Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session Z40: Semi Crystalline Polymers: Morphology and Electronics |
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Sponsoring Units: DPOLY Chair: Robert Hoy, Yale University Room: A122/123 |
Friday, March 25, 2011 11:15AM - 11:27AM |
Z40.00001: Structure Evolution of Propylene-1-Butylene Random Copolymer under Uniaxial Stretching: from Unit Cells to Lamellae Yimin Mao, Christian Burger, Xiaowei Li, Benjamin Hsiao Crystallization changes of propylene-1-butylene (P-H) random copolymer with low butylene content (5.7 mol\%) under uniaxial tensile deformation at high temperature (100 $^{\circ}$C) was investigated using time-resolved wide- and small-angle X-ray scattering (WAXS/SAXS) techniques. Structure and preferred orientation at length scales of crystal unit cell and lamellae were investigated explicitly using 2D whole pattern analysis. $\gamma$-phase was found to be the dominant initial modification which was transformed into $\alpha$-phase during stretching, forming more stable parallel packed polymer chains in the unit cell. 2D WAXS analysis enabled us to identify three orientation modes from different crystal forms, i.e., $\gamma$-phase with tilted cross-$\beta$ configuration, $\alpha$-phase with parallel chain packing and \emph{a}-axis orientation of $\alpha$-form crystals in daughter lamellae. 2D SAXS analysis based on stacking model enabled us to understand the development of the four-point pattern under deformation. [Preview Abstract] |
Friday, March 25, 2011 11:27AM - 11:39AM |
Z40.00002: An In-Situ X-ray Scattering Study during Uniaxial Stretching of Ionic liquid/Ultra-High Molecular Weight Polyethylene Blend Xiaowei Li, Yimin Mao, Hongyang Ma, Benjamin S. Hsiao The 1-docosanyl-3-methylimidazolium bromide ionic liquid (IL) was incorporated into ultra-high molecular weight polyethylene (UHMWPE) to form IL/UHWMPE blend by solution mixing. The structure evolution of this blend system during uniaxial stretching was followed by in-situ synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. During deformation at room temperature, the elongation-to-break ratio of the IL/UHMWPE blend increased by 2 - 3 times compared with pure UHMWPE sample, where the blend did not lose the tensile strength. Deformation-induced phase transformation from orthorhombic to monoclinic phase was observed in both blend and neat UHMWPE. During deformation at high temperature (120 $^{\circ}$C), no phase transformation was observed in both samples. However, the blend showed better toughness, higher crystal orientation, and tilted lamellar structure at high strains. [Preview Abstract] |
Friday, March 25, 2011 11:39AM - 11:51AM |
Z40.00003: Microscopic kinetic model for polymer crystal growth Wenbing Hu Linear crystal growth rates characterize the net result of competition between growth and melting at the liquid-solid interfaces. The rate equation for polymer crystal growth can be derived with a barrier term for crystal growth and with a driving force term of excess lamellar thickness, provided that growth and melting share the same rate-determining steps at the growth front. Such an ansatz can be verified by the kinetic symmetry between growth and melting around the melting point of lamellar crystals, as made in our recent dynamic Monte Carlo simulations. The profile of the growth/melting front appears as wedge-shaped, with the free energy barrier for intramolecular secondary crystal nucleation at its top, and with the driving force gained via instant thickening at its bottom. Such a scenario explains unique phenomena on polymer crystal growth, such as chain folding, regime transitions, molecular segregation of polydisperse polymers, self-poisoning with integer-number chain-folding of short chains, and colligative growth rates of binary mixtures of two chain lengths. [Preview Abstract] |
Friday, March 25, 2011 11:51AM - 12:03PM |
Z40.00004: Polyethylene crystallization in compatibilized polyethylene/polyamide 6 blends Simona Ceccia, Katerina Hynstova, Alexandra Fabre, Lise Trouillet-Fonti, Didier Long, Paul Sotta Blends of semicrystalline polymers can exhibit much better properties than each of the pure polymers regarding e.g. impact/modulus compromise. Controlling the crystallization mechanisms (nucleation, kinetics) is a key factor to obtain the desired morphologies which lead to these unique properties. We have studied the crystallization of polyethylene (PE) in blends of PE and polyamide 6 (PA) compatibilized by PE functionalized with maleic anhydride (PE-g-MA, 1 wt{\%} MA) obtained by reactive blending. Samples with different amounts of PA6 (0-60 {\%}vol) have been investigated by polarized optical microscopy and Differential Scanning Calorimetry. The samples were heated at a temperature above the melting temperature of PE and below the melting temperature of PA, and then cooled at the selected crystallization temperature. We describe how the crystallization kinetics is modified by the presence of PA and MA. [Preview Abstract] |
Friday, March 25, 2011 12:03PM - 12:15PM |
Z40.00005: Kinetic Partitioning of 1-Butene Defect in Random Propylene 1-Butene Copolymers by Time-Resolved FTIR Carolina Ruiz-Orta, Rufina G. Alamo Two different types of regularity bands are identified in a time-resolved FTIR crystallization of a series of random isotactic propylene 1-butene copolymers with a concentration of 1-butene from 2 to 19 mol{\%}. The first type are bands associated with 31 helices of isotactic sequences of different n length (n, number of monomer units). The second are regularity bands at 830, 920, 1010 and 1240 cm-1 associated with continuous sequences of the chain that include the 1-butene comonomer. Conformational changes during the isothermal crystallization process were monitored with these regularity bands. The variation of the intensity of regularity band at 920 cm-1 with crystallinity content and a shift of the 841 cm-1 (n = 12) at lower frequencies correlate with the content of comonomer included in the crystal. Changes in frequency of the n = 12 band with varying crystallization temperature (Tc), and with crystallization time at a fixed Tc are associated with the kinetic partitioning of the comonomer units, that was quantified with data obtained from 13C NMR. The frequency shift is absent in copolymers with co-units that are excluded from the crystalline regions, such as the 1-octene comonomer. [Preview Abstract] |
Friday, March 25, 2011 12:15PM - 12:27PM |
Z40.00006: Homogeneous bulk, surface, and edge nucleation in crystalline nanodroplets Jessica L. Carvalho, Kari Dalnoki-Veress We present a study on the homogeneous nucleation of dewetted poly(ethylene oxide) droplets on a substrate that is itself crystallisable. While the chemical properties of the substrate prepared in either the amorphous or crystalline state are identical, the surface landscape varies widely. We observe a large difference in the substrate's nucleating ability depending on how it is prepared. Furthermore, the scaling dependence of the nucleation rate on the size of the droplets depends on the substrate surface properties. The birth of the crystalline state can be directed to originate predominantly within the bulk, at the substrate surface or at the droplet's edge depending on how we tune the substrate. \\[4pt] J.L. Carvalho and K. Dalnoki-Veress, Phys. Rev. Lett in press, 2010. [Preview Abstract] |
Friday, March 25, 2011 12:27PM - 12:39PM |
Z40.00007: Molecular simulation of homogeneous crystal nucleation of n-alkane melts Peng Yi, Gregory Rutledge One of the most important phenomena in molecular systems is homogeneous nucleation of the crystal phase from a melt. This phenomenon is particularly interesting for chain molecules due to their strong anisotropy and their conformational flexibility. In this work we report the results of molecular simulations of homogeneous crystal nucleation of n-eicosane (C20) from the melt. A realistic united atom force field was employed. The crystal phase and melting behavior were first determined by ramping temperature in a set of MD simulations. The nucleation trajectory was then sampled using MD simulations at about 20{\%} supercooling; and the nucleation free energy was sampled using Monte Carlo umbrella sampling method for three temperatures, ranging from 10{\%} to 20{\%} supercooling. A first-passage time technique was used to determine the critical nucleus and the nucleation rate. Detailed examination of the simulations reveals the critical nucleus to be a bundle of stretched segments about 8 CH2 groups long, organized into a cylindrical shape. The remaining CH2 groups form a disordered interfacial layer. By fitting the nucleation free energy curve to the cylindrical nucleus model, the crystal-melt interfacial free energies are calculated to be about 10 mJ/m2 for the side surface and 4 mJ/m2 for the end surface. We also discussed the effect of using different nucleus definitions [Preview Abstract] |
Friday, March 25, 2011 12:39PM - 12:51PM |
Z40.00008: Hierarchal Ordered Structures in Hybrid Functional Supramolecules and Macromolecules Stephen Cheng, Wen-Bin Zhang, Chien-Lung Wang, Xinfei Yu, Yiwen Li, Xuehui Dong, Ryan Van Horn To create new functional materials for advanced technologies, control over their hierarchical structure and order is vital for obtaining the desired properties. We utilized and functionalized fullerene (C$_{60})$ and polyhedral oligomeric silsesquioxane (POSS), and assembed both of these particles with polymers to form those hierarchical structures. In order to do so, we have developed a novel way of attaching C$_{60}$ and POSS onto other organic materials in a highly efficient and controlled manner via ``click'' chemistry. The structure of this assembly along with the resulting ordered structures were analyzed to determine their structure-property relationships. Examples are materials of POSS-[60]Fullerenoacetate conjugate crystals, giant surfactant of polystyrene-(carboxylic acid-functionalized polyhedral oligomeric silsesquioxane) amphiphile and porphyrin-C$_{60}$ hybrids for intra- and inter-columnar in supramolecular double cable structures. [Preview Abstract] |
Friday, March 25, 2011 12:51PM - 1:03PM |
Z40.00009: Nanoconfined Ferroelectricity in Polymers Lei Zhu, Fangxiao Guan, Jing Wang, Qing Wang In this presentation, a low loss polystyrene (PS) was grafted as side chains onto the P(VDF-CTFE) main chain. After PVDF crystallization, dielectric PS side chains were segregated to the crystalline-amorphous interface, forming a finite confinement layer for ferroelectric PVDF crystals. We speculated that less space charge was induced during electric poling because of the nanoscale confinement effect. Consequently, a fast discharge speed, relatively high energy density, and low losses were achieved. [Preview Abstract] |
Friday, March 25, 2011 1:03PM - 1:15PM |
Z40.00010: Quantifying the rapid dynamics of polyelectrochromic switching in polymer acid-doped polyaniline Jacob Tarver, Yueh-Lin Loo Films cast from particles comprising polyaniline template synthesized on poly(2-acrylamido-2-methyl-1-propanesulfonic acid) exhibit polyelectrochromism and possess superior switching times ($<$10 s) and enhanced stability relative to other polymer acid-doped polyaniline systems. Solvent annealing in dichloroacetic acid induces polymer chain relaxation and further improves the speed ($\sim $1 s) and stability of electrochromic cycling. Electrochromic responses before and after solvent annealing can be described by Avrami kinetics that capture the influence of the film's mesoscale structural development and reveal variations in the dimensionality of reaction fronts when switching between the insulating and conducting states. Transitions from the conductive state are best fit by an Avrami exponent of 1.5 and are consistent with a reaction homogenously initiated throughout the film. Transitions to the conductive state require fits with exponents $\ge $2, suggesting nucleation and auto-accelerated propagation of conductive pathways away from the film/electrode interface in a manner analogous to polymer crystallization. [Preview Abstract] |
Friday, March 25, 2011 1:15PM - 1:27PM |
Z40.00011: Enhanced RF Heating of Poly(N-Isopropylacrylamide) Gels by Utilization of Multiferroic Nanoparticles Ezekiel Walker, Yukikuni Akishige, James Roberst, Tong Cai, Zhibing Hu, Arup Neogi Poly(N-Isoproylacrylamide) polymer hydrogels possess the special property of a discontinuous volumetric phase transition. This phase transition can be induced by external stimuli such as temperature, light, electric or magnetic fields, PH, and others. Of great interest is the functionalization of the gels to external stimuli for faster and more uniform spatial response. An efficient route to functionalization, specifically for termperature and light, is to utilize nanoparticles with EM resonances in the polymer network. The nanoparticles would be distributed throughout the gels, and an EM source resonant with the nanoparticle-gel structure would be used to induce a hysteresis-like effect to heat the gels, thereby, electromagnetically controlling the phase of the gel. KF-BaTiO$_{3}$ and BiFeO$_{3}$ are two sets of promising multiferroic nanoparticles that have exhibited resonances in the GHz region. Here, we present our findings for the functionalization and enhancement of the gels for radio-frequency light using KF-BaTiO$_{3}$ and BiFeO$_{3}$. [Preview Abstract] |
Friday, March 25, 2011 1:27PM - 1:39PM |
Z40.00012: Manipulating functional properties at the interface of composite organic semiconductors Panagiotis Maniadis, Turab Lookman, Avadh Saxena, Daryl Smith The formation of interfaces between different conjugated polymers is very important for the function of organic solar cells and other organic semiconductor devices. We propose a mechanism to control the properties of these interfaces with the addition of specially designed macro-molecules, with functional units. We develop the framework, using self consistent field theory (SCF), to study the concentration and the correlation function related to these functional units. When the functional units include a dipole moment, the average dipole moment and the standard deviation is expressed as a function of the SCF propagators. For electrostatic dipoles we also calculate the electric field difference created by the dipoles, as well as the charge distribution. [Preview Abstract] |
Friday, March 25, 2011 1:39PM - 1:51PM |
Z40.00013: The Role of Exciton Dynamics in Photorefractivity in Organic Semiconductors Mohammad Samiullah A theory of the photorefractive effect in organic photorefractive materials based on formation, diffusion and dissociation of excitons in organic polymer semiconductors will be presented. A comparison with experimental results shows that the exciton dynamics plays an important role in the creation of the space charge field, and should be considered when selecting candidates for photorefractivity in organic systems. [Preview Abstract] |
Friday, March 25, 2011 1:51PM - 2:03PM |
Z40.00014: Smart lens made of dielectric elastomer: simulation study Hong Tang Electroactive Polymers (EAPs) are polymers that exhibit a change in size or shape when stimulated by an electric field. The common applications of this type of material are in actuators and sensors. A typical characteristic property of an EAP is that they will undergo a large amount of deformation while sustaining large forces. It has been demonstrated that EAPs can exhibit a strain from 10{\%} to 300{\%}. A dielectric elastomer (DEA) is a compliant capacitor, where a passive elastomer film is sandwiched between two compliant electrodes. When a voltage is applied, the electrostatic pressure arising from the Coulomb forces acting between the electrodes, therefore the electrodes squeeze the elastomer film. Based on the finite element analysis, we simulated the deformation of a polymer lens made of transparent dielectric elastomer materials under an application of electric field, which is provided by the transparent thin metal layers coated on the upper and lower surfaces of the lens. The focus of the lens can be adjusted by the applied electric field strength. By designing the electrode configuration on the lens surfaces, one can achieve both the positive and negative adjustment for the focus length. [Preview Abstract] |
Friday, March 25, 2011 2:03PM - 2:15PM |
Z40.00015: ABSTRACT WITHDRAWN |
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