Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session A50: Focus Session: Beyond the Gyroid: Complex Network Phases in SelfAssembled Soft Materials 
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Sponsoring Units: GSOFT DPOLY Chair: Gerd SchroederTurk, FriedrichAlexander Universitat ErlangenNurnberg Room: 218 
Monday, March 2, 2015 8:00AM  8:36AM 
A50.00001: Multiple networks in soft materials: polycontinuity Invited Speaker: Stephen Hyde Bicontinuous network phases contain a pair of interwoven labyrinths. Analogous patterns with 3,4, .., 8, .., 54,... labyrinths are readily constructed via 2d hyperbolic geometry. Some of these have been realised in synthetic materials, from mesoporous silicates and lyotropic liquid crystals to metalorganic frameworks. We stumbled on polycontinuous forms while exploring 2d hyperbolic geometry.\footnote{Eur Phys J B, 16, 613630 (2000)} The only known tricontinuous phase found to date in mesoscale selfassembled materials was described via 2d noneuclidean geometry\footnote{Curr Opinion Coll Interf Sci, 8, 514 (2003)} many years before its discovery.\footnote{Nat Chem 1, 123–127 (2009)} This example demonstrates the relevance of regular patterns in noneuclidean 2d spaces to selfassembled morphologies in actual materials. One route to explicit groundup design of mesoscale polycontinuous phases is via starshaped molecules with immiscible arms, such as Yshaped ``polyphiles.'' Some results of theoretical geometric modelling,\footnote{Acta Cryst, A69, 241261 (2013)} simulation\footnote{Proc Natl Acad Sci. USA, 111, 1271–1276 (2014)} and experimental formulation of lyotropic LC mesophases with polyphiles\footnote{Chem Mat, in press (2015); in preparation} will be discussed. [Preview Abstract] 
Monday, March 2, 2015 8:36AM  8:48AM 
A50.00002: Hard Spheres on the Primitive Surface Tomonari Dotera, Yusuke Takahashi Recently hierarchical structures associated with the gyroid in several softmatter systems have been reported [1,2]. One of fundamental questions is regular arrangement or tiling on minimal surfaces [3]. We have found certain numbers of hard spheres per unit cell on the gyroid surface are entropically selforganized [4,5]. Here, new results for the primitive surface are presented. 56/64/72 per unit cell on the primitive minimal surface are entropically selforganized. Numerical evidences for the fluidsolid transition as a function of hard sphere radius are obtained in terms of the acceptance ratio of Monte Carlo moves and order parameters. These arrangements, which are the extensions of the hexagonal arrangement on a flat surface, can be viewed as hyperbolic tiling on the Poincar\'{e} disk with a negative Gaussian curvature. \\[4pt] [1] Y. Matsushita, K. Hayashida, T. Dotera and A. Takano, J. Phys. Condense Matt. 23, 284111 (2011).\\[0pt] [2] T. Castle, M. Evans, S. Hyde, S. Ramsden, V. Robins, Interface Focus 2, 529 (2012).\\[0pt] [3] J. J. K. Kirkensgaard, M. E. Evans, L. de Campo, and S. T. Hyde, Proc. Nat. Acad. Sci. 111, 1271 (2014).\\[0pt] [4] T. Dotera and J. Matsuzawa, Kokyuroku, RIMS, Kyoto Univ., 1725, 80 (2011).\\[0pt] [5] T. Dotera, M. Kimoto, J. Matsuzawa, Interface Focus 2, 575 (2012). [Preview Abstract] 
Monday, March 2, 2015 8:48AM  9:00AM 
A50.00003: Real time SANS studies on the transformation between the hexagonal cylinder phase and the bicontinuous gyroid structure: transient structures Kell Mortensen, Martin Vigild, Ruya Eskimergen Combined application of SANS and oscillatory shear is effective tools for studying structure and realtime dynamics of soft matter materials. Largeamplitude oscillatory shear can be used to effectively control the texture of soft materials in the ordered states. We will show experimental data proving that the 10spot pattern often characterizing the gyroid phase of block copolymer melts as well as surfactant systems is a 2D powderpattern, originating from the dominating structure of the cylinder axis when grown from singledomain hexagonal structures. We show that the gyroid state is unstable when exposed to large amplitude / large frequency shear, transforming into the a hexagonal cylinder phase.\footnote{Eskimergen et al., \textbf{Macromol} 38, 1286 (2005)} The transformation is completely reversibly. With the slow kinetics, it is possibly in detail to follow the complex materials transformation from onedimensional cylinders to the complex threedimensional gyroid phase of block copolymers. The transformation kinetics is different within the various crystallographic directions, and shows the transformation through a transient structure rather similar to that found in SCFTstudies.\footnote{Mortensen et al, unpubl.}$^,$\footnote{Ly et al. \textbf{Macromol} 40, 2928 (2007)}. [Preview Abstract] 
Monday, March 2, 2015 9:00AM  9:12AM 
A50.00004: Toward complex network droplets  a computational study of bicontinuous network regions in star polymer droplets Ryan Marson, Sharon Glotzer The complexity and functionality of network phases in soft matter systems offer a wealth of possible technological applications ranging from photonics to medicine. Through Dissipative Particle Dynamics (DPD) simulations, with explicit solvent, of over 1 million particles we demonstrate control of nano and micro scale ordering in star polymer droplets. By tuning the building block geometry and interactions between star polymer components we produce a droplet phase diagram. In particular we highlight regions of the structure that contain phase separated bicontinuous network domains. This system demonstrates the possibility of functional droplets composed of complex networks, with a hierarchy of scales that can be tuned for specific applications. [Preview Abstract] 
Monday, March 2, 2015 9:12AM  9:24AM 
A50.00005: Free EnergyBased Monte Carlo Determination of a Model Microphase Former Yuan Zhuang, Kai Zhang, Patrick Charbonneau Determining the equilibrium phase behavior of microphase formers from particlebased simulations is particularly challenging because the occupancy of the various microphase features (clusters, layers, cylinders, etc.) fluctuates and varies from one state point to the next. Here, we compute the phase diagram of a schematic microphase former, the square welllinear model, using a novel free energybased Monte Carlo simulation methodology. Our approach surmounts traditional equilibration difficulties by including modulated reference fields and developing the expanded isothermalisobaric [N]PT ensemble. Our results for the squarewelllinear model goes beyond other descriptions of the equilibrium phase behavior of simple microphase formers by revealing the complex thermodynamic interplay of various microphases with micelle formation and percolation. [Preview Abstract] 
Monday, March 2, 2015 9:24AM  9:36AM 
A50.00006: Structural Diversity of SelfAssembled Iridescent Arthropod Biophotonic Nanostructures Vinod Kumar Saranathan, Richard O. Prum Many organisms, especially arthropods, produce vivid interference colors using diverse mesoscopic (100350 nm) integumentary biophotonic nanostructures that are increasingly being investigated for technological applications. Despite a century of interest, we lack precise structural knowledge of many biophotonic nanostructures and mechanisms controlling their development, when such knowledge can open novel biomimetic routes to facilely selfassemble tunable, multifunctional materials. Here, we use synchrotron small angle Xray scattering and electron microscopy to characterize the photonic nanostructure of 140 iridescent integumentary scales and setae from ~127 species of terrestrial arthropods in 85 genera from 5 orders. We report a rich nanostructural diversity, including triplyperiodic bicontinuous networks, closepacked spheres, inverse columnar, perforated lamellar, and disordered spongelike morphologies, commonly observed as stable phases of amphiphilic surfactants, block copolymer, and lyotropic lipidwater systems. Diverse arthropod lineages appear to have independently evolved to utilize the selfassembly of infolding bilayer membranes to develop biophotonic nanostructures that span the phasespace of amphiphilic morphologies, but at optical length scales. [Preview Abstract] 
Monday, March 2, 2015 9:36AM  9:48AM 
A50.00007: The Tricontinuous 3ths(5) Phase: A New Morphology in Copolymer Melts Michael Fischer, Liliana de Campo, Jacob Kirkensgaard, Stephen Hyde, Gerd SchroederTurk Selfassembly remains one of the most efficient routes to the formation of ordered nanostructures, including the double gyroid network phase in diblock copolymers based on two intergrown network domains. This talk demonstrates the use of selfconsistent field theory to show that a tricontinuous structure with monoclinic symmetry, called 3ths(5), based on the intergrowth of three distorted ths nets, is an equilibrium phase of triblock starcopolymer melts when an extended molecular core is introduced. The introduction of the core enhances the role of chain stretching by enforcing larger structural length scales, thus destabilizing the hexagonal columnar phase in favor of morphologies with less packing frustration. This study further demonstrates that the introduction of molecular cores is a general concept for tuning the relative importance of entropic and enthalpic free energy contributions, hence providing a tool to stabilize an extended repertoire of selfassembled nanostructured materials. [Preview Abstract] 
(Author Not Attending)

A50.00008: Group Theory of CircularPolarisation Effects in Chiral Photonic Crystals with FourFold Rotation Axes, Applied to the EightFold Intergrowth of Gyroid Nets Matthias Saba, Mark D. Turner, Klaus Mecke, Min Gu, Gerd E. Schr\"oderTurk The \emph{8srs PhC} of bodycentered cubic $I432$ symmetry consists of eight interwoven equalhanded dielectric Gyroid networks embedded in air. We use representation theory and scattering matrix calculations to derive analytical results for the band structure topology and the circular polarization scattering parameters of the 8srs PhC and any other lossless $I432$ photonic crystal. All results are supported by numerically. We demonstrate in particular that all bands along the cubic $[100]$ direction can be identified with the irreducible representations $E_\pm$, $A$ and $B$ of the $C_4$ point group. The $E_+$ ($E_$) representation can be identified as the only transmission channel for right(left)circularly polarized light. We derive explicit relationships for the (zero Bragg order) transmission and reflectance amplitudes which guarantee equal transmission rates for both polarizations and vanishing ellipticity below a critical frequency, yet allowing for finite rotation of the polarization plane. The combination of vanishing losses, vanishing ellipticity, nearperfect transmission and optical activity comparable to that of metallic metamaterials makes this geometry an attractive design for nanofabricated photonic materials. [Preview Abstract] 
Monday, March 2, 2015 10:00AM  10:12AM 
A50.00009: Tuning Lyotropic Liquid Crystalline Phase Behavior of Gemini Surfactants by Linker Parity Dominic Perroni, Carlos BaezCotto, Sriteja Mantha, Gregory Sorenson, Arun Yethiraj, Mahesh Mahanthappa Aqueous bicontinuous lyotropic liquid crystals (LLCs) derived from small molecule surfactants are useful nanostructured materials with myriad applications, in fields ranging from structural biology to membrane science. However, access to these coveted phases is limited by the fact that few surfactant platforms readily stabilize these network phases over the wide amphiphile concentration and temperature phase windows necessary for their widespread applications. We have recently shown that gemini (``twin tail'') dicarboxylate surfactants, comprising two single tail amphiphiles covalently linked near the headgroup by a hydrophobic bridge, exhibit a greatly increased propensity to form stable double gyroid LLC phases. In this presentation, we will demonstrate the unusual sensitivity of gemini dicarboxylate surfactant lyotropic selfassembly to the length of the hydrophobic bridge: oddcarbon linkers produce stable double gyroid phases over amphiphile composition windows as wide as 40 wt{\%} that are stable between $T = $ 22100 $^{\circ}$C. We rationalize these results in terms of the detailed molecular conformations of the surfactants that stem from the length of the bridging moiety, which suggests that this molecular design strategy may generally extend to other surfactant classes. [Preview Abstract] 
Monday, March 2, 2015 10:12AM  10:24AM 
A50.00010: Mechanical enhancement through phase separation in a bicontinuous hydrogel network Ryan Nixon, Thomas Angelini Bicontinous networks of phase separated polymers are often used in biomedical materials to control the spatial distribution of multiple surface functionalities. Here we describe a different use of phase separation, which leverages a balance of aggregating and swelling tendencies of the two separated components, producing a hydrogel that is highly stretchable and resilient after large extensions. In contrast to the typical onecomponent hydrogel, which is brittle and weak, the twocomponent microphase separated hydrogel recovers within just a few minutes after being stretched by several hundred percent, and fails at about 1000\% strain. Our preliminary 3D reconstructions of the bicontinuous phases suggest that the gel's material properties arise from a systemspanning network of nonspecific hydrophobic bonds that can be broken and reformed under cycles of large strain, while elasticity is provided by the highlysolvated hydrogel that makes up the complementary phase. [Preview Abstract] 
Monday, March 2, 2015 10:24AM  10:36AM 
A50.00011: Polycontinuous Lyotropic Liquid Crystalline Network Phases from Gemini Dicarboxylate Surfactants Mahesh Mahanthappa, Gregory Sorenson, Adam Schmitt Arising from the water concentrationdependent selfassembly of amphiphilic molecules, lyotropic liquid crystals (LLCs) form a wide variety of structurally periodic nanoscale morphologies including discontinuous micellar phases (I), hexagonallypacked cylinders (C), and lamellar (L) phases. In intermediate amphiphile concentration windows between the L and C phases, one typically observes three bicontinuous cubic network phases: gyroid (G), diamond (D), and primitive (P). Recent theoretical work has suggested the possible stability of a variety of noncubic network phase LLCs, yet none of these phases have been previously observed. In this presentation, we describe the experimental discovery of the first triply periodic network phase LLC with 3Dhexagonal symmetry (space group {\#}193) in binary mixtures of water with a simple gemini dicarboxylate surfactant based on dodecanoic acid. Using a combination of SAXS and rheological methods, we structurally characterize this new phase and show that it is comprised of three interpenetrating lipidic networks of 3fold connectors in a matrix of water. This finding highlights the unusual aqueous phase behavior of gemini surfactants and suggests new methods for discovering and stabilizing new network phase LLCs beyond the gyroid. [Preview Abstract] 
Monday, March 2, 2015 10:36AM  10:48AM 
A50.00012: Deformations of the gyroid and Lidinoid minimal surfaces using flat structures Adam Weyhaupt Mathematically, the challenge in proving the existence of a purported triply periodic minimal surface is in computing parameter values that depend on a system of equations defined by elliptic integrals. This is generally very difficult. In the presence of some symmetry, however, a technique developed by Weber and Wolf can reduce these elliptic integrals to basic algebra and geometry of polygons. These techniques can easily prove the existence of some surfaces and the presence of a family of solutions. Families of surfaces are important mathematically, but recent work by Seddon, et. al., experimentally confirms that these families of surfaces can occur physically as well. In this talk, we give a brief overview of the technique and show how it can be applied to prove the existence of several families of surfaces, including lower symmetry variants of the gyroid and Lidinoid such as the rG, rPD, tG, and rL. We also conjecture a map of the moduli space of triply periodic minimal surfaces of genus 3. [Preview Abstract] 
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