Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session L42: Focus Session: Renewable and Sustainable Polymers |
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Sponsoring Units: DPOLY Chair: Megan Robertson, University of Houston Room: 214B |
Wednesday, March 4, 2015 8:00AM - 8:36AM |
L42.00001: Ecobionanocomposites: Hierarchical supramolecular materials incorporating stereocomplexation Invited Speaker: John Dorgan Polylactides (PLAs) are a leading class of renewable plastics with several favorable sustainability metrics. However, for many applications basic PLA has insufficient properties. The combination of nanoscopic filler particles can be combined with the phenomena of stereocomplexation to create a new class of hierarchically structured materials. Recent progress on the development of these novel ecobionanocomposites is discussed. [Preview Abstract] |
Wednesday, March 4, 2015 8:36AM - 8:48AM |
L42.00002: Positive effect of biaxial stretching on the mechanical behavior of PLA-Talc nanocomposites Saadia Ouchiar, Gr\'egory Stoclet, Cyrille Cabaret, Vincent Gloaguen, Jean-Marc Lefebvre Poly (Lactic acid) (PLA), a biodegradable polyester issued from renewable resources, appears as a good candidate for the replacement of petrochemical-based materials due to its good combination of physical properties. However main drawbacks of PLA are its brittle behavior and its low thermal stability. One way to outclass these lacks consists in adding nanofillers into PLA. It is also recognized that the mechanical and barrier properties can be improved by biaxial drawing process. Consequently, this study deals with the enhancing effect of biaxial stretching on mechanical properties of Talc based PLA nanocomposites. The Talc content was varied between 0 to 30 wt{\%}. This high level of talc results in a decrease in material cost, in addition to the enhancement of various physical properties. A main result is that neat PLA, which initially exhibit a brittle behavior upon uniaxial stretching at room temperature, become ductile after being biaxially stretched under appropriate conditions. More surprising is that the same behavior is observed for the filled samples. The origin of these enhancing properties will be also discussed. [Preview Abstract] |
Wednesday, March 4, 2015 8:48AM - 9:00AM |
L42.00003: Manipulating Interactions in Cellulose Nanocrystal/Waterborne Epoxy Composites through Physical Mixing Meisha L. Shofner, Natalie M. Girouard, J. Carson Meredith, Gregory T. Schueneman The objective of this research is to more fully understand the relationships between component interactions and processing pathways in cellulose nanocrystal (CNC)/polymer composite materials. Specifically, wood-derived CNC/waterborne epoxy composites with CNC loadings up to 15 wt.{\%} were produced using two different protocols. Through relatively simple changes in processing, significant differences in CNC dispersion and composite physical properties were seen, and these changes were attributed to an association between the CNCs and the epoxy emulsion, similar in nature to colloidal haloing. Considering literature results available for CNC nanocomposites, as well as other types of polymer nanocomposites, these results support the assertion that the processing-structure-property relationships in such nanocomposites are diverse and can be used to design materials for a range of applications. Additionally, these results put into context the properties that can be expected in composites containing wood-based CNCs produced at a pilot scale facility as opposed to CNCs from other cellulose sources produced a few grams at a time, making these results relevant to the production of CNC-based composites at larger volumes. [Preview Abstract] |
Wednesday, March 4, 2015 9:00AM - 9:12AM |
L42.00004: Epoxy thermoset networks derived from vegetable oils and their blends Chang Ryu, Matthew Ravalli Epoxidized vegetable oils (EVOs), such as epoxidized soybean oil and linseed oils were prepared by the partial oxidation of the unsaturated double bonds in vegetable oils and used as monomers for preparing epoxy thermoset materials based on the cationic polymerization. These EVOs have been used to prepare epoxy thermosets of different network densities by cationic polymerization using onium salt catalyst. The crosslinked epoxy thermosets provide an ideal platform to study the structure-property-relationships of networked polymers. In particular, rheological studies on the epoxidized vegetable oil thermosets have been performed to measure the molecular weights between crosslinks (Mx) in the epoxy thermosets and to ultimately elucidate the role of functionality of epoxy groups in EVO on the mechanical and thermophysical properties of the epoxy thermoset materials. [Preview Abstract] |
Wednesday, March 4, 2015 9:12AM - 9:24AM |
L42.00005: Structure-Property Relationships in Thiol-Ene Networks Composed of Plant-Derived Phenolic Acids Guozhen Yang, Hiruy Tesefay, Megan Robertson Polymer films prepared through thiol-ene chemistry are attracting increasing attention due to their ease of preparation and superior physical properties. We are investigating the properties of thiol-ene films which contain plant-derived allylated phenolic acids as substitutes to traditional petroleum-derived ene-bearing components. Phenolic acids are readily available through a variety of plant sources and contain rigid aromatic rings which contribute mechanical strength to the resulting polymer films. In this study, the properties of polymer films containing four phenolic acids were explored: salicylic acid, 4-hydroxybenzoic acid, gentisic acid and gallic acid. The allylated phenolic acids vary in the relative number and placement of the allyl groups used in the preparation of the polymer films, which impacts the resulting crosslinking density, glass transition temperature, and mechanical behavior of the polymer films. We have developed relationships between the chemical structures of the phenolic acids and the thermal and mechanical behavior of the polymer films. [Preview Abstract] |
Wednesday, March 4, 2015 9:24AM - 9:36AM |
L42.00006: Polyester Vitrimers from Biosourced Lactones Jacob Brutman, Paula Delgado, Marc Hillmyer Crosslinked polymers with controllable healing characteristics have received significant attention over the last decade. However, there is still much to be developed with these materials in the sustainability arena. Herein, we studied the healing capabilities of crosslinked bioderived poly(lactones) through Lewis acid catalyzed transesterification reactions. Materials that use isodesmic reactions (e.g., transesterification) for healing are termed vitrimers and have been reported using a diverse range of chemistries. Our initial studies focused on the healing properties of amorphous star-shaped poly(($\pm$)-lactide) crosslinked with methylenediphenyl diisocyanate in the presence of stannous(II) octoate. These materials exhibited remarkably fast stress relaxation rates when compared with previously reported polyester-based vitrimers, and exhibited similar stress relaxation rates at temperatures 140 $^{\circ}$C lower. Furthermore, the materials were able to recover their original tensile strengths post-healing by heating the system at 140 $^{\circ}$C for only 30 min. These results will be described in this presentation, as well as our ongoing research efforts on utilizing renewable crosslinkers, a variety of Lewis acid catalysts, and other amorphous polyesters derived from substituted lactones. [Preview Abstract] |
Wednesday, March 4, 2015 9:36AM - 9:48AM |
L42.00007: Short-Range Correlation of Successive Helical Jump Motions of Poly(L-Lactic Acid) Chains as Revealed by Solid State NMR Wei Chen, Toshikazu Miyoshi Polylactide (i.e. Polylactic acid, PLA) is a renewable and biocompatible thermoplastic material, owning the largest market share among all biodegradable polymeric materials. Thus, understanding of microscopic structure and dynamics are definitively important subjects in further application. The helical jump motion in semi-crystalline polymers was proposed by Hoffmann et al to explain the $\alpha_{c}$ relaxation in the crystalline region. So far, solid-state NMR proved that several semi-crystalline polymers such as polyethylene, isotactic-polypropylene, etc, show large amplitude motions in the crystalline regions. Additionally, successive helical jump motions may lead to long-range chain diffusions. Actually, chain diffusions are determined in terms of combinations of the overall jump rates and coupling degree of the jumps. Thereby, elucidations of correlations of the individual helical jump motions are also scientifically and practically important in further understanding dynamic nature of the crystalline chains and the structural evolutions of polymer crystals. Here, we utilize enter-bands only detection of exchange (CODEX) and 2D exchange NMR to characterize molecular dynamics of the crystalline chains in PLLA $\alpha $ phase. Dynamic geometry, correlation time, and short-range correlation of individual chain dynamics of PLLA in the crystalline region are for the first time reported. [Preview Abstract] |
Wednesday, March 4, 2015 9:48AM - 10:00AM |
L42.00008: Rayleigh-Taylor Instability Analysis at Biobased Composite Interfaces Richard Wool, Xintian Su The Rayleigh-Taylor (RT) instability occurs when a light fluid (such as a gas) of density $\rho_{\mathrm{L}}$ forms an unstable interface with a heavy fluid of density $\rho_{\mathrm{H}}$ due to gravitational forces g in the heavy-over-light unstable configuration. The RT instability produces bubbles and spikes which grow with amplitude H $\sim$ [gkAt]$^{1/2}$ in the linear region (Hk\textless \textless 1) which evolves in a complex manner in the non-linear region (Hk\textgreater \textgreater 1). Here, the wavenumber k $=$ 2$\pi $/$\lambda $, $\lambda $ $=$ wavelength between instabilities, t $=$ time, and the Atwood number A $=$ ($\rho_{\mathrm{H}}$-$\rho_{\mathrm{L}})$/ ($\rho _{\mathrm{H}}+\rho_{\mathrm{L}})$. The RT instability is common in Inertial Confinement in Fusion reactors, Super Novas and for the first time reported here, in the interface of natural fibers with a liquid molding resin (soyoil) where the gas emitted from the natural fibers at T \textgreater 100 $^{\circ}$C explicitly forms and traps the bubbles and spike instabilities in the curing resin. The non-equilibrium spikes that form with A $=$ 0.999 (Hk\textgreater 1) are self-similar and behave as H $=$ H$_{\circ} + \beta \lambda $, where the initial instability height H$_{\circ} = $ 11.6 micron and $\beta = $ 0.6 for small spikes (\textless 50 $mu$m) and $\beta = $1.8 for larger spikes (\textgreater 50 $\mu$m). The RT spikes are used to tailor the permeability (\textit{breathability}) of the eco-leather like materials made with natural fibers and plant oils, where gas diffusion occurs by percolation along the natural fiber-spike interfaces. The eco-leather has substantially lower toxicity compared to natural leather, polyurethane and PVC (Funded by EPA). [Preview Abstract] |
Wednesday, March 4, 2015 10:00AM - 10:12AM |
L42.00009: Thermodynamic Interactions and Shear Alignment of Sustainable Triblock Copolymers Shu Wang, Megan Robertson, Sameer Vajjala Kesava, Enrique Gomez Fatty acid-derived acrylates, lauryl acrylate (LAc) and stearyl acrylate (SAc), were utilized in the preparation of poly(styrene-b-(LAc-co-SAc)-b-styrene) triblock copolymers. The thermodynamic interactions between polystryene and the polyacrylates were probed through rheology (determination of the order-disorder transition), cloud point measurements, and small angle neutron scattering. The Flory-Huggins interaction parameter was independent of the alkyl side-chain length when the side-chain contained greater than 10 carbon atoms. The thermal and mechanical properties of the triblock copolymers, which behave as thermoplastic elastomers, could be readily tuned by varying the acrylate composition, without changing the order-disorder transition temperature. Structural analysis revealed non-equilibrium spherical morphologies of the triblock copolymers, which transformed to highly-ordered cylindrical microstructures under large amplitude oscillatory shear at a temperature well below the order-disorder transition. [Preview Abstract] |
Wednesday, March 4, 2015 10:12AM - 10:24AM |
L42.00010: Structure and phase behavior of aqueous methylcellulose solutions John McAllister, Peter Schmidt, Timothy Lodge, Frank Bates Cellulose ethers (CE) constitute a multi-billion dollar industry, and have found end uses in a broad array of applications from construction materials, food products, personal care products, and pharmaceuticals for more than 80 years. Methylcellulose (MC, with the trade name METHOCEL\texttrademark ) is a CE in which there is a partial substitution of --OH groups with --OCH$_{\mathrm{3}}$ groups. This results in a polymer that is water-soluble at low temperatures, and aqueous solutions of MC display gelation and phase separation at higher temperatures. The nature of MC gelation has been debated for many years, and this project has made significant advances in the understanding of the solution properties of CEs. We have characterized a fibrillar structure of MC gels by cryogenic transmission electron microscopy (cryo-TEM) and small angle neutron scattering (SANS). Using light scattering, turbidity measurements, and dynamic mechanical spectroscopy (DMS) we report that MC microphase separates by nucleation and growth of fibril aggregates, and is a different process from LCST phase separation. [Preview Abstract] |
Wednesday, March 4, 2015 10:24AM - 11:00AM |
L42.00011: Water in Renewable Polymers: Nonequilibrium Thermodynamics Invited Speaker: Yossef Elabd The design of polymers derived from sustainable resources (renewable polymers) as replacements to nonrenewable plastics for various applications will require an accurate assessment and fundamental understanding of the dynamics water sorption in glassy polymers. In this work, water sorption and diffusion in a number of glassy polymers (including the renewable polymer poly(lactide)) were measured using gravimetric and spectroscopic techniques. Non-Fickian diffusion was observed in all polymers studied, which was indicated by rapid, initial water uptake (driven by a concentration gradient), followed by continuous, gradual uptake of water at later experimental times (driven by slow polymer relaxation). Additionally, water sorption in these glassy polymers was predicted using two nonequilibrium thermodynamic models, where excellent agreement between the model prediction and experimental data was achieved for both models. Furthermore, contrasting physical pictures of water clustering were obtained between the Zimm-Lundberg theory and direct measurements. [Preview Abstract] |
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