Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session H6: Polymer Nanocomposites with Crystallizable Components and Fiber Reinforcement |
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Sponsoring Units: DPOLY Chair: Praveen Agarwal, Dow Chemical, Inc. Room: 265 |
Tuesday, March 14, 2017 2:30PM - 2:42PM |
H6.00001: EMPTY SLOT |
Tuesday, March 14, 2017 2:42PM - 2:54PM |
H6.00002: EMPTY SLOT |
Tuesday, March 14, 2017 2:54PM - 3:06PM |
H6.00003: EMPTY SLOT |
Tuesday, March 14, 2017 3:06PM - 3:18PM |
H6.00004: Crystallization behavior of nanocomposites based on poly(L-lactide) and layered double hydroxides -- Unbiased determination of the rigid amorphous phases due to the crystals and the nanofiller. Andreas Schoenhals, Jing Leng, Andreas Wurm, Christoph Schick Semicrystalline polymers have to be described by a three phase model consisting of a mobile amorphous (MAF), a crystalline (CF), and a rigid amorphous fraction (RAF). For nanocomposites based on a semicrystalline polymer the RAF is due to both the crystallites (RAF$_{\mathrm{crystal}})$ and the filler (RAF$_{\mathrm{filler}})$. In most cases a separation of both contributions is not possible without further assumptions. Here polymer nanocomposite based on poly(L-lactide) and layered double hydroxide nanofiller were prepared. Due to the low crystallization rate of PLA its crystallization can be suppressed by a high enough cooling rate, and the RAF is due only to the nanofiller. The MAF, CF, and RAF were estimated by Temperature Modulated DSC. For the first time CF, MAF, RAF$_{\mathrm{crystal}}$, and RAF$_{\mathrm{filler}}$ could be estimated without any assumption. Two different systems with a different degree of exfoliation were prepared and discussed in detail. [Preview Abstract] |
Tuesday, March 14, 2017 3:18PM - 3:30PM |
H6.00005: Crystallization in polymer nanocomposites Kyriakh Chrissopoulou, Helena Perivolari, Stefanos Leisch, Hellen Papananou, Spiros H. Anastasiadis Polymer crystallization is a very interesting topic since it is responsible for the final properties of the materials. On the other hand, addition of inorganic nanomaterials has been recently widely used to optimize polymer properties. In this work, the effect of the presence of surfaces and of the severe confinement on polymer morphology and crystallization are investigated in hydrophilic nanohybrids of poly(ethylene oxide) and silica nanoparticles of different sizes; hybrids with different ratios of the two kinds of nanoparticles were synthesized as well, to achieve the highest confinement. Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) were utilized to investigate the behavior and showed that the polymer chains that were able to crystallize showed a different crystalline behavior in the hybrids with lower Tm and lower crystallinity. Under severe confinement polymer crystallization was completely suppressed. Moreover, the crystallization kinetics was investigated with Isothermal Polarized Optical Microscopy (POM) and Isothermal Differential Scanning Calorimetry (DSC) showing different characteristics in the hybrids compared to that of the neat polymer depending on the silica content. Sponsored by the Greek GSRT (AENAO research project, Action KRIPIS) [Preview Abstract] |
Tuesday, March 14, 2017 3:30PM - 3:42PM |
H6.00006: Interfacial Effect on Confined Crystallization of Poly(ethylene oxide)/Silica Composites. Yunlan Su, Weiwei Zhao, Alejandro Müller, Xia Gao, Dujin Wang In this study, the interfacial confinement effect of silica (SiO$_{\mathrm{2}})$ nanoparticles on the crystallization behavior of poly(ethylene oxide) (PEO) composites has been systematically investigated considering the size and concentration of SiO$_{\mathrm{2}}$ as well as the molecular weight (Mw) of PEO in the composites. Only when Mw of PEO is higher than 1100 g/mol but lower than 35000 g/mol, do the composites with high silica loadings exhibit two crystallization peaks of PEO as determined by differential scanning calorimetry. The first peak at 0 --50 °C is assigned to the crystallization of bulk PEO, while the second at --20 to --30 °C is attributed to the crystallization of restricted PEO segments. Three-layer (amorphous, interfacial and bulk) model is proposed to interpret the confined crystallization of PEO/SiO$_{\mathrm{2}}$ composites, which is supported by the results of thermogravimetric analysis and solid-state $^{\mathrm{1}}$H nuclear magnetic resonance. In the amorphous layer, most PEO segments are directly adsorbed on SiO$_{\mathrm{2}}$ surface via hydrogen bonding, while for the interfacial layer, the conformation is closely connected with the polymer chain length, originating mainly from the inhomogeneous segment mobilities of adsorbed polymers along the direction perpendicular to the surface of silica. [Preview Abstract] |
Tuesday, March 14, 2017 3:42PM - 3:54PM |
H6.00007: On the Isothermal Crystallization of PVDF-BaTiO$_{\mathrm{3}}$ Nanocomposites Danielle Valdez, Dorina Chipara, James Hinthorne, Mircea Chipara Polyvinylidene fluoride (PVDF) is an unique polymer with ferroelectric, piezoelectric, and pyroelectric features. Barium titanate is a piezoelectric and ferroelectric ceramic. To enhance the ferroelectric and piezoelectric features, nanocomposites of polyvinylidene fluoride-barium titanate (PVDF-BaTiO$_{\mathrm{3}})$ have been obtained by dispersing BaTiO$_{\mathrm{3}}$ nanoparticles (from Nanostructured {\&} Amorphous Materials Inc.) within PVDF via melt mixing. To achieve an uniform distribution of nanoparticles, the melt mixing consisted of 3 segments (190 ~C and 60 rotations per minute (rpm) for 30 minutes, 210 ~ C and 80 rpm for 15 minutes, and 180 ~C and 6o rpm for 30 minutes. The mixing was set at a relatively high temperature as the melting temperature of PVDF is about 177 $^{\mathrm{o}}$C. Detailed isothermal Differential Scanning Calorimetry (DSC) data have been recorded in order to analyze the effect of BaTiO$_{\mathrm{3}}$ nanoparticles on the crystallization of the polymeric matrix. The DSC data are analyzed within the Avrami approach framework including newer developments (such as Ozawa, and the combined Avrami--Ozawa). An original mathematical framework is suggested. Supplementary Raman studies are discussed. [Preview Abstract] |
Tuesday, March 14, 2017 3:54PM - 4:06PM |
H6.00008: Synthesis and characterization of gold nanoparticles in a self-assembled ionic liquid polymer nanocomposite Harsha Magurudeniya, Bryan Ringstrand, Katherine Jungjohann, Millicent Firestone Incorporation of nanoparticles(NPs) into polymer matrices has attracted interest, offering a means to create multi-functional materials combining the attributes of polymers (flexibility, processability, mechanical durability) with the opto-electrical properties of NPs. Synthesis of a self-supporting, hierarchically structured Au NP-network polymer was accomplished \textit{via} a ``one-pot'' reaction employing a mesophase of AuCl$_{\mathrm{3}}$ and an imidazolium based-ionic liquid (IL) containing a acrylate group. \textit{In-situ} generation of NPs was achieved by reduction of Au$^{\mathrm{3+}}$which in turn yields concomitant initiation of the polymerization of the mesophase. FT-IR and thermal analysis confirmed acrylate cross-linking. X-ray scattering confirms preservation of the mesophase within the NP composite. TEM showed a distribution of the NPs within the composite of primarily non-spherical morphologies. The co-integration of a macromer, PEG diacrylate, served as a reducing agent for the Au and the amount incorporated into the mesophase allowed for manipulation of the swelling factor of the resultant nanocomposite in a ethanol, providing means to modulate the plasmonic resonance of the NPs. This methodology provides means for organizing NPs within the structured regions of the poly(IL) matrix. Such composites may be of interest for photonic/sensing applications. [Preview Abstract] |
Tuesday, March 14, 2017 4:06PM - 4:18PM |
H6.00009: Three dimensional visualization of voids in fiber reinforced composites using dual energy x-ray computed tomography Yasuhito Suzuki, Branden Kappes, Dylan Cousins, John Dorgan Fiber-reinforced composites (FRCs) become more and more common in many applications including automotives, wind turbine blades, and aerospace materials because of their superior mechanical properties. As the superior properties originate from the high strength and high modulus of fibers along the fiber direction, the material is highly anisotropic. Thus, the existence of voids may significantly affect the properties of FRCs. Although acoustic spectroscopy is used as a standard method to detects voids, it does not provide the detailed shape of voids. Here, we demonstrate that the use of dual energy x-ray computed tomography enables us to three dimensionally visualize voids. While conventional x-ray CT scan cannot differentiate air and polymer matrix due to their similar attenuation against x-rays, by using high energy and low energy X-ray, dual x-ray CT scan provides better separation between air and the matrix. Not only spherical voids in the matrix but also irregularly shaped voids because of the physical contact to fibers are visualized. This information can be utilized to optimize the processing conditions and sizing chemistry of the fibers. [Preview Abstract] |
Tuesday, March 14, 2017 4:18PM - 4:30PM |
H6.00010: Biomimetic Thermo-Responsive Polymer Nano-Composites. Joao Maia, Shaghayegh Khani, Elvis Cudjoe, Stuart Rowan Responsive polymer nano-composites have been fabricated with an inspiration from the defense mechanism of sea cucumbers, whose mechanical properties undergo a dramatic change upon exposure to an external stimulus. In order to make nano-composites that mimic this behavior, polymers with LCST behavior were grafted onto CNC nano-rods and subsequently incorporated into a viscoelastic matrix. The material was then found to show thermal stiffening properties upon exposure to a temperature above the LCST transition point and it was hypothesized that this transition is due to formation/breakage of a network that happens as a result of switching on/off the attractive interactions between the hydrophilic nano-rods. In the present study, we develop a mesoscale simulation model in order to study the same system and examine the validity of this hypothesis. Using Energy Conserving Dissipative Particle Dynamics we will monitor the structural changes in the system as the temperature is increased above the LCST point. Our results show that upon the collapse of the grafted chains in response to temperature, attractive interactions between the nano-rods are switched on and a network is formed. These findings are in agreement with the experimental results and confirm the proposed structural model. [Preview Abstract] |
Tuesday, March 14, 2017 4:30PM - 4:42PM |
H6.00011: Solvent Evaporation Induced Assembly in Binary Mixtures of Nanoparticles Shengfeng Cheng, Yanfei Tang, Gary Grest Large-scale molecular dynamics simulations are used to study the ordering induced by evaporating the solvent from a solution containing nanoparticles of two different sizes. A thick fluid film containing the solvent and nanoparticles in contact with the solvent vapor is first equilibrated. In this initial state there is an excess of the smaller nanoparticles near the liquid/vapor interface. The solvent evaporation process is initiated by removing the vapor at a controlled rate from a region far from the interface. Our results show that the ordering of nanoparticles is determined by the competition between the evaporation-induced movement of the liquid/vapor interface and the diffusion of the nanoparticles, which can be characterized by a dimensionless Peclet ($Pe$) number for each type of nanoparticles. When $Pe \gg 1$ for both nanoparticles, the accumulation of the smaller nanoparticles near the interface is enhanced during evaporation. However, when $Pe > 1$ for the larger nanoparticles while $Pe < 1$ for the smaller ones, the ordering exhibits the opposite trend with the larger nanoparticles accumulating near the interface. Our results reveal the critical role of the evaporation rate of the solvent on controlling the distribution of nanoparticles. [Preview Abstract] |
Tuesday, March 14, 2017 4:42PM - 4:54PM |
H6.00012: Electrospinning of Polymer Blend and Core Shell Polymeric Structures Oscar J. Guerrero, Javier Macossay Torres, Servando A. Garza, Dorina Chipara, Mircea Chipara Electrospinning is a relatively new technique to obtain polymer nanofibers. The availability of submicron fillers makes possible the production of one dimensional nanocomposites. The diameter of polymer nanofibers and related structures is ranging between from 10$^{\mathrm{-4}}$ m to 10$^{\mathrm{-9}}$ m. The production of polystyrene (PS) nanofibers, polyvinylidene fluoride (PVDF) nanofibers, PS-PVDF blend nanofibers and of PS-PVDF nanofibers with core-shell morphology is reported. The production of PS-PVDF blend nanofiber is possible as a common solvent dimethylacetamide has been used to obtain the polymeric solutions. The mats have been dried in an oven at 75 $^{\mathrm{o}}$C for 24 hours. Solvent removal was confirmed by TGA. The diameters and lengths distributions of the as obtained nanofibers have been determined by optical microscopy and scanning electron microscopy. Structural studies on the as obtained nanofibers were performed by Raman spectroscopy and Wide Angle X-Ray spectroscopy, and Differential Scanning Calorimetry. Attention will be focus on the conversion of the alpha phase PVDF (paraelectric) into the beta phase (ferroelectric). [Preview Abstract] |
Tuesday, March 14, 2017 4:54PM - 5:06PM |
H6.00013: Physical or Chemical Aging of PLGA Electrospun Fibers Related to its Sequence Distribution shanshan xu, chenhong wang, bin xiao, charles han Biodegradable aliphatic polyesters such as poly(lactic-co-glycolic acid) (PLGA) have been studied for decades and widely used in life sciences. However, the major problems encountered in time-controlled drug delivery, stress maintenance, aging and degradation of this kind of copolymer are lack of stability, which are relied on both molecular weight distribution and sequence distribution. Based on commonly used ring-opening polymerization, PLGA with different sequence distribution was synthesized by controlling the transesterfication. Detailed investigations on electrospun PLGA fibers were carried out to identify the major factor of physical aging or chemical aging. With stretched polymer chains in electrospun fibers, the physical aging could be obtained by both entropy relaxation and contraction of the fibrous membrane. Even under low humidity and low temperature far away from the glass transition temperature, the physical aging of polymer with broad sequence distribution can be intense. These previously unidentified properties can still be improved in regulated clinical application if approached from a different angle. [Preview Abstract] |
Tuesday, March 14, 2017 5:06PM - 5:18PM |
H6.00014: Biocompatible, Tactic PMMA Blend Fibers: Exploring Stereocomplex Formation Suying Wei, Tanusree Sarker, Jaishri Sharma, Yang Lu, Ashwinin Kucknoor, Lauren Washburn, Evan Wujcik Poly(methyl methacrylate), PMMA stereocomplex is among the most interesting synthetic helix that has demonstrated great potential in applications where controlled molecular environment helps facilitate the desired structure/functions. For example, stereocomplex thin film surface better supported the enzymatic activities than its individual counterpart. Molecular dynamics simulation indicated that local rigidity and functionalities of stereoregular polymers contributed to the varied surface tension. Electrospun fibers demonstrated stereocomplex formation from the tactic PMMA blend gel. Inspired by the promising studies in the literature, we prepared electrospun fibers of i- and s-PMMA blends at various ratios from different solvents and subsequently investigated their physicochemical and biological properties. Surface morphology and wettability were characterized by scanning electron microscopy and contact angle measurement respectively. The relative thermal stability was disclosed by thermal gravimetric analysis, while differential scanning calorimetry was used to study the phase behaviors of the blend fibers, and indication of stereocomplex formation was observed for one specific ratio which showed an extra melting peak. Furthermore, the biocompatibility and effects on cell adhesion and growth behavior were explored using a model mammalian HeLa cell line. [Preview Abstract] |
Tuesday, March 14, 2017 5:18PM - 5:30PM |
H6.00015: Monte Carlo Simulation of Amyloid Protofibril Formation Matthew S. Wilson, Guangjie Shi, Thomas W\"ust, David P. Landau, Friederike Schmid Aggregation processes of amyloid protofibrils are studied using the replica-exchange Wang-Landau (REWL)\footnote{T. Vogel, Y. W. Li, T. W\"ust, and D. P. Landau, Phys. Rev. E \textbf{90}, 023302 (2014).} algorithm to simulate multiple interacting model peptides. The H0P model\footnote{G. Shi, T. W\"ust, Y. W. Li, and D. P. Landau, J. Phys.: Conf. Ser. \textbf{640}, 012017 (2015).}, which adds an additional neutral polarity group to the classic hydrophobic-polar (HP) model\footnote{K. A. Dill, Biochemistry \textbf{24}, 1501 (1985); K. F. Lau and K. A. Dill, Macromolecules \textbf{22}, 3986 (1989).}, is used for simplicity and efficiency. Constituent peptides are modeled as short, intrinsically disordered H0P sequences, which do not form globular structures individually but self-assemble to form various aggregated structures. Using the parallelized sampling framework, the density of states is determined and the minimal energy state is identified. From thermodynamic quantities, the effects of peptide concentration are studied for the formation of protofibrillar structures. [Preview Abstract] |
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