Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E59: Polymer Physics PrizeInvited Prize/Award
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Sponsoring Units: DPOLY Chair: Monica Olvera De La Cruz, Northwestern Univ Room: LACC Petree Hall D |
Tuesday, March 6, 2018 8:00AM - 8:36AM |
E59.00001: Polymer Physics Prize Talk: The interplay between elasticity, defect structure, and motion in active nematic polymers Invited Speaker: Juan de Pablo Polymeric materials that comprise mechano-chemically active components are able to undergo spontaneous structural rearrangements that generate internal stresses and motion. Understanding how internal activity leads to specific behaviors is important for design of autonomous materials systems capable of delivering desired functionalities. This lecture will focus on the relationship between structure, activity, and motion in lyotropic liquid crystalline polymeric systems. More specifically, results will be presented for actin and tubulin suspensions, where activity is generated by protein motors. A distinctive feature of these biopolymers is that characteristic contour lengths can range from hundreds of nanometers to tens of microns, thereby making them amenable for study by optical microscopy. By relying on molecular and meso-scale models, it is possible to arrive at a comprehensive description of these suspensions that helps explain the connections between molecular structure, the formation and shape of distinct topological defects, activity, and defect dynamics. One of the outcomes of such a description is the realization that hydrodynamic interactions can in some cases exacerbate or mitigate the elasticity of the underlying materials, leading to non-intuitive phenomena that do not arise at equilibrium. By balancing such effects, these findings raise the possibility of designing functional materials where specific, macroscopic dynamical responses are engineered into a system. |
Tuesday, March 6, 2018 8:36AM - 9:12AM |
E59.00002: Directed self-assembly in two and three dimensions Invited Speaker: Paul Nealey Directed self-assembly (DSA) is a promising strategy for high-volume cost-effective manufacturing at the nanoscale. Materials that self-assemble form nanostructures with precise, predictable and reproducible dimensions at length scales at the molecular and atomic scale. Unfortunately, the micrometer areas or volumes over which the materials self-assemble with adequate perfection in structure is often incommensurate with the macroscopic dimensions of devices and systems of devices of industrial relevance. Directed self-assembly (DSA) refers to the integration of self-assembling materials with templates to impact structural precision and therefore functionality to self-assembling materials over macroscopic dimensions. Here I will discuss the use of lithographically-defined chemically patterned surfaces to direct the assembly of block copolymers and liquid crystal systems in two and three dimensions for applications in semiconductor manufacturing, ion-conducting membranes, and optoelectronics. In addition, I will highlight the fundamental understanding gained by comparing and contrasting the two materials systems, and how progress in DSA has been enabled and accelerated by a combined experimental and theoretical approach. |
Tuesday, March 6, 2018 9:12AM - 9:48AM |
E59.00003: Using Physical Vapor Deposition to Produce Structured Glasses - from Isotropic to Liquid-Crystalline Order Invited Speaker: Mark Ediger While liquid-cooled glasses are usually isotropic, glasses can be anisotropic and this is typically the case for glasses produced by physical vapor deposition. For organic electronics, glass anisotropy can be manipulated to increase device efficiency. We have shown that the substrate temperature during deposition plays a key role in controlling the anisotropy of vapor-deposited glasses. For hole transport materials such as TPD, mildly anisotropic glasses in which molecules have a tendency to either “lie down” or “stand up” can be prepared, as indicated by ellipsometry and grazing incidence x-ray scattering. For the smectic mesogen itraconazole, a highly ordered smectic monodomain is obtained directly by deposition just below Tg; everywhere in the sample the smectic planes are parallel to the free surface. For discotic mesogens, glasses with highly ordered columnar structures are obtained directly by deposition with substrate temperature allowing a switch between in-plane and out-of-plane columns. Remarkably, molecules with no known liquid-crystalline states can also form glasses with substantial liquid-crystalline order. These developments present significant opportunities to design new anisotropic solids for organic electronics and optoelectronics. |
Tuesday, March 6, 2018 9:48AM - 10:24AM |
E59.00004: Defect motion and annihilation in block copolymers Invited Speaker: Marcus Mueller Directed self-assembly (DSA) of block copolymers for microelectronic device fabrication requires excessively small defect densities. Whereas the excess free energy of a defect in a perfect lamellar structure exceeds by far the thermal energy scale kT, and the equilibrium defect density is vanishingly small, defects are observed in experiments and simulations. Thus, defects occur in the course of the kinetics of structure formation. Using simulations of a soft, coarse-grained model, SCFT calculation and continuum models we study the kinetics of structure formation, defect motion and annihilation, as well as the underlying free-energy landscape. The study identifies optimal conditions for defect free self-assembly and discusses how the guiding structures influence the interaction between defects. The ability of continuum models to describe these phenomena is also critically evaluated. |
Tuesday, March 6, 2018 10:24AM - 11:00AM |
E59.00005: Polymeric Bicontinuous Microemulsions Invited Speaker: Frank Bates A polymeric bicontinuous microemulsion (BmE) contains interpenetrating domains with dimensions ranging from 10 nanometers to 1 micron created by blending appropriate amounts of two incompatible homopolymers with the corresponding diblock copolymer. Previous experiments have identified the BmE in a narrow channel of compositions that separates regions of lamellar (LAM) order and macroscopic phase separation, associated with the weak first-order Brazaovskii and Ising universality classes, respectively. We have explored the phase behavior of a model ternary system comprised of poly(cyclohexylethylene) (PCHE), poly(ethylene) (PE) and the associated PCHE-PE diblock copolymer. Small-angle x-ray scattering, transmission electron microscopy, and optical transmission experiments have precisely located the line of congruent transitions that defines the peak temperature separating the lamellar and disordered states and terminates at the BmE. These results will be discussed in the context of the roles of fluctuation effects and conformational asymmetry in defining interfacial curvature and the structure of the phase prism. |
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