly better performance than current lithium ion batteries have begun.
"The Direct Patterning of Organosilicate Materials with Nanoimprint Lithography"
Dr. Christpher Soles
Polymers Division,
National Institute of Standards and Technology (NIST)
Organosilicate or silsesquioxane (SSQ) films are widely used in a range applications, including nanocomposites, scratch resistant coatings, barrier coatings, biological devices, porous separation media, optical films or coatings, semiconductor interconnect insulators, and high resolution e-beam resist materials. Some of the key attributes which have lead to this widespread use includes the ease with which they can be processed into high quality films and coatings, the ability of these films and coatings to support high levels of porosity, and their intrinsic resistance to high temperatures and aggressive chemical environments. Recently there has been a growing interest in patterning nanoscale functional devices directly into SSQ materials using nanoimprint lithography (NIL). NIL is a direct patterning process whereby the material being patterned is mechanically squeezed into a rigid mold or template, essentially a nanoscale stamping process. This differs significantly from optical lithography where the pattern is first created in a sacrificial photoresist formulation and then transferred to the functional material of interest via additive and subtractive processes. In this presentation we examine the use of NIL as a high resolution process to directly pattern SSQ materials. The primary target for this work is to simplify fabrication processes and significantly reduce the manufacturing costs for semiconductor interconnect structures. However, the prospect of mechanically forging these materials, especially in their porous form, into nanoscale patterns raises concerns regarding their physical integrity and pore structure. So we have developed critical dimension small angle X-ray scattering and specular X-ray reflectivity methods to verify that an excellent fidelity of the pattern transfer process can be achieved, with minimal pattern shrinkage or distortion [1]. Furthermore, we have also developed the measurement techniques to characterize the porosity characteristics of SSQ patterns, and thus their dielectric constants that are critical to the performance of an interconnect structure. X-ray porosimetry (XRP) is used quantify the average density, the porosity, and the wall density of the material between the pores of these imprinted patterns [2]. All of these parameters characterized by XRP can be resolved as a function of vertical height through the pattern. In addition, positron annihilation lifetime spectroscopy (PALS) measurements are described to quantify the pore size distributions and the degree of pore interconnectivity in the patterned material. Finally, the porosity characteristics determined by XRP and PALS are correlated with high resolution transmission electron microscopy (TEM) images of the pattern cross section to obtain a complete picture of how the imprint process affects the porosity of these materials. Examples will be shown where the porosity level is pushed to over 50 % by volume, well into the ultralow-k regime where the expected dielectric constants will be less than 1.8. In addition to the interconnect applications, we will also show how these SSQ materials can be used to make high resolution daughter NIL molds from an imprint master or template. These daughter molds can be used to then directly imprint a range of materials, including both thermal and UV cross-linkable materials, thereby extending the life of the imprint master.
[1] HW Ro, RL Jones, H Peng, DR Hines, HJ Lee, EK Lin, A Karim, DY Yoon, DW Gidley, CL Soles, Adv. Mater. 19 (2007) 2919.
[2] HW Ro, H Peng, K Nihara, HJ Lee, EK Lin, A Karim, DW Gidley, H Jinnai, DY Yoon , CL Soles, Adv. Mater. 20 (2008) 1934.
"Generating Nanostructured Functional Materials Using Block Copolymers"
Dr. Thomas H. Epps, III
Department of Chemical Engineering
University of Delaware
Soft materials, such as polymers, colloids, surfactants, and liquid crystals, are a technologically important class of matter employed in a variety of applications. One sub-class of soft material, block copolymers, provides the opportunity to design materials with attractive chemical and mechanical properties based on their ability to assemble into periodic structures with nanoscale domain spacings. Several applications for block copolymers currently under investigation in my group include battery and fuel cell membranes, analytical separations membranes, nano-tool templates, precursors to electronic arrays, and drug delivery vehicles. One area of recent progress in the group focuses on the behavior of self-assembled polymer systems doped with various salts. We find that we can tune poly(styrene-b-ethylene oxide) diblock copolymer microstructures by adjusting the lithium counterion as well as the salt concentration. Additionally, we can estimate effective interaction parameters (ceff) for the salt-doped copolymers, which vary predictably with both salt concentration and lithium salt counterion chemistry, and we rationalize our results based on the strength of the chemical interactions between the salt and the polymer backbone. We believe that these systems will enable us to overcome many of the limitations found in current ion-conduction materials, including poor mechanical integrity, poor temperature stability, non-uniform pore sizes, and poor chemical compatibility.
"High Performance Architectural Polymers"
Dr. Babu N. Gaddam
Corporate Research Laboratory,
3M Research Center
The synthesis of oxazolone functional compounds and their use in photochemistry and living radical polymerization will be discussed. The talk will highlight the methods of making polymers with novel architectures and their properties. My research group has also been exploring the synthesis of siloxane polymers. In my talk, I will provide a rationale of designing polymers with specific siloxy units on the polymer chains and their affect on the properties.
"Electrically Conductive Transparent Polymer Films for Flexible Electronics"
Wei Zhao
Doctoral Candidate in Polymer Engineering,
The University of Akron
Transparent conductive films are of great importance in optoelectronic devices. Future wearable/bendable electronics demand not only flexibility, but also stretchability of transparent conductive films incorporated in them as electrodes or sensors. Recently, we developed an electrospinning-solution hybrid process to produce transparent and electrically conductive films. In the process, conductive nanofibers are produced by electrospinning a solution mixture of intrinsically conductive polymer and a carrier polymer. The conductive nanofibers are then embedded partially into the solution cast polymer film. The hybrid films prepared show a surface resistivity as low as 2kOhm/sq with a light transmittance of above 90% within the whole visible range. We demonstrate that the film maintains its conductivity not only during cyclic bending test, but also to a large extent during stretching to high levels of strain in rubbery state stretching. These films are good candidates as flexible transparent conductive electrodes for flexible electronic devices including displays, sensors, photovoltaics.
"Magnetically Actuated Artificial Cilia and Artificial Bacteria Fabricated from the Dipolar Assembly of 23.5 nm Co Nanoparticles"
Dr. Jason J. Benkowski
Milton S. Eisenhower Research Center (MERC),
The Johns Hopkins University Applied Physics Laboratory
Taking inspiration from eukaryotic cilia, we report a method for growing dense arrays of magnetically actuated microscopic filaments. Fabricated from the bottom-up assembly of polymer-coated cobalt nanoparticles, each segmented filament measures approximately 5 - 15 um in length and 23.5 nm in diameter, which was commensurate with the width of a single nanoparticle. A custom microscope stage actuates the filaments through orthogonal permanent and alternating magnetic fields. We implemented design of experiments (DOE) to efficiently screen the effects of cobalt nanoparticle concentration, crosslinker concentration, and surface chemistry. The results indicated that the formation of dense, cilia-mimetic arrays could be explained by physical, non-covalent interactions (i.e. dipolar associations forces) rather than chemistry. We also report the assembly of structures resembling bacteria that are formed from the assembly of the Co nanoparticle filaments with 250 nm magnetite colloids. Also actuated by our custom magnetic stage, the "head" plus "tail" assembly is among the smallest structures capable of swimming.
"Block Copolymers on Textured Surfaces: Topographically Guided Self-Assembly"
Dr. Thomas Russell
Department of Polymer Science
University of Massachusetts, Amherst
By combining confinement effects with the highly directional field inherent in solvent evaporation and the mobility imparted to the BCP by the solvent, perfectly registered arrays of hexagonally packed block copolymer microdomains were produced on surfaces at least 3x3 cm2 in area with areal densities in excess of 10 terabit/inch2. Registry of the arrays and the perfection of the ordering over macroscopic distances were demonstrated by grazing incidence small angle x-ray scattering and scanning force microscopy. This approach circumvents registry constraints and excessive writing times inherent in e-beam lithographic processes over macroscopic length scales and presents a simple route to addressable patterned media.
"Chemistry for Surface - A Common Ground of Lithography and Biocompatibility"
Dr. Li Jia
Department of Polymer Science
The University of Akron
Controlling interactions at materials interface is an overarching topic for scientists and engineers in various disciplines. This presentation describes my group’s efforts to design and chemically modify solid surfaces in order to achieve the desired surface properties for the specific areas of applications. In the case of surface patterning (i.e., lithography), we transfer the pattern initially formed by charged colloidal particles at the air-water interface onto surface-modified solid substrates with the order intact. This is realized by the optimization of attractive forces between the colloids and the solid substrate. To make a surface resistant to protein adsorption (i.e., a biocompatible surface), we have synthesized a group of polymers that, once immobilized on the surface, are expected to optimize the attractive interaction with water and favorably manage the entropic contribution in the process of replacement of water by proteins. The protein adsorption is measured by surface Plasmon resonance spectroscopy (SPR).
"Gradient Strategies for Biomaterials Optimization and Directing Cell Function"
Dr. Matthew Becker
Department of Polymer Science
The University of Akron
Material surface properties influence cell behavior and are a critical parameter in the design of tissue engineered medical products. Surface-mediated interactions dominate the early response of cells to polymeric biomaterials by influencing protein adsorption, cell adhesion and spreading, and extracellular matrix production. Identifying and outlining a framework of how these responses are interrelated for materials optimization is a resource intensive process. Establishing this framework for a class of biomaterials is a measurement intensive regimen that can involve several approaches. This presentation will highlight several examples of recent and ongoing research efforts within my group which demonstrate how precise measurements are able to discriminate between species possessing very small physico-chemical variations and how these incremental differences drastically influence the measured biological outcomes.
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