Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session G34: Polymer Blends |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Julie Albert, North Carolina State University Room: 342 |
Tuesday, March 19, 2013 11:15AM - 11:27AM |
G34.00001: An unusual route to develop poly(lactic acid) based materials with deformation-recovery properties Sahas Rathi, David Ng, E. Bryan Coughlin, Shaw Hsu, Charles Golub, Gerald Ling, Mike Tzivanis A novel method based on co-crystallizing polymer blends was developed to obtain Poly(lactic acid) (PLA) based materials with deformation recovery properties. Two sets of blends were studied. One based on the PDLA-soft polymer-PDLA triblock copolymer and PLLA, where D and L refer to the two chiral isomers of PLA, while the other was based on homopolymer blends of PDLA/soft polymer/PLLA having identical chemical composition. The mechanical properties and morphological features of the two sets of blends were completely different. The triblock copolymer/ PLLA blends gave rise to flexible, tough semicrystalline materials while the corresponding homopolymer blends exhibited very low strains at break and high dissipative/dampening properties. The drastically different stereocomplex crystallization kinetics in the two sets of blends led to interspherulitic segregation of the amorphous chains in the triblock blends while intraspherulitic segregation occurred in the homopolymer blends. The presence of significant connectivity between the stereocomplex crystallites formed, in the triblock copolymer/ PLLA blends, was important for the deformation shape recovery characteristics observed. In addition, it was found that the use of ether-ester based plasticizers significantly reduced the glass transition temperature and enhanced the recovery property of the triblock copolymer based PLA blends. [Preview Abstract] |
Tuesday, March 19, 2013 11:27AM - 11:39AM |
G34.00002: Nanoporous polystyrene samples through the selective removal of low-Mw component in PS/PS blend samples James Forrest, Chad Daley, Sonia Zhang, Sharon Yang, Stefan Idziak We present here a novel technique for producing low density nanoporous polystyrene samples. The method hinges upon the ability to selectively dissolve away the low-M$_w$ component from blend samples which consist of high- and low-M$_w$ atactic polystyrenes with drastically different M$_w$'s. Given the chemical similarity between the two components it is possible to prepare blend samples while avoiding microscopic phase separation. Removal of the low-M$_w$ component then leaves behind a sample with nanoscopic voids on the order of 10's of nm. This is in contrast to porous polymer materials prepared through the removal of chemically distinct polymer species, where larger scale pores are the end result. Tuning of the initial fraction of the low-M$_w$ component allows for variation in the density of the porous material; ellipsometric measurements indicate samples with densities lower than 0.5 g/cm$^3$. Characterization of the samples using ellipsometry, AFM, and X-ray diffraction will be discussed. [Preview Abstract] |
Tuesday, March 19, 2013 11:39AM - 11:51AM |
G34.00003: Effect of critical molecular weight of PEO in epoxy/EPO blends as characterized by advanced DSC and solid-state NMR Xiaoliang Wang, Shoudong Lu, Pingchuan Sun, Gi Xue The differential scanning calorimetry (DSC) and solid state NMR have been used to systematically study the length scale of the miscibility and local dynamics of the epoxy resin/poly(ethylene oxide) (ER/PEO) blends with different PEO molecular weight. By DSC, we found that the diffusion behavior of PEO with different Mw is an important factor in controlling these behaviors upon curing. We further employed two-dimensional 13C-\textbraceleft 1H\textbraceright PISEMA NMR experiment to elucidate the possible weak interaction and detailed local dynamics in ER/PEO blends. The CH2O group of PEO forms hydrogen bond with hydroxyl proton of cured-ER ether group, and its local dynamics frozen by such interaction. Our finding indicates that molecular weight (Mw) of PEO is a crucial factor in controlling the miscibility, chain dynamics and hydrogen bonding interaction in these blends. [Preview Abstract] |
Tuesday, March 19, 2013 11:51AM - 12:03PM |
G34.00004: Effect of Supercritical Carbon Dioxide on Polymer Blend Miscibility Nicholas Young, Sebnem Inceoglu, Andrew Jackson, Stephane Costeaux, Nitash Balsara Supercritical fluids have been investigated as environmentally benign solvents for the processing of polymers on the industrial scale. In this work, we study the effect of supercritical carbon dioxide (scCO$_{\mathrm{2}})$ on the phase behavior of a blend of a random copolymer and a homopolymer. Styrene-acrylonitrile copolymer (SAN) and poly(methyl methacrylate) (PMMA) are known to display lower critical solution temperature-type phase behavior, undergoing a transition from a homogeneous mixture to a phase-separated blend upon heating. Depending on certain parameters such as SAN composition (w$_{\mathrm{AN}})$ and blend fraction ($\phi_{\mathrm{SAN}})$, the miscibility window for the two polymers can be tuned over a significant temperature range by introducing scCO$_{\mathrm{2}}$ into the system. Using small angle neutron scattering, the thermodynamic interactions between SAN and PMMA as described by the Flory-Huggins parameter $\chi $ are shown to be strongly dependent on scCO$_{\mathrm{2}}$ activity. [Preview Abstract] |
Tuesday, March 19, 2013 12:03PM - 12:15PM |
G34.00005: Microphase-Separated Structures of Gold Nanoparticle Grafted with Two Immiscible Polymers Daisuke Kawaguchi, Tatsuhiro Nakano, Yushu Matsushita It is important to control structures of organic-inorganic hybrid materials to make functional devices. If gold-nanoparticle (AuNP) grafted with two immiscible polymers can self-assemble into microphase-separated structures, it can be expected that AuNP arranges on their own microphase-separated interface in nanometer scale. In this study, we prepared AuNP grafted with polyisoprene (PI) and polystyrene (PS) which were immiscible polymers and investigated their microphase-separated structures by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The AuNP complexes form various microphase-separated structures such as lamellar, cylindrical and spherical structures with changing polymeric composition. The TEM image and SAXS profile for the AuNP complexes for the symmetric composition shows that PS and PI form lamellar structures and the AuNPs are forced into the PS/PI interface. [Preview Abstract] |
Tuesday, March 19, 2013 12:15PM - 12:27PM |
G34.00006: Improving the Compatibility between Polystyrene and Polybutadiene by Adding Silica Nanoparticles Yuping Xie, Damien Maillard, Sanat Kumar, Brandon Cash, Brian Benicewicz The compatibility between polystyrene (PS) and polybutadiene (PB) was improved by adding bare silica or PS-grafted silica nanoparticles. The grafting density varies from 0.01 chains/nm$^{2}$ to 0.10 chains/nm$^{2}$. Thin sections are obtained by cryomicrotome at -140 $^{\circ}$C for TEM analysis. Without adding nanoparticles, bulk phase separation occurs for the PS-PB blend, although a few droplets of PS are found presumably due to the viscoelastic phase separation. When the grafting density is less than 0.05 chains/nm$^{2}$, the particles are found to partition between the PS-PB interface and the continuous PS phase. However, when the grafting density is greater than or equal to 0.05 chains/nm$^{2}$, the particles are found to locate only in the dispersed PS phase, and the size of the PS phases decreases with increasing grafting density. Phase inversion also occurs at 70 wt{\%} of PS when the grafting density is fixed at 0.10 chains/nm$^{2}$. [Preview Abstract] |
Tuesday, March 19, 2013 12:27PM - 12:39PM |
G34.00007: Application of Self-consistent Field Theory to Compressible Polymer Blends: $\chi $, interfacial tension, and anomaly Junhan Cho The self-consistent field (SCF) theory, which was first developed by Helfand, is generalized to compressible polymer blends in order to investigate pressure dependence of interfacial behavior for those systems. A statistical mechanical off-lattice equation-of-state model is incorporated with the formalism and proper SCF equations for saddle points are presented. Taking typical blends as our model system, the relationship between effective Flory-Huggins parameter and interfacial tension is considered on a temperature-pressure window. Anomaly in those physical properties regarding their pressure dependence is discussed. [Preview Abstract] |
Tuesday, March 19, 2013 12:39PM - 12:51PM |
G34.00008: Morphology and Rheology of the Phase-separating Polybutadiene /Polyisoprene Blend under Small Amplitude Oscillatory Shear Xia Dong, Fasheng Zou, Dujin Wang, Charles C. Han We are mainly focusing on the late stage of phase separation process where the two phases have reach their equilibrium compositions and the droplet dimension or interface area is the key factor in influencing the dynamic moduli. Two kinds of phase-separating structure evolutions of the PB/LPI blend have been investigated. For the near-critical and symmetric blend LPI50, the co-continuous phase-separating structures are observed and lead to a power law behavior of the dynamic storage modulus at low frequencies. With the growth of the co-continuous structure, the storage modulus at low frequency decreases dramatically. For the off-critical and asymmetric blend LPI70, the droplet/matrix two-phase structures appear and result in a rather complex elastic behavior at the mediate and low frequency region. It is observed that with the droplet size increases, the storage modulus at the mediate frequencies generally decreases while the storage modulus at the low frequencies usually increases. Besides, the platform and terminal moduli at a given frequency can be scalable with the phase separation time and the characteristic relaxation time and domain size of the droplets can be obtained by rheology. [Preview Abstract] |
Tuesday, March 19, 2013 12:51PM - 1:03PM |
G34.00009: Effective Mixing of UHMWPE with Polyethylene: Rheological, Mechanical and Crystallization Behavior of Novel Blends Made by Solid-State Shear Pulverization Mirian Diop, John Torkelson In comparison with conventional polyolefins, ultrahigh molecular weight polyethylene (UHMWPE) possesses outstanding mechanical properties, including impact strength, making it highly desirable for applications ranging from body armor to implants. Unfortunately, UHMWPE comes with a downside: an ultrahigh melt viscosity that renders common melt processes useless for making products from UHMWPE. Attempts to overcome this problem by blending UHMWPE with polyethylene (PE) by conventional melt mixing have been unsuccessful because of the enormous viscosity mismatch and have led to suspensions of UHMWPE particles within a PE matrix. Here, we show the utility of solid-state shear pulverization (SSSP) to effectively and intimately mix UHMWPE/PE blends. Oscillatory shear rheology of blends containing up to 20 wt{\%} UHMWPE shows both the major impact of the UHMWPE fraction in strongly modifying the low shear rate flow behavior and the very muted effect of that fraction on the high shear rate flow behavior. The latter effect indicates that such blends can be processed by melt extrusion and injection molding. Differential scanning calorimetry supports the presence of co-crystallization in these blends. Mechanical properties of these blends, including impact strength, will also be discussed. [Preview Abstract] |
Tuesday, March 19, 2013 1:03PM - 1:15PM |
G34.00010: Assessing the Strength Enhancement of Heterogeneous Networks of Miscible Polymer Blends Carl Giller, Mike Roland At the typical crosslink densities of elastomers, the failure properties vary inversely with mechanical stiffness, so that compounding entails a compromise between stiffness and strength. Our approach to circumvent this conventional limitation is by forming networks of two polymers that: (i) are thermodynamically miscible, whereby the chemical composition is uniform on the segmental level; and (ii) have markedly different reactivities for network formation. The resulting elastomer consists of one highly crosslinked component and one that is lightly or uncrosslinked. This disparity in crosslinking causes their respective contributions to the network mechanical response to differ diametrically. Earlier results showed some success with this approach for thermally crosslinked blends of 1,2-polybutadiene (PVE) and polyisoprene (PI), as well as ethylene-propylene copolymer (EPM) and ethylene-propylene-diene random terpolymer (EPDM), taking advantage of their differing reactivities to sulfur. In this work we demonstrate the miscibility of polyisobutylene (PIB) with butyl rubber (BR) (a copolymer of PIB and polyisoprene) and show that networks in which only the BR is crosslinked possess greater tensile strengths than neat BR over the same range of moduli. [Preview Abstract] |
Tuesday, March 19, 2013 1:15PM - 1:27PM |
G34.00011: Investigation of Flame Retardancy, Mechanical Properties, and Bicompatibility of Polystyrene Blends Liudi Zhang, Seongchan Pack, Miriam Rafailovich Our research focused on thermal, mechanical properties, and cytotoxicity of Polystyrene system. Brominated Polystyrene was incorporated to replace halogenated Flame Retardant in Polystyrene blends. We have previously shown that ditallow functionalized clays could become nearly universal class of compatiblizers [si-2006]. Here we show that a new type of surface with Resorcinol bis (biphenyl phosphate) (RDP) could achieve the same goal. We demonstrate the strong compatibilization on this highly immiscible system. Furthermore, we show that this system also works well, when a flame retardant Antimony Trioxide (AO) is added. Tensile test, dynamic mechanical analysis, and UL-94 flame test were applied to investigate this system. We found that the amount of AO used could be minimized by adding RDP clay, which could also increase some mechanical properties that Cloisite 20A clay couldn't. Besides, we evaluated the cytotoxicity of Cloiste 20A and RDP clay. These clays were tested both within PS blends and as a monolayer film. Langmuir-Blodgett trough and atomic force microscopy were used to make and check monolayer clay. Confocal laser scanning microscopy was used to assess cell morphology. The results showed RDP clay has potential for biomaterial applications. [Preview Abstract] |
Tuesday, March 19, 2013 1:27PM - 1:39PM |
G34.00012: Avalanches of dewetting holes in viscoelastic phase separation Changqian Yu, Sung Chul Bae, Steve Granick Textbook ideas fails regarding phase separation of polymer solutions, because of viscoelastic effects. Here with fluorescence microscopy we visualize in real time this process. Quasi two dimensional polymer solutions of polystyrene near the critical concentration are confined between non-wetting surfaces. Apart from a double phase separation induced by rapid hydrodynamic coarsening, we observe novel avalanched dewetting of solvent-enriched holes, not only in the polymer-enriched phase but also near the walls. Strikingly, this occurs at the late stage of the spinodal decomposition. These dewetting holes govern pattern evolution of the phase-separated polymer network. [Preview Abstract] |
Tuesday, March 19, 2013 1:39PM - 1:51PM |
G34.00013: Coalescence of Pickering emulsion droplets induced by electric-field Guo Chen, Peng Tan, Shuyu Chen, Jiping Huang, Weijia Wen, Lei Xu Combining high-speed photography with electric current measurement, we investigate the coalescence of Pickering emulsion droplets. Under high enough electric field, the originally-stable droplets coalesce via two distinct approaches: normal coalescence and abnormal coalescence. In the normal coalescence, a liquid bridge grows continuously and merges two droplets together, similar to the classical picture. In the abnormal coalescence, however, the bridge fails to grow indefinitely; instead it breaks up spontaneously due to the geometric constraint from particle shells. Such connecting-then-breaking cycles repeat multiple times, until a stable connection is established. In depth analysis indicates that the defect size in particle shells determines the exact merging behaviors: when the defects are larger than a critical size, normal coalescence will show up; while abnormal coalescence will appear for smaller defects. [Preview Abstract] |
Tuesday, March 19, 2013 1:51PM - 2:03PM |
G34.00014: Arrested of coalescence of emulsion droplets of arbitrary size Badel L. Mbanga, Christopher Burke, Donald W. Blair, Timothy J. Atherton With applications ranging from food products to cosmetics via targeted drug delivery systems, structured anisotropic colloids provide an efficient way to control the structure, properties and functions of emulsions. When two fluid emulsion droplets are brought in contact, a reduction of the interfacial tension drives their coalescence into a larger droplet of the same total volume and reduced exposed area. This coalescence can be partially or totally hindered by the presence of nano or micron-size particles that coat the interface as in Pickering emulsions. We investigate numerically the dependance of the mechanical stability of these arrested shapes on the particles size, their shape anisotropy, their polydispersity, their interaction with the solvent, and the particle-particle interactions. We discuss structural shape changes that can be induced by tuning the particles interactions after arrest occurs, and provide design parameters for the relevant experiments. [Preview Abstract] |
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