Conferences, Lectures, & Seminars
Events for December
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Novel Liquid Crystal Networks
Mon, Dec 01, 2008 @ 01:00 PM
Mork Family Department of Chemical Engineering and Materials Science
Conferences, Lectures, & Seminars
Mork Family Department of Cheical Engineering & Material Science Presents:Rafael Verduzco
Oak Ridge National Laboratory Oak Ridge, TN"Novel Liquid Crystal Networks"AbstractThe combination of liquid crystals and polymers results in fascinating materials in which the elasticity of polymers is coupled to the liquid crystal (LC) order. In this work, we present three qualitatively different types of LC gels and elastomers and explore their electro-optical response, mechanical actuation, and flexoelectric behavior. Using block copolymer self-assembly, we prepare LC physical gels that exhibit fascinating texture transitions with temperature and multiple director relaxation modes, in contrast to covalent gels which show a single relaxation mode. Next, covalent networks with a controlled molecular weight between cross-links were prepared by "click" cross-linking of telechelic polymers produced by ring-opening metathesis polymerization. These networks swell readily in a small molecular LC solvent, 5CB, to form LC gels with high swelling ratios that exhibit a fast, reversible, and low-threshold electro-optic response. Finally, a series of bent-core liquid crystals were synthesized and used to swell calamitic monodomain liquid crystal elastomers (LCE). Nematic bent-core liquid crystals show enhanced flexoelectricity, and bent-core elastomers represent a potential method for incorporating flexoelectricity into a robust polymeric device. These LC networks and gels provide insight into the connection between physical properties and network structure and also demonstrate the broad range of materials accessible with different synthetic approaches.
Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116
Audiences: Everyone Is Invited
Contact: Petra Pearce Sapir
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Novel Liquid Crystal Networks
Mon, Dec 08, 2008 @ 01:00 PM
Mork Family Department of Chemical Engineering and Materials Science
Conferences, Lectures, & Seminars
Mork Family Department of Chemical Engineering and Material Science Presents:"Novel Liquid Crystal Networks"Rafael Verduzco
Oak Ridge National Laboratory
Oak Ridge, TNAbstractThe combination of liquid crystals and polymers results in fascinating materials in which the elasticity of polymers is coupled to the liquid crystal (LC) order. In this work, we present three qualitatively different types of LC gels and elastomers and explore their electro-optical response, mechanical actuation, and flexoelectric behavior. Using block copolymer self-assembly, we prepare LC physical gels that exhibit fascinating texture transitions with temperature and multiple director relaxation modes, in contrast to covalent gels which show a single relaxation mode. Next, covalent networks with a controlled molecular weight between cross-links were prepared by "click" cross-linking of telechelic polymers produced by ring-opening metathesis polymerization. These networks swell readily in a small molecular LC solvent, 5CB, to form LC gels with high swelling ratios that exhibit a fast, reversible, and low-threshold electro-optic response. Finally, a series of bent-core liquid crystals were synthesized and used to swell calamitic monodomain liquid crystal elastomers (LCE). Nematic bent-core liquid crystals show enhanced flexoelectricity, and bent-core elastomers represent a potential method for incorporating flexoelectricity into a robust polymeric device. These LC networks and gels provide insight into the connection between physical properties and network structure and also demonstrate the broad range of materials accessible with different synthetic approaches.
Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116
Audiences: Everyone Is Invited
Contact: Petra Pearce Sapir
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Annual Pings Lecture: Confronting the Climate-Energy Challenge
Tue, Dec 09, 2008 @ 03:00 PM
Mork Family Department of Chemical Engineering and Materials Science
Conferences, Lectures, & Seminars
Mork Family Department of Chemical Engineering & Material Science Annual Ping's LecturePresentsProfessor Daniel Schrag
Harvard University, Department of Earth and Planetary Sciences and
School of Engineering and Applied SciencesConfronting the Climate-Energy ChallengeAbstractThe increase in atmospheric CO2 due to burning coal, oil and gas represents an unprecedented experiment on the Planet Earth. We know from air bubbles trapped in ice cores that CO2 has never been higher than 300 parts per million in the last 650,000 years, and from indirect measurements, we think it was not significantly higher than this for tens of millions of years. Geologic records of climate change, as well as observations of neighboring planets, provide a variety of important lessons that can guide us in evaluating the risks of future climate change. In general, the uncertainties in our understanding of the climate system are biased towards lack of knowledge about catastrophic events. In this context, a variety of strategies will be discussed for meeting the world's energy needs with the smallest possible impact on our atmosphere, as well as considering what strategies we might require if climate change is more dramatic than we expect.Daniel Schrag is the Director of the Harvard University Center for the Environment and Professor of Earth and Planetary Sciences and Environmental Science and Engineering. Schrag studies climate and climate change over the broadest range of Earth's history. He has examined changes in ocean circulation over the last several decades, with particular attention to El Niño and the tropical Pacific; he investigates Pleistocene ice-age cycles over the last million years; he studies the warm climates of the Eocene, 50 million years ago; and, with colleagues from Harvard, helped to develop the Snowball Earth hypothesis that explains extreme glacial events that occurred
over 600 million years ago. Currently he is working on the early
history of Mars and Earth, trying to understand the environmental conditions around the time of the origin of life. He is also working on new technological approaches to mitigating future climate change, including advanced energy technologies for low-carbon transportation fuel, and carbon sequestration. Schrag received a B.S. from Yale and a Ph.D. in Geology from the University of California at Berkeley. He taught at Princeton before moving to Harvard in 1997. Among various honors, he was named a MacArthur Fellow in 2000.Location: Henry Salvatori Computer Science Center (SAL) - 101
Audiences: Everyone Is Invited
Contact: Petra Pearce Sapir
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Seminar: Fabrication Methods for the Production of Polymer Films
Thu, Dec 11, 2008 @ 01:00 PM
Mork Family Department of Chemical Engineering and Materials Science
Conferences, Lectures, & Seminars
Mork Family Department of Chemical Engineering and Material Science Presents:"Fabrication Methods for the Production of Polymer Films: Initiated Chemical Vapor Deposition and
Templated Formation of Ionotropic Gels Using Patterned Paper"Malancha Gupta
Harvard University
Cambridge, MAAbstractThis talk will describe two methods for the production of polymer films. The first method focuses on the use of initiated chemical vapor deposition to make a wide variety of polymer coatings such as poly(2-(perfluoroalkyl)ethyl methacrylate), poly(glycidyl methacrylate), and poly(furfuryl methacrylate). Vapor deposition has the environmental benefit of using no solvents and the process can be used to conformally coat substrates with complex geometries such as fabrics and wires since there are no surface tension problems. Deposition rates as high as 300 nm/min can be achieved. The proposed polymerization mechanism is the classical free radical polymerization mechanism of vinyl monomers. Monomer and initiator gases are fed into a vacuum chamber where resistively heated wires are used to thermally decompose the initiator molecules into free radicals. The free radicals then attack the vinyl bonds of the monomer molecules. Propagation occurs on the surface of a cooled substrate. We have demonstrated that the process can be used to modify the surfaces of high-aspect-ratio (~100) polymeric membranes and electrospun fiber mats.The second method focuses on the use of paper templates to fabricate shaped films of ionotropic hydrogels. Solutions of polymers such as alginic acid, carrageenan, and carboxymethyl cellulose form films with defined shapes when brought into contact with patterned templates of paper wetted with aqueous solutions of multivalent cations. This method allows the production of topographically and topologically complex 3D shapes, such as interlocking rings and Möbius strips. The shaped films can be made magnetically responsive by using paramagnetic ions like holmium as the cross-linking ions or by suspending ferrite microparticles in the hydrogels. Heterogeneous films of ionotropic hydrogels can be fabricated through the use of multiple templates. These heterogeneous structures include single films where a pattern of one hydrogel is surrounded by another hydrogel ("gel-in-gel" structures) and hydrogels that contain a gradient in the concentration of cross-linking agent.
Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116
Audiences: Everyone Is Invited
Contact: Petra Pearce Sapir