Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session F11: Invited Session: Polymer Physics Prize Session |
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Sponsoring Units: DPOLY Chair: John Torkelson, Northwestern University Room: 310 |
Tuesday, March 19, 2013 8:00AM - 8:36AM |
F11.00001: Polymer Physics Prize Lecture: Self-assemblies of Giant Molecular Shape Amphiphiles as a New Platform for Engineering Structures with Sub-Nanometer Feature Sizes Invited Speaker: Stephen Z.D. Cheng Utilizing nano-building blocks rather than atoms to construct and engineer new structures is a fresh approach to design and develop functional materials for the purpose of transferring and amplifying microscopic functionality to macroscopic materials' property. As one of the important elements of these nano-building blocks, giant molecular shape amphiphiles (GMSAs) provide a latest platform for generating self-assembled ordered structures at nanometer scale, which are stabilized by collective physical bonds (such as collective hydrogen bonding). In this talk, two topics will be focused on. First, composed of functionalized hydrophilic molecular nanoparticles as the heads with rigid shape and fixed volume, and tethered polymer chains as the tails (such as giant molecular surfactants and lipids and other topologies), these GMSAs of various architectures can self-assemble into highly diversified, thermodynamically stable microstructures at sub-10 nm length scale in the bulk, thin film and solution states. Second, GMSAs could also be constructed solely from nanoparticles interconnected via different numbers of the rigid linkages in specific symmetry, simulating the overall shapes of small molecules but with sizes that are one-order of magnitude larger in length and three-order of magnitude larger in volume. Giant crystal structures can then be obtained from this class of ``giant molecules'' via supramolecular crystallization. These findings are not only scientifically intriguing in understanding the physical principles underlying their self-assembly, but also technologically relevant in industrial applications. [Preview Abstract] |
Tuesday, March 19, 2013 8:36AM - 9:12AM |
F11.00002: Polymer Spheulites Invited Speaker: Bernard Lotz The growth and/or structural features that determine lamellar shape in polymer spherulites and therefore their structure and properties have been debated for many years. The spectacular twisting of lamellae in optically banded spherulites has been explained by the existence of unbalanced stresses in opposite fold surfaces of the lamellae. This mechanical origin implying the folds explains also the demonstrated absence of correlation between lamellar twist sense and molecular chirality of chiral polymers. Unbalanced surface stresses may also generate spherulites made of scrolled lamellae, with the scroll axis radial. This original morphology was first observed in spherulites of poly(vinylidene fluoride) in its $\gamma $ phase. It arises from a chemical disparity of folds formed on opposite fold surfaces, the volumes of which differ by 10{\AA}*3. Similar chemical disparities have been suggested to explain the formation of highly unusual scrolled single crystals of polyamide 66 obtained from solution under specific annealing and crystallization conditions. Related thermal histories lead to the formation, in the bulk, of unusual optically negative spherulites of polyamide 66 that were first observed in the 1940s. These still poorly understood negative spherulites may well display a similar scrolled lamellar morphology. The analysis of unbalanced surface stresses requires to evaluate the interplay and mutual impact of crystal and fold structures. The stresses associated with different fold structures are locally small perturbations but are cumulative and are exerted on thin, flexible lamellae. The latter non-planar morphologies reveal these stresses and help reach sub-moleculr insights on the fold structures. [Preview Abstract] |
Tuesday, March 19, 2013 9:12AM - 9:48AM |
F11.00003: Cellulose as Sustainable Materials for Separation Membranes Invited Speaker: Benjamin Chu Polysaccharides, while complex, form one of the most abundant sustainable resources on earth. We want to take advantage of fundamental advances in materials understanding across length and time scales to investigate the interrelationships between structure, morphology, processing, properties, performance, and cost to meet the specific challenges arising from separation membranes for water purification. Non-woven fiber mats have unique properties, such as interconnected pores, a very large surface-to-volume ratio, and a high capacity for surface modifications. The breakthrough concept of combining fibrous mats composed of different fiber diameters for fabricating scaffolds as a unique platform for water purification is presented. Further, we take advantage of recent advances in chemical modifications, structural studies using synchrotron X-rays, and physical scale-up transformations to drastically improve filtration membrane development. [Preview Abstract] |
Tuesday, March 19, 2013 9:48AM - 10:24AM |
F11.00004: Computational Modeling Studies of Peptides and Proteins on Inorganic Surfaces Invited Speaker: Barry Farmer Biological moieties offer exquisite sensitivity and selectivity in their interactions with small molecules, offering considerable potential in applications as chemical sensors. To detect binding events between the peptide and the intended molecule, a transduction mechanism is needed. This often involves an association of the peptide with an inorganic surface, such as a metal nanoparticle, a carbon nanotube, or graphene. Understanding the nature of the association of the peptide with the surface and its effect on the conformational (and thus, binding) properties of the peptide are key to optimizing the sensing mechanism. We utilized computational approaches ranging from \textit{ab initio} to molecular dynamics to bond-fluctuation Monte Carlo methods to study the adsorption of peptides and proteins on inorganic surfaces to develop an understanding of the role that composition and substrate character plays in the adsorption process, and in turn, the effects on the binding events with the molecules of interest. [Preview Abstract] |
Tuesday, March 19, 2013 10:24AM - 11:00AM |
F11.00005: Periodic Polymers Invited Speaker: Edwin Thomas Periodic polymers can be made by self assembly, directed self assembly and by photolithography. Such materials provide a versatile platform for 1, 2 and 3D periodic nano-micro scale composites with either dielectric or impedance contrast or both, and these can serve for example, as photonic and or phononic crystals for electromagnetic and elastic waves as well as mechanical frames/trusses. Compared to electromagnetic waves, elastic waves are both less complex (longitudinal modes in fluids) and more complex (longitudinal, transverse in-plane and transverse out-of-plane modes in solids). Engineering of the dispersion relation between wave frequency w and wave vector, k enables the opening of band gaps in the density of modes and detailed shaping of w(k). Band gaps can be opened by Bragg scattering, anti-crossing of bands and discrete shape resonances. Current interest is in our group focuses using design - modeling, fabrication and measurement of polymer-based periodic materials for applications as tunable optics and control of phonon flow. Several examples will be described including the design of structures for multispectral band gaps for elastic waves to alter the phonon density of states, the creation of block polymer and bicontinuous metal-carbon nanoframes for structures that are robust against ballistic projectiles and quasi-crystalline solid/fluid structures that can steer shock waves. [Preview Abstract] |
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