Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session A32: Focus Session: Crystallization and Directed Assembly of Multicomponent Systems |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Christopher Li, Drexel University Room: 340 |
Monday, March 18, 2013 8:00AM - 8:36AM |
A32.00001: Kinetically Trapped Morphologies in Organic Photovoltaics Invited Speaker: Thomas Russell Controlling the morphology in the active layer of organic photovoltaic (OPV) devise is key in optimizing the performance. To this end, bicontinuous morphologies with characteristic length scales of several tens of nanometers of the electron and hole conducting materials, where the order and orientation of both components are optimized to absorb light over the broadest possible range of the visible spectrum and to transport holes and electrons, after exciton dissociation, Yet, these morphologies are trapped in morphologies that are far removed from equilibrium where multiple kinetic processes, including ordering, phase separation, and the segregation of components to interfaces are arrested as solvent, co-solvents and additives are removed during the preparation of the active layer. Time resolved hard x-ray scattering, resonance soft x-ray scattering and high resolution transmission electron microscopy, along with mobility and transport measurements, have been used to understand the parameters that lead to the development of and can be used to control the morphology of the active layers. In addition, by using ternary mixtures of two polymers active in different parts of the solar spectrum along with an electron transporting material, like PCBM, morphologies can be developed to further enhance the efficiency of these devices. [Preview Abstract] |
Monday, March 18, 2013 8:36AM - 8:48AM |
A32.00002: ABSTRACT WITHDRAWN |
Monday, March 18, 2013 8:48AM - 9:00AM |
A32.00003: Polythiophene-CdSe Nanorod Assembly Using Electric Field Sirinya Chantarak, Todd Emrick, Thomas P. Russell We report controlled solvent evaporation and electric-field assisted vertical alignment of CdSe nanorods (NRs) in a poly(3-hexylthiophene) (P3HT) matrix over large micron areas. NRs of well-defined sizes were synthesized to optimize the geometries of devices made from these nanorods. Regioregular P3HT chains and oligothiophene were functionalized with ligating end-groups to provide contact to the NRs. Hexagonal arrays of these nanocomposites were characterized by transmission electron microscopy (TEM). [Preview Abstract] |
Monday, March 18, 2013 9:00AM - 9:12AM |
A32.00004: SANS and SAXS Studies of DNA-Templated Silver Nanoclusters Hongyu Guo, Sunil K. Sinha, Jaswinder Sharma, Jennifer S. Martinez, Andrew P. Shreve Due to the high affinity of silver cations (Ag+) for DNA bases, following reduction of the Ag+, silver atoms may form short oligonucleotide-encapsulated Ag nanoclusters ($<$1 nm) without the formation of large particles. Such DNA-templated silver nanoclusters have received significant attention as potential fluorescent labels due to their useful properties, including high molar absorptivities, good quantum yields and photostability, and small size. It is thus of great interest to find out the configuration of the Ag nanoclusters which associate with the DNA strands. We have conducted Small Angle Neutron Scattering (SANS) and X-ray Scattering (SAXS) experiments to investigate the formation of the Nanoclusters. By comparing SANS and SAXS data from conjugated samples, pure DNA and DNA/Ag complex, we can characterize the size and position of the Ag clusters along the DNA strand. The time evolution of the DNA/Ag complex can also be studied and can be understood as due to silver oxidation, reduction, or regrouping. We find that the formation and aging of the Ag Nanoclusters are also strongly dependent on the DNA template sequence. [Preview Abstract] |
Monday, March 18, 2013 9:12AM - 9:24AM |
A32.00005: Polymer Crystallization at Curved Liquid-Liquid Interface Christopher Li, Wenda Wang, Hao Qi, Ziyin Huang Curved space is incommensurate with typical ordered structures with three-dimensional (3D) translational symmetry. However, upon assembly, soft matter, including colloids, amphiphiles, and block copolymers (BCPs), often forms structures depicting curved surface/interface. Examples include liposomes, colloidosomes, spherical micelles, worm-like micelles, and vesicles (also known as polymersomes). For crystalline BCPs, crystallization oftentimes overwrites curved geometries since the latter is incommensurate with crystalline order. On the other hand, twisted and curved crystals are often observed in crystalline polymers. Various mechanisms have been proposed for these non-flat crystalline morphologies. In this presentation, we will demonstrate that curved liquid/liquid (L/L) interface can guide polymer single crystal growth. The crystal morphology is strongly dependent on the nucleation mechanism. A myriad of controlled curved single crystals can be readily obtained. [Preview Abstract] |
Monday, March 18, 2013 9:24AM - 9:36AM |
A32.00006: Dynamic Temperature Gradient Effects on Directed Self Assembly of Thin Films of Block Copolymer/Au Nanoparticle Multicomponent Systems Ren Zhang, Gurpreet Singh, Alei Dang, Michael Bockstaller, Alamgir Karim The influence of temperature and Au nanoparticle (NP) concentration on the morphology and properties of poly(styrene-b-methylmethacrylate) (PS-PMMA) block copolymer (BCP) thin films (thickness 80100nm) were investigated. The Au core was grafted with thiol-terminated polystyrene to ensure the preferential interaction to the PS domains. The concentration of Au NPs was varied between 0-10{\%} with respect to PS-PMMA by weight. To induce microphase separation, both static oven annealing and a dynamic thermal field termed cold zone annealing (CZA) were performed. At low temperature annealing (\textless\ 150$^{\circ}$C), horizontal cylindrical morphologies were observed, while at high temperature annealing (150-210$^{\circ}$C), an orientation transition of cylindrical microdomains from vertical to horizontal were observed with increasing Au NPs concentration coupled with an increase in reflective index. The morphology transition is attributed to the decreased thermal conductivity caused by the increasing heterogeneity and growing number of scattering centers. Additionally, we demonstrate unidirectional alignment of BCP/Au NP domains by a novel modification of the CZA method. The dispersion of Au NPs was investigated via TEM and AFM. [Preview Abstract] |
Monday, March 18, 2013 9:36AM - 9:48AM |
A32.00007: A Study on the Packing and Phase Separation of Dissimilar Nanoparticles Xiaobo Shen, Dong Wang, Dhandapani Venkataraman, Tadafumi Adschiri, Ken Nakajima, Thomas Russell To develop a novel approach for the preparation of organic photovoltaic active layer using binary functional nanoparticle assemblies, the nature and characteristics of the interactions and packing between dissimilar nanoparticles must be understood. Here, polymer-based, namely polystyrene (PS), and inorganic-based, namely zinc oxide (ZnO) and titanium oxide (TiO2), nanoparticles are prepared by miniemulsion and hydrothermal reaction methods, respectively. Different functionalities on the particle surface are imparted by further functionalization. The binary assembly of the dissimilar particles is carried out in a variety of ways including solution mixing, non-solvent precipitation, thermal- and solvent annealing, etc. and characterized by Force Volume-AFM (FV-AFM), SEM, TEM and GISAXS techniques. The resulting packing and segregation of the dissimilar particles are shown to be effectively dependent on the molecular weight, inter-particle interactions, particle aspect ratios and sizes, etc. [Preview Abstract] |
Monday, March 18, 2013 9:48AM - 10:00AM |
A32.00008: Self-Assembly of Giant Molecular Shape Amphiphiles based on Polystyrene Tethered Hydrophilic POSS/C$_{60}$ Nanoparticles Xinfei Yu, I-Fan Hsieh, Kan Yue, Wen-Bin Zhang, Stephen Cheng Giant molecular shape amphiphiles (GMSAs) are molecules with two blocks which have different chemical properties and shapes. These molecules are precisely synthesized by controlled/living polymerization and ``click'' chemistry. Self-assembly behaviors of GMSAs are explored in solution, bulk, and thin film states. Micelles (spheres, cylinders, and vesicles) are obtained in the solutions, which are controlled by molecular topology, polymer length, and solvent properties. Nanophase separated structures at 10 nm scale are obtained in the bulk state, which are dependent on volume fractions of each block as well as molecular topology. The nanophase separated structures of GMSAs in the bulk state imply their potential applications in thin-film nano-patterning. Compared with traditional block copolymers, the shape-persistent feature of the molecular nanoparticles might help to reduce the line-edge roughness. Shape and interactions are conclude as two important factors to determine the self-assembly of these molecules. [Preview Abstract] |
Monday, March 18, 2013 10:00AM - 10:12AM |
A32.00009: Self-assembly of ABA amphiphilic block copolymers and its metastable behavior Wei Jiang Amphiphilic triblock copolymer can self-assemble into a vast variety of micelles in selective solvents. We investigated, both theoretically and experimentally, the kinetics of the vesicle formation of ABA amphiphilic triblock copolymers in a selective solvent by cooling the system from an initially homogeneous state at different rates. It was found that the pathway of spontaneous vesicle formation depended on the cooling rate. This road path difference for vesicle formation can be attributed to the existence of many metastable states in the system. Moreover, it was found that in uniform shear flow, the size distribution of the vesicles was much narrower than that in nonuniform shear flow and the uniformity of the vesicles increased with increasing shear rate. The results show that the metastable states in the system can be modulated and the morphological polydispersity of amphiphilic ABA triblock copolymer vesicles can be controlled by shear flow. [Preview Abstract] |
Monday, March 18, 2013 10:12AM - 10:24AM |
A32.00010: ABSTRACT WITHDRAWN |
Monday, March 18, 2013 10:24AM - 10:36AM |
A32.00011: Phase Separation in a Dynamically Asymmetric Polymer Blend: a Stepwise Growth Mechanism Charles Han, Weichao Shi Phase separation dynamics of a polymer blend can be mediated under competition between thermodynamic perturbation and asymmetric viscoelasticity due the contrast in the glass transition temperatures of the two polymer components. The viscous fluidic and soft elastic properties will meet in the phase separation dynamics in this study. Between the two cases, we further revealed a stepwise concentration growth phenomenon, which consists of two individual growths and a ``frozen'' period in between. This stepwise growth should be a general mechanism for asymmetric polymer blends. [Preview Abstract] |
Monday, March 18, 2013 10:36AM - 10:48AM |
A32.00012: Rigid Amorphous Fraction in PLA Electrospun Fibers Peggy Cebe, Qian Ma, Erika Simona Cozza, Marek Pyda, Bin Mao, Yazhe Zhu, Orietta Monticelli Electrospun fibers of poly(lactic acid) (PLA) were formed by adopting a high-speed rotating wheel as the counter-electrode. The molecular orientation, crystallization mechanism, and phase structure and transitions of the aligned ES fibers were investigated. Using thermal analysis and wide angle X-ray scattering (WAXS), we evaluated the confinement that exists in as-spun amorphous, and heat-treated semicrystalline, fibers. Differential scanning calorimetry confirmed the existence of a constrained amorphous phase in as-spun aligned fibers, without the presence of crystals or fillers to serve as fixed physical constraints. Using WAXS, for the first time the mesophase fraction, consisting of oriented amorphous PLA chains, was quantitatively characterized in nanofibers. [Preview Abstract] |
Monday, March 18, 2013 10:48AM - 11:00AM |
A32.00013: Diameter-Dependent Modulus and Melting Behavior in Electrospun Semicrystalline Polymer Fibers Ying Liu, Shuang Chen, Eyal Zussman, Chad Korach, Wei Zhao, Yichen Guo, Miriam Rafailovich Confinement of the semicrystalline polymers, poly-(ethylene-co-vinyl acetate) (PEVA) and low-density polyethylene (LDPE), produced by electrospinning has been observed to produce fibers with large protrusions, which have not been previously observed in fibers of comparable diameters produced by other methods. SAXS spectra confirmed the crystalline structure and determined that the lamellar spacing was almost unchanged from the bulk. Measurement of the mechanical properties of these fibers, by both shear modulation force microscopy (SMFM) and atomic force acoustic microscopy (AFAM), indicates that the modulii of these fibers increases with decreasing diameter, with the onset at $\sim $10 $\mu $m, which is an order of magnitude larger than previously reported. Melting point measurements indicate a decrease of more than 7{\%} in Tm/T$_{\mathrm{0}}$ (where Tm is the melting point of semicrystalline polymer fibers and T$_{\mathrm{0}}$ is the melting point of the bulk polymer) for fibers ranging from 4 to 10 $\mu $m in diameter. The functional form of the decrease followed a universal curve for PEVA, when scaled with T$_{\mathrm{0}}$. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700