Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session Z20: Polymer Blends |
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Sponsoring Units: DPOLY Chair: Mark Foster Room: 321 |
Friday, March 20, 2009 11:15AM - 11:27AM |
Z20.00001: Microemulsions in Asymmetric Polymer Blends Alisyn Nedoma, Megan Robertson, Nitash Balsara Microemulsions and lamellar phases have been observed in previous experiments wherein block copolymers are added to blends of immiscible homopolymers. To our knowledge, all of the previous studies are restricted to homopolymers of nearly identical chain lengths with critical volume fractions in the vicinity of 0.5 (symmetric systems). The present study concerns the formation of microemulsions and lamellar phases phases in blends of immiscible polymers with substantial differences in chain lengths and critical volume fractions far removed from 0.5 (asymmetric systems). The characteristics of the block copolymers that enable the creation of these phases will be discussed in the presentation. [Preview Abstract] |
Friday, March 20, 2009 11:27AM - 11:39AM |
Z20.00002: Nanostructured polymer blends by addition of gradient copolymer during melt mixing: Effects of copolymer sequence distribution on morphology and crystallization behavior Robert Sandoval, Jungki Kim, John Torkelson Nanostructured blends of polystyrene and poly(ethylene oxide) (PEO) are produced via the addition of styrene/methyl methacrylate (S/MMA) gradient copolymer during conventional melt mixing, introducing dipole-dipole interactions between PEO and MMA repeat units. Upon addition of S/MMA gradient copolymer, stable PEO domains with diameters of $\sim $ 100 nm are formed in optimized cases. This results in PEO domains homogenously crystallizing at $\sim $ -20 C, well below the crystallization temperature of bulk PEO ($\sim $ 50 C). Additionally, nanostructured blends annealed at room temperature for 40 days resulted in no melting behavior upon heating, showing that the nanoconfined PEO domains remain in a rubbery state at room temperature, while bulk PEO typically remains in a crystalline state. This demonstrates that the blend properties can be easily tuned by adjusting the copolymer characteristics. This study is the first to lead to nanostructured polymer blends from non-reactive, simple melt mixing of two homopolymers and a compatibilizer. [Preview Abstract] |
Friday, March 20, 2009 11:39AM - 11:51AM |
Z20.00003: A Morphological Study of Poly(Butylene Succinate)/Poly(Butylene Adipate) Blends with Different Blend Ratios and Crystallization Processes Jerold Schultz, Haijun Wang, Zhigua Gan, Shouke Yan Morphologies of blends of poly(butylene succinate) (PBS, m.p. 114\r{ }C) with poly(butylene adipate) (PBA, m.p. 60\r{ }C) varying in blend ratio and in crystallization temperature of the PBS component were studied using optical and atomic force microscopies. When PBS is crystallized at 75\r{ }C, subsequent PBA crystallization occurs only within PBS spherulites. When PBS is crystallized at 100\r{ }C, a portion of the PBA is rejected from the growing PBS. The morphological difference is also reflected in the time-dependence of the crystallization kinetics. The difference in behavior at these two temperatures reflects a large change in the diffusion length. Further, the location of PBA crystals within PBS spherulites depends on PBA concentration and on PBS crystallization temperature. Lower PBA concentrations lead to interlamellar segregation, while when PBA is the majority phase, interfibrillar crystallization crystallization dominates. Replace this text with your abstract body. [Preview Abstract] |
Friday, March 20, 2009 11:51AM - 12:03PM |
Z20.00004: Phase equilibria and crystallization in mixtures of azobenzene chromophore and triacrylate Garrett O'Malley, Kenneth Milam, Namil Kim, Thein Kyu A temperature versus composition phase diagram of azobenzene chromophore/triacrylate system was established by means of differential scanning calorimetry (DSC). The isotropic liquid (I) and crystal solid + liquid (Cr$_{1}$ + I$_{2})$ coexistence regions bound by liquidus and solidus lines were tested with the theoretical curves obtained by self consistently solving the combined free energies of Flory-Huggins (FH) theory for isotropic mixing and phase field (PF) theory for crystal solidification pertaining to the compositional order parameter (\textit{$\phi $}$_{1}$\textit{, $\phi $}$_{2})$ and the crystal order parameter (\textit{$\psi $}$_{1})$, respectively. With the aid of phase diagram, various phase morphologies were mapped through thermal quenching into various coexistence gaps. Azobenzene in the blend produced multiple crystal structures, including gigantic single crystals. Real time images demonstrating the nucleation and growth of the crystallization process were captures under polarized optical microscopy. The spatiotemporal growth of such single crystal has been elucidated theoretically using the time-dependant Ginzburg Landau (TDGL) dynamics. [Preview Abstract] |
Friday, March 20, 2009 12:03PM - 12:15PM |
Z20.00005: Miscibility Studies on Polymer Blends Modified with Phytochemicals Neelakandan Chandrasekaran, Thein Kyu The miscibility studies related to an amorphous poly(amide)/poly(vinyl pyrrolidone) [PA/PVP] blend with a crystalline phytochemical called ``Mangiferin'' is presented. Phytochemicals are plant derived chemicals which intrinsically possess multiple salubrious properties that are associated with prevention of diseases such as cancer, diabetes, cardiovascular disease, and hypertension. Incorporation of phytochemicals into polymers has shown to have very promising applications in wound healing, drug delivery, etc. The morphology of these materials is crucial to applications like hemodialysis, which is governed by thermodynamics and kinetics of the phase separation process. Hence, miscibility studies of PA/PVP blends with and without mangiferin have been carried out using dimethyl sulfoxide as a common solvent. Differential scanning calorimetry studies revealed that the binary PA/PVP blends were completely miscible at all compositions. However, the addition of mangiferin has led to liquid-liquid phase separation and liquid-solid phase transition in a composition dependent manner. Fourier transformed infrared spectroscopy was undertaken to determine specific interaction between the polymer constituents and the role of possible hydrogen bonding among three constituents will be discussed. [Preview Abstract] |
Friday, March 20, 2009 12:15PM - 12:27PM |
Z20.00006: Phase Separation Mechanism of Polybutadiene/Polyisoprene Blends Under Oscillatory Shear Flow Charles C. Han, Ruoyu Zhang, He Cheng, Xia Dong Viscoelastic polymer blends of polybutadiene (PB)/low vinyl content polyisoprene (LPI), with a lower critical solution temperature (LCST) has been studied under oscillatory flow conditions. The phase separation mechanism has been investigated with the consideration of the nucleation mechanism, spinodal fluctuations, and also the shear induced mixing. Frequency and temperature ramping rate dependence of the apparent binodal and spinodal points will be discussed. [Preview Abstract] |
Friday, March 20, 2009 12:27PM - 12:39PM |
Z20.00007: Impact of Deuterium Substitution on the Physical Properties of Polymer Melts and Blends Ronald White, Jane Lipson We examine the effects on blend properties when one of the polymeric components is deuterated. Here we use SANS-fitted model calculations to explore the underlying physical behavior, and relate our findings to subtle effects in molecular size and energetics. A special emphasis is given to the prediction and analysis of phase behavior for polymeric mixtures (e.g. liquid-liquid partial miscibility), including a comparison of phase diagrams for several related systems. We discuss effects such as pressure and molecular weight dependence and also include an analysis of calculations in which we probe the influence of key model parameters on blend miscibility. As with our earlier studies, the results featured here involve the application of a microscopically parameterized equation of state derived from an integral equation theory for lattice-based chain molecule fluids. [Preview Abstract] |
Friday, March 20, 2009 12:39PM - 12:51PM |
Z20.00008: Mapping Mechanical Properties and Glass Transition Temperature in Polymer Materials with sub-100 nm Resolution Maxim Nikiforov, Stephen Jesse, Sangah Gam, Russell Composto, Louis Germinario, Sergei Kalinin Thermomechanical properties at the nanoscale are extremely important for understanding fundamental as well as technological problems. To date, Local Thermal Analysis (LTA) provides information about glass transition and melting temperature with about 1-2 $\mu$m spatial resolution. We developed LTA technique based on Scanning Probe Microscopy that allows probing not only melting and glass transition temperatures, but also elastic and loss moduli on a 100 nanometer length scale. This universal method for quantitative thermomechanical analysis was used to study the kinetics of phase separation in PMMA:SAN system. The maps of mechanical properties as function of temperature were obtained with sub-100 nm resolution. The difference of mechanical properties for two materials was determined. [Preview Abstract] |
Friday, March 20, 2009 12:51PM - 1:03PM |
Z20.00009: Understanding Dynamics of Multicomponent Polymer Systems Using Homopolymer/Copolymer Blends Caleb Dyer, Dias Linton, Mark Dadmun Blending two polymers is a cost-effective method to produce new materials with tailored properties, although the effect of the presence of one component on the dynamics of the second component is not well understood. Recent studies on miscible polymer blends show that the local environment in a polymer blend has a critical impact on the dynamics of each component in the blend. To this end we have utilized neutron reflectivity (NR), quasi-elastic neutron scattering (QENS), and rheology to study the dynamics of a polystyrene-\textit{ran}-poly(methyl methacrylate) (PS-\textit{ran}-PMMA) copolymer in a PMMA matrix. The system consists of a miscible blend that is 90{\%} PMMA/10{\%} random copolymer. The copolymer composition varies from 60{\%} to 90{\%} MMA in the blend, effectively tuning the thermodynamic interactions in the system. We will present these results to provide insight into the role of thermodynamic interactions on the dynamics of this miscible polymer blend. [Preview Abstract] |
Friday, March 20, 2009 1:03PM - 1:15PM |
Z20.00010: Influence of polymer chain connectivity on local composition distribution in miscible polymer blends Dmitry Bedrov, Wenjuan Liu, Ralph Colby Molecular dynamics simulations using bead-necklace model have been utilized to investigate concentration distribution of local environments in model polymer blends. Distribution of effective composition around polymer segments has been investigated for different blend scenarios and bulk concentrations. Inter- and intramolecular contributions to the effective composition have been analyzed. Our analysis indicates that chains connectivity has a significant and nontrivial effect on distribution of effective composition around polymer segment. The results of this work are compared with assumptions of several theoretical models that commonly used to describe structural and dynamical correlations in miscible polymer blends. [Preview Abstract] |
Friday, March 20, 2009 1:15PM - 1:27PM |
Z20.00011: Origins of Deviations from the RPA in Polymer Blends: Simulations and Theory Jun Kyung Chung, David Morse We performed continuum Monte Carlo simulations of symmetric binary polymer blends to precisely quantify deviations from RPA predictions for composition fluctuations, including critical phenomena. This comparison is made possible by an unambiguous procedure for determining the self-consistent field (SCF) $\chi$ parameter by extrapolating thermodynamic perturbation theory to the limit of infinite chain length $N$. Corrections to the RPA are shown to be proportional to $N^{-1/2}$, and to be accurately predicted outside of the critical region by a renormalized one-loop theory. The difference between the apparent (i.e., measured) interaction parameter and the SCF value is positive (destabilizing) far from the spinodal ($\chi N \ll 1$) as the result of an $N$-dependence of the depth of the correlation hole in a melt. Near the critical point, this effect is almost exactly cancelled by the stabilizing effect of long-wavelength composition fluctuations, yielding a critical value of $\chi N$ quite close to the RPA prediction of $(\chi N) \simeq 2$. [Preview Abstract] |
Friday, March 20, 2009 1:27PM - 1:39PM |
Z20.00012: Two DSC Glass Transitions in Miscible Blends of Polyisoprene / Poly(4-\textit{tert}-butyl styrene) Junshu Zhao, Ye Sun, Lian Yu, Mark Ediger Conventional and temperature modulated differential scanning calorimetry experiments have been carried out on miscible blends of polyisoprene (PI) and poly(4-\textit{tert}-butyl styrene) (P4tBS) over a broad composition range. This system is characterized by an extraordinarily large component T$_{g}$ difference ($\sim $215 K) between the two homopolymers. Two distinct calorimetric T$_{g}$s were observed in blends with an intermediate composition range (25{\%}$\sim $50{\%} PI) by both conventional and temperature modulated DSC. Good agreement was found between the T$_{g }$values measured by the two methods. Fitting of the measured T$_{g}$s to the Lodge-McLeish model gives a $\phi _{self}$ of 0.62$\sim $0.64 for PI in this blend and 0.02$\sim $0.05 for P4tBS. The extracted $\phi _{self}$ for PI$_{ }$is comparable to reported values for PEO in blends with PMMA and is significantly larger than those reported for other PI blends with smaller component T$_{g}$ differences. This observation suggests the presence of a confinement effect in PI/P4tBS blends, which results in enhanced fast component dynamics below the effective T$_{g}$ of the slow component. [Preview Abstract] |
Friday, March 20, 2009 1:39PM - 1:51PM |
Z20.00013: Segmental dynamics in polymer blends: adapting the Long-Lequeux model. Gareth Royston, Paul Sotta, Didier Long In recent years several models have been proposed which attempt to describe the distribution of relaxation times observed in glass forming systems as they approach vitrification. We have adapted the Long-Lequeux model, initially proposed for van der Waals liquids, for application to polymer blends. Considering thermally induced density fluctuations, the glass transition is considered to be controlled by percolation of small domains of slow dynamics. Here we present a comparison of the model with experimental data including recently acquired data on miscible blends of poly(alpha-methylstyrene) and poly(cyclohexyl methacrylate). The model is shown to provide a good fit to the data over a range of conditions. [Preview Abstract] |
Friday, March 20, 2009 1:51PM - 2:03PM |
Z20.00014: The Viscoelastic Behavior of Polymer/Oligomer Blends Wei Zheng, Gregory McKenna, Sindee Simon The dynamics in athermal blends of poly($\alpha $-methyl styrene) (PaMS) and its short chain oligomer are investigated using rheometry and differential scanning calorimetry (DSC). Master curves for the dynamic shear responses, G' and G", are successfully constructed for both the pure materials and the blends, indicating the validity of the time-temperature superposition principle. The temperature dependence of the shift factor follows the WLF (Williams-Landel-Ferry) behavior over the temperature range studied, and for the blends, the dependence is dominated by the high mobility oligomer. The discrete relaxation spectra of the materials are calculated and are found to be broader for the blends than for the pure materials. A similar domination of the dynamics by the oligomer is observed in DSC enthalpy recovery studies and in the broadened glass transition from DSC. The ability to predict the dynamic responses of the blends from the responses of the neat materials is examined, and whether this prediction needs to incorporate the self-concentration idea as described in Colmenero's model will be discussed. [Preview Abstract] |
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