Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session W14: Invited Session: Patterns in Polymers: Elasticity, Fluids, and Surfaces |
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Sponsoring Units: DPOLY GSNP Chair: Kari Dalnoki-Veress, McMaster University Room: 301-303 |
Thursday, March 6, 2014 2:30PM - 3:06PM |
W14.00001: Exotic nanoparticles with block copolymer design and solution construction with kinetic control Invited Speaker: Darrin Pochan Kinetic pathways and long temporal stabilities of different block copolymer micelles and nanoscale aggregates have been used to construct exotic nanoparticles in solution. Due to low chain exchange dynamics between block copolymeric micelles and solvent, global thermodynamic equilibrium is extremely difficult, if not impossible, to achieve in block copolymer assembly. However, by taking advantage of this slow kinetic behavior of polymeric micelles in solution, one can purposely produce multicompartment nanoparticles and mulitgeometry nanoparticles by forcing different block copolymers to reside in the same nanoscale structure through kinetic processing. While kinetically trapped in common nanostructures, local phase separation can occur producing compartments and surface patches uniquely displayed from the surface of the nanoparticle. This compartmentalization can be used within common micelle geometries to make complex spheres and cylinders or can be used to make new nanostructures such as multigeometry aggregates such hybrid cylinder-sphere aggregates, disk-cylinder nanoparticles, and hybrid inorganic-block copolymer nanoparticles. Additional results producing nanoparticles with blends of three or more different block copolymers and block copolymer-polypeptide hybrid particles will be discussed. [Preview Abstract] |
Thursday, March 6, 2014 3:06PM - 3:42PM |
W14.00002: Exploiting Elasticity with Thin Polymer Films Invited Speaker: Andrew Croll Soft matter is often dominated by long-ranging mechanical distortion and is thus intimately linked to elastic theory. The detailed understanding provided by theory has allowed remarkable technological achievements to be made with polymers and other soft systems. However, as technology pushes lengthscales downward many challenges have arisen and even basic problems such as measuring Young's modulus become difficult. To move forward, many polymer thin-film researchers have been attracted to the simple repetitive buckling pattern known as wrinkling because the instability provides a convenient tool to measure mechanical properties. As with all technology the wrinkle system does have physical limits on its applicability, several of which may not be obvious and may have implications for extreme measurement. Here we highlight some of our recent work examining the limits of this elastic pattern and the implications for thin polymer films. We first show how the morphology of ultra-thin wrinkled polystyrene and polystyrene-block-poly(2-vinylpyridine) films show signs of localization effects - a clear deviation from linear elasticity. We go on to show how roughness, in certain cases, can induce similar morphologies, even in the limits of vanishing applied stress. As random roughness influences a film's elastic behaviour it is natural to examine periodic roughness as means to control localization and create more complex morphologies. Colloidal polystyrene is an excellent test material as it can easily be assembled in highly ordered crystalline monolayers. Remarkably, this ``discrete'' polymer film shows the same wrinkled morphology as does a continuum film. We show how a completely different type of elasticity is necessary to explain the effect, that of a granular material. More disordered ``glassy'' colloidal monolayers provide a means to push our understanding of the granular elastic theory, and suggest an interesting, albeit highly speculative limit for extreme continuum behaviour. [Preview Abstract] |
Thursday, March 6, 2014 3:42PM - 4:18PM |
W14.00003: Transition Pathways Connecting Stable and Metastable Ordered Phases Invited Speaker: An-Chang Shi Phase transitions are ubiquitous in nature. Understanding the kinetic pathways of phase transitions has been a challenging problem in physics and physical chemistry. From a thermodynamics point of view, the kinetics of phase transitions is dictated by the characteristics of the free energy landscape. In particular, the emergence of a stable phase from a metastable phase follows specific paths, the minimum energy paths, on the free energy landscape. I will describe the characteristics of the minimum energy paths and introduce an efficient method, the string method, to construct them. I will use membranes and block copolymers as examples to demonstrate the power of the method. In particular, I will show how precisely determined transition pathways provide understanding and surprises when we try to connect the different ordered phases. [Preview Abstract] |
Thursday, March 6, 2014 4:18PM - 4:54PM |
W14.00004: Pattern formation and control in polymeric systems: From Minkowski measures to in situ AFM imaging Invited Speaker: Karin Jacobs Thin liquid polymer films are not only of great technical importance, they also exhibit a variety of dynamical instabilities [1]. Some of them may be desired, some rather not. To analyze and finally control pattern formation, modern thin film theories are as vital as techniques to characterize the morphologies and structures in and on the films. Examples for the latter are atomic force microscopy (AFM) as well as scattering techniques [2]. The talk will introduce into the practical applications of Minkowski measures to characterize patterns and explain what thin film properties (e.g. capillary number, solid/liquid boundary condition, glass transition temperature, chain mobility) can further be extracted including new technical possibilities by AFM and scattering techniques [3]. \\[4pt] [1] O. B\"{a}umchen, L. Marquant, R. Blossey, A. M\"{u}nch, B. Wagner and K. Jacobs, ``Influence of slip on the Rayleigh-Plateau rim instability in dewetting viscous films,'' (submitted). \\[0pt] [2] P. Gutfreund, O. B\"{a}umchen, R. Fetzer, D. van der Grinten, M. Maccarini, K. Jacobs, H. Zabel and M. Wolff, ``Solid surface structure affects liquid order at the polystyrene--self-assembled-monolayer interface,'' \textit{Phys. Rev. E }\textbf{87} (2013) 012306. \\[0pt] [3] O. B\"{a}umchen, R. Fetzer, M. Klos, M. Lessel, L. Marquant, H. H\"{a}hl, K. Jacobs, ``Slippage and nanorheology of thin liquid polymer films,'' \textit{J. Phys.:Condens. Matter }\textbf{24} (2012) 325102. [Preview Abstract] |
Thursday, March 6, 2014 4:54PM - 5:30PM |
W14.00005: Nonequilibrium patterns in nanocomposite films and fluids Invited Speaker: Erik K. Hobbie Carbon and silicon impact a broad range of technologies from structural composites to microelectronics. Working at the nanoscale in the colloidal domain, we leverage soft matter to simplify processing and improve the performance of these materials. Our approach, which exploits concepts firmly rooted in polymer science, has potentially profound implications for a number of emerging technologies. Two specific examples will be discussed. In the first, thin films of purified single-wall carbon nanotubes are deposited on elastomer substrates for applications in flexible electronics. By adapting approaches developed to study the elasticity of thin polymer films, we infer the mechanics of the nanotube coatings from the pattern of wrinkles and folds that emerges under compression, and we relate this response to the electronic and optical properties of the films. In the second example, patterns of phase separation in drying nanocrystal-polymer mixtures are explored in the context of achieving homogeneous coatings. The results are interpreted using equilibrium theories of colloid-polymer mixtures coupled with lattice-Boltzmann simulations of drying complex fluids. I will conclude by discussing some examples of how ideas from both of these scenarios are being merged for new applications. [Preview Abstract] |
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