Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session L35: Sustainable Biopolymers for Enhanced ApplicationsFocus
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Sponsoring Units: DPOLY Chair: John Dutcher, Univ of Guelph Room: 507 |
Wednesday, March 4, 2020 8:00AM - 8:12AM |
L35.00001: Dendrimeric Morphology and Mechanical Modulus of Soft Phytoglycogen Nanoparticles Revealed by AFM Force Spectroscopy Benjamin Baylis, Erin Shelton, John Dutcher Phytoglycogen is a naturally occurring glucose polymer that is produced in the form of highly branched, compact nanoparticles by sweet corn. The deformability, unique hydration and inherent safety of the particles makes them desirable for applications in personal care, nutrition and biomedicine. We have used atomic force microscopy (AFM) force spectroscopy to measure the size, morphology, and stiffness of the phytoglycogen nanoparticles in both water and air. For measurements in water, we were successful in covalently bonding isolated phytoglycogen particles to gold using an intermediate layer of 4-mercaptophenylboronic acid. We used the Quantitative Imaging mode of our JPK AFM to collect high resolution force-distance maps of a large number of individual phytoglycogen particles, which revealed the inner dendrimeric morphology of the particles at the largest applied forces and allowed us to quantify the increase in the elastic modulus in going from the outer to the inner regions of the particles. We also observed large increases in the modulus for dry particles in air, quantifying the effect of hydration on the mechanical stiffness of the particles. |
Wednesday, March 4, 2020 8:12AM - 8:24AM |
L35.00002: Structure of Native and Hydrophobically Modified Phytoglycogen Nanoparticles Using Small Angle Neutron Scattering John H Atkinson, Jonathan Nickels, Michelle Michalski, Michael Grossutti, Adrian Schwan, John Katsaras, John Dutcher Phytoglycogen is a highly branched polymer of glucose produced as soft, compact nanoparticles by sweet corn. Properties such as softness, porosity and mechanical integrity, combined with nontoxicity and biodegradability, make phytoglycogen nanoparticles ideal for applications involving the human body. We describe small angle neutron scattering (SANS) measurements of native phytoglycogen and phytoglycogen that was hydrophobically modified using octenyl succinic anhydride (OSA) in both its hydrogenated (hOSA) and deuterated (dOSA) forms. The data for the native particles was well described by a core-coil model, in which the outer surfaces of the particles are covered by short chains. The data for highly modified hOSA-phytoglycogen was consistent with a “raspberry” model, in which the outermost chains decorated with hOSA collapsed to form “seeds” with a well-defined size and separation. For lower DS values for both hOSA and dOSA-phytoglycogen, the data was well described using a core-shell particle geometry in which the composition of the shell was consistent with measured DS values. The results of the present study offer new insights into the morphology of phytoglycogen nanoparticles and the physical nature of their modification with OSA. |
Wednesday, March 4, 2020 8:24AM - 8:36AM |
L35.00003: Hydration water structure, hydration forces, and mechanical properties of polysaccharide films Michael Grossutti, John Dutcher We have used ellipsometry at controlled relative humidity (RH) to measure the equilibrium swelling of ultrathin films of polysaccharides, including native and modified phytoglycogen nanoparticles as well as dextran and hyaluronic acid. At high humidities (RH > 70%), the RH-driven swelling of hydrophilic polymers can be described by exponentially decaying interstitial hydration forces. We have used two complementary approaches to analyse this high RH swelling regime to measure the length scale λ0 that characterizes exponentially decaying hydration forces and to quantify the associated bulk modulus Kp of the films. We further probe this swelling regime using attenuated total reflection infrared (ATR-IR) spectroscopy to investigate the hydrogen bond structure of the hydration water in the polysaccharide films. By combining ellipsometry and ATR-IR spectroscopy we find that the structuring of the hydration water hydrogen bond network in this regime correlates with both the hydration force decay length and film mechanical stiffness. These measurements provide insight into the relationship between the hydration water structure, hydration forces, and mechanical properties of polysaccharides, and suggest that a more ordered water hydrogen bond network leads to a smaller λ0 and larger Kp. |
Wednesday, March 4, 2020 8:36AM - 9:12AM |
L35.00004: Carbohydrate-Based Polymers and Nanomaterials for Advanced Technologies Invited Speaker: Maren Roman Carbohydrate-based polymers, termed polysaccharides, are ubiquitous in Nature. They perform a wide range of functions, including providing structural support in plant cell walls, generating swelling pressure in mammalian tissues, protecting microbes from dehydration and toxins, storing solar energy, and regulating binding events on cell surfaces. Owing to their diverse structures and properties, polysaccharides have found numerous industrial and medical applications. For example, they are used to increase the viscosity of food products and drilling fluids, stabilize emulsions, suspensions, and foams, form gels, prevent ice crystal formation, and protect wounds during healing. This presentation will showcase recent efforts at Virginia Tech toward the development of polysaccharide-based advanced technologies with biomedical and drug delivery applications. |
Wednesday, March 4, 2020 9:12AM - 9:24AM |
L35.00005: Structure-Property Mappings for Bio-Advantaged Polyhydroxyalkanoate (PHA)-based Polymers Karteek Bejagam, Carl N. Iverson, Babetta L. Marrone, Ghanshyam Pilania A steady increase in the consumption and rapid disposal of plastic products is currently imposing a stringent burden on the environment—translating into a range of severe problems from destruction of ecosystems to climate change. As a potential solution, biosynthetic and |
Wednesday, March 4, 2020 9:24AM - 9:36AM |
L35.00006: Enabling Circular Polymer Chemistry Through Computation Alexander Epstein, Peter Christensen, Trevor Seguin, brett helms, Kristin Persson Monomer-to-monomer recycling is a promising solution to the global plastic pollution crisis. However, most conventional plastics are difficult to depolymerize due to the large energy input required to degrade a carbon-carbon backbone. Instead, one can design polymers to incorporate bonds that are reversible in specific processes. This work demonstrates how quantum chemistry tools can be used to develop design rules for bonds that enable monomer-to-monomer recycling. Specifically, design rules were discovered for an exciting new polymer platform, called poly(dikeotenamine)s, which has been shown to display chemical circularity with >90% monomer yield. Design rules were developed from analysis of the simulated reaction pathway for the acid-catalyzed hydrolysis of the polymer with several heteroatom substitutions of the basic platform. Considering the ubiquity of the addition-elimination reaction in depolymerization processes, this analysis can inform design of a wide variety of monomer-to-monomer recycling techniques. |
Wednesday, March 4, 2020 9:36AM - 9:48AM |
L35.00007: Compression of Acid Hydrolyzed Phytoglycogen Nanoparticles at High Packing Densities Hurmiz Shamana, John Dutcher Phytoglycogen is a natural polysaccharide produced in the form of compact, 44 nm diameter nanoparticles in the kernels of sweet corn. Its highly branched, dendrimeric structure leads to interesting and useful properties that make the particles ideal as unique additives in personal care, nutrition and biomedical formulations. The properties of phytoglycogen nanoparticles can be altered through chemical modifications such as acid hydrolysis, which not only reduces their diameter but also produces significant changes to the interactions between particles in highly concentrated dispersions. At sufficiently small concentrations (C < 30% w/w), the acid hydrolyzed particles exhibit typical soft sphere behaviour characterized by an increase in the zero-shear viscosity with concentration, reaching a value that exceeds that of water by a factor of ~103 at C ~ 30% w/w. As the concentration is increased beyond 30% w/w (the concentration at which the particles begin to be compressed against one another), the dependence of zero-shear viscosity versus concentration data shows a pronounced kink, with increases beyond 30% w/w significantly more gradual. This result is consistent with a reduction in stiffness for acid hydrolyzed phytoglycogen nanoparticles. |
Wednesday, March 4, 2020 9:48AM - 10:00AM |
L35.00008: Tunable Yield Stress of Aqueous Dispersions of Hydrophobically-Modified Phytoglycogen Nanoparticles Carley Miki, Hurmiz Shamana, John Dutcher Phytoglycogen is a natural polysaccharide produced in the form of compact, 44 nm diameter nanoparticles in the kernels of sweet corn. Its highly branched, dendrimeric structure leads to interesting and useful properties that make the particles ideal as unique additives in personal care, nutrition and biomedical formulations. The properties of phytoglycogen can be readily altered through chemical modification. We consider a hydrophobic modification of phytoglycogen by covalently attaching charged, hydrophobic octenyl succinic anhydride (OSA) chains to the weakly charged, hydrophilic surface of phytoglycogen. When dispersed in water at moderate concentrations (C ~ 20% w/w), the OSA-modified particles form a shear-sensitive gel with a low shear viscosity that exceeds by a factor of ~106 that of native phytoglycogen dispersions of the same concentration. Furthermore, the dispersions exhibit a well-defined yield stress, as measured using different rheology techniques. The yield stress vanishes as the pH of the dispersions is reduced below the pKa of the acidic group of OSA, with the material transitioning from a shear-sensitive gel to a flowing liquid. This pH-sensitivity suggests new applications for OSA-modified phytoglycogen. |
Wednesday, March 4, 2020 10:00AM - 10:12AM |
L35.00009: Binding of Proteins to a Phytoglycogen-Functionalized Surface Plasmon Resonance Sensor Surface Kathleen Charlesworth, Nicholas van Heijst, Aidan Maxwell, Michael Grossutti, John Dutcher Phytoglycogen is a highly branched polymer of glucose produced as soft, compact nanoparticles by sweet corn. Properties such as softness, porosity and mechanical integrity, combined with nontoxicity and biodegradability, make phytoglycogen nanoparticles ideal for applications involving the human body. Many of these applications rely on the binding of small molecules onto phytoglycogen nanoparticles. Surface Plasmon Resonance (SPR) is a sensitive experimental technique, based on the resonant absorption of light within an ultrathin gold film, that can be used to measure the binding kinetics and affinities of small molecules. We have successfully created a stable phytoglycogen-functionalized SPR sensor surface, using 4-mercaptophenylboronic acid as a linker between the gold layer and phytoglycogen. This has allowed us to use SPR to measure the association constant between phytoglycogen and Concanavalin A (ConA) to be 2.87 ± 0.44 X 105 M-1 by fitting the data to the Langmuir adsorption model. By measuring the amide bands of ConA bound to phytoglycogen using infrared spectroscopy, we find that ConA maintains a large amount of its native beta-sheet content, suggesting that phytoglycogen helps to preserve its bioactivity. |
Wednesday, March 4, 2020 10:12AM - 10:24AM |
L35.00010: Plastic Resins for the Circular Economy: from Wind Turbines to Gummy Bear Candy and Beyond. John Dorgan, Bin Tan, Harshal Bambhania Plastics and composites have concerning sustainability metrics including high embedded energy and associated greenhouse gas emissions, low recyclability rates, and generation of microplastics pollution. Composites are notoriously difficult to recycle but are critical for wind turbine, lightweight vehicle, and other sustainable technologies. An economically viable, fully recyclable, composite resin is demonstrated; physical properties of composites produced from the reclaimed resin show true “turbine-to-turbine” recycling is possible. Various end-of-use options are established; regrinding produces short fiber moldable materials. Base catalyzed digestion produces poly(methyl methacrylate) or the superabsorbent poly(methacrylic acid). Distillation of the digestate produces methanol, water, and food grade potassium lactate; the resulting lactate has been incorporated into gummy bear candies. Judicious formulation of polymer resins enables complete circularity in low-embedded energy materials; exploitation of triggerable degradation provides varied and intriguing end-of-use recycling options. |
Wednesday, March 4, 2020 10:24AM - 11:00AM |
L35.00011: Performance-advantaged bioproducts from biomass Invited Speaker: Gregg Beckham Chemical intermediates accessible from selective processing of lignocellulose, namely carbohydrates from polysaccharides and aromatic oxygenated compounds from lignin, offer the potential for atom-efficient biological and catalytic transformations to new building blocks for biopolymers that are difficult to access from petroleum-derived, hydrocarbon intermediates. To that end, this talk will cover several new biopolymers via biological and catalytic transformations of carbohydrates and lignin-derived aromatic compounds that exhibit performance-advantaged properties relative to existing petroleum-based polymers. Performance-advantaged bioproducts, such as those described here, could potentially incentivize the development of a viable bioeconomy alongside biofuels production. |
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