Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session A08: Sustainable Polymers: Fundamental Properties, Applications, and Design for End-of-LifeFocus Live
|
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Megan Robertson, University of Houston; Joe Stanzione, Rowan University |
Monday, March 15, 2021 8:00AM - 8:12AM Live |
A08.00001: Engineering Lignin-derived Polymers to be Recyclable by Design. James Sternberg, Srikanth Pilla The environmental crisis caused by the modern accumulation of plastic waste has driven many to search for a circular lifecycle for commodity plastics. In this presentation, we report the results of a study aimed at chemically recycling lignin-derived non-diisocyanate polyurethanes and track the structural alteration that occurs to recycled precursors. Starting from a protocol developed in our lab for non-isocyanate polyurethane foams, a hydrolytic chemical recycling technique is used to revert waste polymers back to their precursors: lignin and a bio-derived curing agent. In addition, through the use of vulnerable "molecular zippers" throughout the polymer structure, native structural features of lignin can be regenerated during chemical recycling. By minimizing the structural alteration to lignin, the hydroxyl content can be maintained and utilized for a subsequent generation of polymer synthesis. A unique window is opened toward understanding how lignin can be used in the rational design of polymer structures specifically engineered to undergo chemical recycling at their end of life. |
Monday, March 15, 2021 8:12AM - 8:24AM Live |
A08.00002: Bio-based Reprocessable Polyhydroxyurethane Networks: Full Recovery of Cross-link Density with Three Concurrent Dynamic Chemistries Sumeng Hu, Xi Chen, John Torkelson Despite significant past efforts to improve the renewability and recyclability of non-isocyanate polyurethane (NIPU) networks, no previous study has attempted to achieve reprocessability of bio-based polyhydroxyurethane (PHU) networks. We have synthesized renewable, dynamic PHU networks by reacting bio-derived cyclic carbonates, carbonated soybean oil (CSBO) and sorbitol ether carbonate (SEC), with synthetic or bio-based diamines. With relatively mild reprocessing conditions, CSBO-based PHU networks exhibit complete recovery of cross-link density and associated properties after multiple melt-state reprocessing steps. Besides the presence of reversible cyclic carbonate aminolysis and transcarbamoylation exchange reactions, CSBO-based networks were shown via a model reaction to undergo a third dynamic chemistry: transesterification exchange reaction. In contrast to the excellent property recovery achieved by CSBO-based PHU networks, as a result of disadvantageous monomer molecular design, SEC-based networks exhibit poor reprocessability. This work reveals the effect of monomer structure on the reprocessability of dynamic polymer networks and highlights the effectiveness of CSBO to serve as a precursor of robust, sustainable NIPU networks with excellent reprocessability. |
Monday, March 15, 2021 8:24AM - 8:36AM Live |
A08.00003: Non-isocyanate Polyurethanes for Thermoplastics and Foams: Opportunities for Green Chemistry and Sustainability Timothy Long, Jose Sintas, Josh Wolfgang The interest for monomers with reduced toxicity and broader applications is driven in part by the green chemistry revolution. As synthetic chemistries continue to develop, the desire to infuse sustainability into research catalyzes the development of new pathways for polymer synthesis. One such example is the utilization of carbonyldiimidazole (CDI) to drive the isocyanate-free synthesis of polyurethane foams and thermoplastics in a solvent-free, catalyst-free process. The versatile reactivity of CDI enables new families of bis-carbonylimidazole (BCI) monomers, which readily react with amines to form linear and crosslinked polyurethanes. This new CDI chemistry presents the potential for new structure-property relationships for high performance applications and safer engineering platforms for manufacturing while simultaneously implementing green chemistry. The elimination of petroleum-derived solvent, while simultaneously increasing the versatility of the final polyurethane harmonizes BCI monomers with green chemistry. Current research focuses on understanding the fundamental structure-property relationships in the isocyanate-free CDI system with the goal of creating a more circular use for polyurethanes globally. |
Monday, March 15, 2021 8:36AM - 9:12AM Live |
A08.00004: Dynamic covalent polymer networks and network composites: Excellent cross-link density recovery and elevated-temperature creep resistance after multiple recycling steps Invited Speaker: John Torkelson Conventional crosslinked polymers and their composites cannot be melt-reprocessed into high-value products because permanent crosslinks prevent melt flow. Examples include spent rubber tires and polyurethane (PU) foam, with major economic and sustainability losses resulting from the inability to upcycle these spent materials or have them become a part of the circular economy. Although dynamic covalent networks (DCPNs) and their composites allow for melt-state reprocessability, an "Achilles heel" has been identified with DCPNs that undergo exchange reactions, also called vitrimers: "For applications in typical vitrimer processing of rigid networks, the creep is highly undesirable in most application where elastomers are typically used." (Denissen et al., Chem. Sci. 2016) For example, significant creep in tires made with dynamic crosslinks would eliminate any possible commercial application. We show that elevated-temperature (T) creep can be strongly suppressed or arrested in both addition-type and step-growth-type DCPNs and their composites, including biobased and synthetic, by use of certain chemistries where the dynamic nature is entirely reversible (dissociative) or both reversible and exchange (associative). Alkoxyamine amine and dialkylamino disulfide reversible dynamic chemistries yield DCPNs and DCPN composites that exhibit excellent recovery of crosslink density after reprocessing at 130-160 degrees C and arrest of creep at 80 degrees C. PU networks their variants, e.g., polyhydroxyurethane and polythiourethane, have combined associative and dissociative dynamic chemistry and can exhibit excellent post-reprocessing crosslink density recovery, elevated-T creep resistance, and potential for monomer recovery. We will explain the underlying causes for the elevated-T creep resistance. These achievements of crosslink density recovery after reprocessing and elevated-T creep resistance are important in moving DCPNs from the research lab to commercial application. |
Monday, March 15, 2021 9:12AM - 9:24AM Live |
A08.00005: The Effect of Processing on Crystallization in Mixed Polyolefins Derek E Huang, Anthony Kotula, Kalman Migler The production of useful products from mixed waste-stream polyolefins requires processing strategies that account for the complex crystallization kinetics of such immiscible blends. While the topics of polymer crystallization and blending are both well-established in the literature, there is considerably less knowledge of how the fundamental parameters that govern polymer blending affect crystallization. Here we utilize the rheo-Raman-microscope and phase contrast microscopy under shear to explore the model immiscible system of isotactic polypropylene and high density polyethylene. We find a strong dependence of domain size, shear rate and cooling rate on crystallization kinetics and its associated rheology. These results underscore the complex multi-variate space that must be understood in order to control the behavior of mixed waste-stream materials in processing operations. |
Monday, March 15, 2021 9:24AM - 9:36AM Live |
A08.00006: Interplay Between Electrostatic and Hydrophobic Interactions in Aqueous Dispersions of OSA-Modified Phytoglycogen Nanoparticles Carley Miki, Hurmiz Shamana, John Dutcher Phytoglycogen is a natural polysaccharide produced in sweet corn in the form of compact, 44 nm diameter nanoparticles. Its highly branched, dendritic 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 altered through chemical modification. We consider the covalent attachment of charged, hydrophobic octenyl succinic anhydride (OSA) chains to the weakly charged, hydrophilic surface of phytoglycogen.1 When dispersed in water, the OSA-modified particles develop solid-like rheological behaviour with increasing concentration and exhibit a well-defined yield stress at a concentration much smaller than that for native phytoglycogen dispersions. 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 to ultimately precipitating out of solution at the lowest pH values. This result highlights the unique interplay between the electrostatic and hydrophobic interactions of the particles and suggests new applications for OSA-modified phytoglycogen. |
Monday, March 15, 2021 9:36AM - 9:48AM Live |
A08.00007: Crazing Mechanism and Physical Aging of Poly(lactide) Toughened with PEO-PBO Diblock Copolymer charles mccutcheon, Boran Zhao, Kailong Jin, Frank Bates, Christopher Ellison Poly(lactide) (PLA), a commercially available sustainable polymer, is an alternative to petroleum-based plastics. However, PLA lacks ductility and toughness limiting its applications. Small amounts of a liquid poly(ethylene oxide)-block-poly(butylene oxide) (PEO-PBO) diblock copolymer additive were blended with PLA to enhance its toughness. The incorporated PEO-PBO generated a macrophase-separated morphology with particle diameters of 0.2-0.9 μm. Adding 1.8 wt % PEO-PBO to PLA led to a 20-fold increase in elongation at break without affecting the bulk elastic modulus. The micromechanical deformation process of the PEO-PBO/PLA blend was investigated via in-situ small angle X-ray scattering during tensile testing. The volume of crazed material was proportional to the total surface area of the PEO-PBO particles and both quantities increased with PEO-PBO loading. Craze development was found to be independent of aging time. Therefore, the PEO-PBO/PLA blend was able to remain ductile compared to neat PLA. These results demonstrate that designing additives that promote deformation by crazing is an effective way to overcome the aging-induced embrittlement of glassy polymers. |
Monday, March 15, 2021 9:48AM - 10:24AM Live |
A08.00008: From Biomass Waste to Performance-Advantaged Materials: Structure-Property Relationships in Lignin-Based Polymers Invited Speaker: Thomas Epps Economic challenges continue to hamper the adoption of biobased polymers as alternatives to petroleum-based plastics. Generally, renewable polymers are too expensive due to the inherent variability in biobased feedstocks and the significant separation steps required to make purified monomer streams. Here, we demonstrate that materials with reproducible thermal and mechanical characteristics can be designed in a controlled and predictable manner from batches of monomers with complex and somewhat variable compositions, such as minimally processed bio-oils obtained from depolymerized lignin. As one example, we leveraged polymer structure-property relationships to fabricate high-performance pressure sensitive adhesives (PSAs) from compounds directly obtained from raw biomass (poplar wood) deconstruction. These PSAs, generated from biobased block copolymers, exhibited the nanoscale characteristics of conventional phase-separated materials and had peel forces and tack forces that were competitive with commercial tapes. As another example, we investigated the thermomechanical and environmental toxicity behavior of newly created bisguaiacol precursors and epoxy networks, for which the precursor compounds could be derived from lignin. These systems demonstrated drop-in potential, in both synthesis and materials properties, relative to petroleum-based analogues, yet most importantly, demonstrated reduced negative environmental impacts when screened by several common toxicity assays. In the above cases we employed raw biomass as our feedstock; however, we have recently demonstrated the versality of our strategy by expanding our feedstocks to other commercial scale inputs and developing key structure-property relationships. |
Monday, March 15, 2021 10:24AM - 10:36AM Live |
A08.00009: Self-catalytic Preparation of Epoxy Vitrimers: Mechanical performance, Adaptivity and Recyclability Jinwen Zhang The network structure of a vitrimer can undergo associative dynamic bond-interchange reactions at high temperatures to display a certain degree of adaptivity but remain crosslinked, so it behaves like a thermoset at service temperature. Epoxy vitrimers that work via the dynamic transesterification (DTER) mechanism have received the most study. I some earlier epoxy vitrimer works, the anhydride curing agent is purposely kept stoichiometrically deficient, which results in insufficient curing and hence poor mechanical and thermal properties. High catalyst concentration is often required to ensure fast repairing and shape changing properties, which may cause some potential problems in material applications. |
Monday, March 15, 2021 10:36AM - 10:48AM Live |
A08.00010: Systematic pyrolysis of commercial polypropylene for chemical recycling applications Amy Le, Nayoung Park, Ramanan Krishnamoorti Polypropylene is ubiquitous in plastics manufacturing where waste practices lack a sustainable approach and current efforts to recycle polypropylene diminish its mechanical properties. Chemical recycling, such as building copolymers with enhanced properties, is a promising alternative to traditional recycling. Breaking down and functionalizing polypropylene into oligomers allows for upcycling into other polymers. Here, we establish a robust protocol to oligomerize isotactic polypropylene through pyrolysis. While polypropylene pyrolysis has been previously studied, detailed tests to systematically adjust reaction parameters for short polymer and oligomer product characterization are underexplored. We assess kinetics, composition, rheological and thermo-physical properties of the polymer residue and distillate by adjusting key reaction parameters: temperature, reflux rate, reaction time, and catalysts. This protocol targets a pyrolyzed polymer residue comprising vinylidene end groups, with controlled thermo-physical and rheological properties, that can be further functionalized to incorporate into copolymers. Collectively, these studies aim to investigate the viscoelastic properties of functionalized polypropylene and establish heuristics for the design of a new class of polymers. |
Monday, March 15, 2021 10:48AM - 11:00AM Live |
A08.00011: Characterization of Fibril Hierarchical Self-Assembly of Sugar-based Poly(D-glucose carbonate) Amphiphilic Block Copolymers in Solution Jee Young Lee, Yue Song, Karen L. Wooley, Darrin John Pochan Motivated by the recent drive to replace petrochemical plastics for more renewable source-based materials, our efforts focus on designing and characterizing a next generation biomolecular-based polymer for solution assembly applications. Specifically, the solution chain and assembly behavior of sugar-derived poly(D-glucose carbonate) (PGC) molecules are analyzed in the production of nanoparticles. Unlike conventional vinyl-based polymers, the PGC system is characterized by its entire backbone composed of semiflexible, hydrophobic glucose monomers where its chain rigidity and local amphiphilicity created by the backbone are expected to impact the solution chain behavior. With a PGC-containing amphiphilic BCP system, we explore kinetically controlled assembly pathways for the hierarchical fibril construction. We show that while the stiffness of the PGC backbone impacts the local BCP chain conformation within the nanostructure, the backbone hydrophobicity drives the global unidirectional hierarchical fibril growth by the formation of soft patchy precursor particles. These results suggest polymers with unconventional backbone chemistries, frequently found in natural carbohydrate-based molecules, can shed light on the effects of unique chain properties on the assembly pathway. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700