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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Role of solvation site segmental dynamics on ion transport in ethylene-oxide based side-chain polymer electrolytes

Ion conducting capability is often imparted to polymeric materials through short polyether side-chains, and yet the impact of this graft polymer architecture on ion solvation and conduction has not been fully explored. Here, we use a combination of impedance spectroscopy, vibrational spectroscopy, and atomistic molecular dynamics (MD) to compare the conductivity, ionic interactions, and polymer dynamics in a series of graft polyether electrolytes. We find that in poly[(oligo ethylene oxide)methyl ether methacrylate] (POEM), a widely used graft polymer electrolyte, the ionic conductivity drops more than an order of magnitude as the side-chain length is decreased from nine ethylene oxide (EO) units to three. This difference in conductivity is unexplained by differences in the calorimetric glass transition temperature (T g ), which varies only slightly with side-chain length. Furthermore, through vibrational spectroscopy and MD simulations we demonstrate that both linear and graft polyethers solvate Li⁺ ions effectively and dissociate them from large counterions, irrespective of side-chain length. Li⁺ ions do, however, show preferential solvation by EO units far from the methacrylate backbone. Similarly, EO units far from the backbone show enhanced segmental dynamics, while those near the immobile methacrylate group move substantially more slowly, as quantified by bond vector autocorrelation relaxation times. This heterogeneity in both ion solvation and local segmental relaxation explains variation in ion conductivity where material-averaged properties such as T g and number of free ions fail to do so. Importantly, the ionic conductivity is dictated primarily by the segmental mobility of the EO units which form effective solvation sites, rather than system-wide dynamics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Facilitated transport membrane with functionalized ionic liquid carriers for CO 2 /N 2 , CO 2 /O 2 , and CO 2 /air separations

CO 2 separations from cabin air and the atmospheric air are challenged by the very low partial pressures of CO 2 . In this study, a facilitated transport membrane (FTM) is developed to separate CO 2 from air using functionalized ionic liquid (IL) and poly(ionic liquid) (PIL) carriers. A highly permeable bicontinuous structured poly(ethersulfone)/poly(ethylene terephthalate) ( b PES/PET) substrate is used to support the PIL–IL impregnated graphene oxide thin film. The CO 2 separation performance was tested under a mixture feed of CO 2 /N 2 /O 2 /H 2 O. Under 410 ppm of CO 2 at 1 atm feed gas, CO 2 permanence of 3923 GPU, and CO 2 /N 2 and CO 2 /O 2 selectivities of 1200 and 300, respectively, are achieved with helium sweeping on the permeate side. For increased transmembrane pressure (>0 atm), a thicker PIL–IL/GO layer was shown to provide mechanical strength and prevent leaching of the mobile carrier. CO 2 binding to the carriers, ion diffusivities, and the glass transition temperature of the PIL–IL gels were examined to determine the membrane composition and rationalize the superior separation performance obtained. This report represents the first FTM study with PIL–IL carriers for CO 2 separation from air.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Highly stretchable ionically crosslinked acrylate elastomers inspired by polyelectrolyte complexes

Dynamic bonds are a powerful approach to tailor the mechanical properties of elastomers and introduce shape-memory, self-healing, and recyclability. Among the library of dynamic crosslinks, electrostatic interactions among oppositely charged ions have been shown to enable tough and resilient elastomers and hydrogels. In this work, we investigate the mechanical properties of ionically crosslinked ethyl acrylate-based elastomers assembled from oppositely charged copolymers. Using both infrared and Raman spectroscopy, we confirm that ionic interactions are established among polymer chains. We find that the glass transition temperature of the complex is in between the two individual copolymers, while the complex demonstrates higher stiffness and more recovery, indicating that ionic bonds can strengthen and enhance recovery of these elastomers. We compare cycles to increasing strain levels at different strain rates, and hypothesize that at fast strain rates ionic bonds dynamically break and reform while entanglements do not have time to slip, and at slow strain rates ionic interactions are disrupted and these entanglements slip significantly. Further, we show that a higher ionic to neutral monomer ratio can increase the stiffness, but its effect on recovery is minimal. Lastly, taking advantage of the versatility of acrylates, ethyl acrylate is replaced with the more hydrophilic 2-hydroxyethyl acrylate, and the latter is shown to exhibit better recovery and self-healing at a cost of stiffness and strength. The design principles uncovered for these easy-to-manufacture polyelectrolyte complex-inspired bulk materials can be broadly applied to tailor elastomer stiffness, strength, inelastic recovery, and self-healing for various applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Recyclable CFRPs with extremely high T g : hydrothermal recyclability in pure water and upcycling of the recyclates for new composite preparation

In recent years researchers have introduced different malleable and/or degradable thermosetting polymers to address the recyclability of traditional thermoset materials. Nonetheless, the mechanical properties and glass transition temperature (T g ) of these polymers are often compromised to achieve the desired depolymerization rate. In this work, a hydrothermally recyclable epoxy/anhydride thermosetting system with superior mechanical performance and high T g (>200 °C) was developed for carbon fiber reinforced plastic (CFRP) applications, using triethanolamine as the co-curing agent and tetraglycidyl methylenedianiline (TGDDM) as the epoxy matrix. The hydrothermal recycling of such cured systems is achieved at relatively low temperature (200 °C) without the addition of a catalyst. This mild recycling process decomposes the recyclable polymer matrix into an oligomer and imparts little damage to the valuable carbon fiber. The recycled carbon fiber and the decomposed polymer resin are reused to prepare a new CFRP. Here, this study has introduced a simple and practical approach for the preparation of recyclable CFRPs with high T g and a pathway for highly efficient closed-loop recycling, which sets up a framework for the future design of sustainable polymer composites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Trimerized small-molecule acceptors enable high-performance organic solar cells with high open-circuit voltage and prolonged life-time

Although the recent development of Y-series small-molecule acceptors (SMAs) has led to a dramatic increase in the power conversion efficiency (PCE) of organic solar cells (OSCs), the operational stability (device lifetime) of OSCs is inadequate for commercialization. In this study, we develop a new trimer acceptor (TYT), consisting of three Y-based molecules linked by electron-donating spacers, to realize an OSC with high-performance (PCE > 18%) and -stability (t 80% lifetime > 8000 h under 1 sun illumination, in which t 80% lifetime is the time required for the PCE of the OSC to reach 80% of its initial value). We demonstrate that the trimerization approach affords an acceptor, TYT, with an upshifted lowest unoccupied molecular orbital energy level, which, in turn, affords an efficient OSC with a high open-circuit voltage (0.964 V). In addition, the glass-transition temperature (T g ) of TYT (217 °C) is significantly higher than those of monomer (MYT, T g = 80 °C) and dimer (DYT, T g = 127 °C) acceptors, which effectively suppresses the molecular diffusion of TYT in a blend film with a polymer donor. Accordingly, a TYT-based OSC demonstrates a high PCE (18.2%) and long t 80% lifetime under 1 sun illumination (8454 h), outperforming MYT- and DYT-based OSCs that exhibit PCEs and t 80% lifetimes of 16.4% and 35 h, and 17.3% and 2551 h, respectively. Therefore, this study provides important guidelines for the design of electron acceptors in achieving OSCs with high performance and stability close to a commercial level.

14 SOLAR ENERGY↗
DOE OSTI2026

Accelerating ion transport by dynamic asymmetry of alternating polymer electrolytes

Polymer based electrolytes allow the absence of volatile components in batteries thus increasing their safety. Yet, they exhibit drawbacks based on their low conductivity. We have used an alternating polymer consisting of dimethyl siloxane (DMS) and ethylene glycol (EG) blocks to circumvent known disadvantages of the usually used polyethylene glycol (PEG). Incorporating dimethyl siloxane lowers the glass-transition temperature and thus reduces the segmental relaxation time, by dynamic asymmetry or internal plasticization of the constituting polymer blocks. The alternating structure ensures miscibility of the different components and hinders crystallization. Furthermore, the pure polymer, P(DMS 3 -alt-EG 4 ), shows a segmental relaxation time well in the range needed for polymer electrolytes. Mixtures of LiClO 4 and P(DMS 3 -alt-EG 4 ) show a drastically reduced temperature dependence of their DC conductivity in comparison to PEG based systems, resulting in an increase by two orders of magnitude at T = 5 °C and even three to four orders of magnitude at T = 0 °C. Addition of coordinating (acetonitrile) or non-coordinating (toluene) solvent increases conductivity either via additional plasticization or by weakening the Li-binding yet looking at the dynamics at low concentrations of additional solvent the mobility of the polymer is reduced. In conclusion, the solvent addition leads only at higher solvent concentration to a reduction in relaxation time.

Jakobi, Bruno [Louisiana State Univ., Baton Rouge,↗
DOE OSTI2025

Biobased chemical recycling: aminolysis of PET using renewable reagents and monomers to synthesize new semi-aromatic polyamides

Chemical recycling of PET is a method of depolymerizing polymer chains to monomeric components enabling the synthesis of second-generation materials with virgin-like quality. Commercial chemical recycling techniques rely upon high pressure methanolysis to create precursors capable of synthesizing a second-generation PET resin. However, despite the circular approach of methanolysis, a product with a very short lifespan and similar value is created. The approach of the current study is to utilize aminolysis as an ambient pressure technique to create precursors for higher value materials with longer lifespans to address the current crisis in plastic waste. Semi-aromatic polyamides (SAP) are desired in this circumstance because of their high melting point and heat resistance combined with good melt-processability similar to aliphatic polyamides. In this study SAPs were synthesized using precursors recovered from the aminolysis of PET employing biobased diamines and dicarboxylic acids. While aminolysis has been explored in previous studies, this work investigated the use of biobased components from castor oil: decamethylene diamine during recycling and sebacic acid during polymerization. Polymer synthesis resulted in the formation of SAPs similar to polyphthalamides (PPA) with novel structures given the aromatic portion from terephthalic acid (TPA) and aliphatic portion from the diamines and diacids. The synthesized materials exhibited excellent thermal stability with high glass transition temperatures. Novel polymers were created with varying aliphatic chain length to understand fundamental parameters needed to produce a valuable polymer from post-consumer waste.

High performance Applications↗
DOE OSTI2021

The relaxation behavior of supercooled and glassy imidacloprid

Employing dielectric spectroscopy, oscillatory shear rheology, and calorimetry, the present work explores the molecular dynamics of the widely used insecticide imidacloprid above and below its glass transition temperature. In its supercooled liquid regime, the applied techniques yield good agreement regarding the characteristic structural (alpha) relaxation times of this material. In addition, the generalized Gemant–DiMarzio–Bishop model provides a good conversion between the frequency-dependent dielectric and shear mechanical responses in its viscous state, allowing for an assessment of imidacloprid’s molecular hydrodynamic radius. In order to characterize the molecular dynamics in its glassy regime, we employ several approaches. These include the application of frequency–temperature superposition (FTS) to its isostructural dielectric and rheological responses as well as use of dielectric and calorimetric physical aging and the Adam–Gibbs–Vogel model. While the latter approach and dielectric FTS provide relaxation times that are close to each other, the other methods predict notably longer times that are closer to those reflecting a complete recovery of ergodicity. In conclusion, this seemingly conflicting dissimilarity demonstrates that the molecular dynamics of glassy imidacloprid strongly depends on its thermal history, with high relevance for the use of this insecticide as an active ingredient in technological applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Dynamics of polylactic acid under ultrafine nanoconfinement: The collective interface effect and the spatial gradient

Polymers under nanoconfinement can exhibit large alterations in dynamics from their bulk values due to an interface effect. However, understanding the interface effect remains a challenge, especially in the ultrafine nanoconfinement region. In this work, we prepare new geometries with ultrafine nanoconfinement ∼10nm through controlled distributions of the crystalline phases and the amorphous phases of a model semi-crystalline polymer, i.e., the polylactic acid. The broadband dielectric spectroscopy measurements show that ultrafine nanoconfinement leads to a large elevation in the glass transition temperature and a strong increment in the polymer fragility index. Moreover, new relaxation time profile analyses demonstrate a spatial gradient that can be well described by either a single-exponential decay or a double-exponential decay functional form near the middle of the film with a collective interface effect. However, the dynamics at the 1–2 nm vicinity of the interface exhibit a power-law decay that is different from the single-exponential decay or double-exponential decay functional forms as predicted by theories. Thus, these results call for further investigations of the interface effect on polymer dynamics, especially for interfaces with perturbed chain packing.

Chemistry↗
DOE OSTI2020

Tritium Effects on Aromatic Carbon–Loaded Polymers

By incorporating carbon nanotubes (CNTs) and graphene nanomaterials with aromatic sp2 carbon structures, we have specifically tuned filled ethylene propylene diene monomer elastomer (EPDM) seal and gasket composite materials for radiation resistance. Our results show that CNTs and graphene have an increased ability to stabilize the EPDM matrix compared to standard carbon black (CB) as a radiation-resistant filler. Here, graphene outperforms both CNT and CB fillers when considering surface damage under conditions where beta exposure is an issue. Both graphene and CNT fillers offer significantly reduced changes in glass transition temperature under prolonged exposure to tritium compared to CB-filled standards, with a 2.5-fold and almost 5-fold reduction, respectively. Thus, CNT- and graphene-filled O-ring materials could be designed that would maintain acceptable seals significantly longer than currently used composites.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Nanoscale viscosity of confined polyethylene oxide

Complex fluids near interfaces or confined within nanoscale volumes can exhibit substantial shifts in physical properties compared to bulk, including glass transition temperature, phase separation, and crystallization. Because studies of these effects typically use thin film samples with one dimension of confinement, it is generally unclear how more extreme spatial confinement may influence these properties. In this work, we used x-ray photon correlation spectroscopy and gold nanoprobes to characterize polyethylene oxide confined by nanostructured gratings (<100nm width) and measured the viscosity in this nanoconfinement regime to be ~500 times the bulk viscosity. Here, this enhanced viscosity occurs even when the scale of confinement is several times the polymer's radius of gyration, consistent with previous reports of polymer viscosity near flat interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure evolution during near- T g annealing and its effect on shear banding in model alloys

By performing extensive molecular dynamics simulations, we investigate herein the deformation behavior in A l 90 S m 10 and C u 64.5 Z r 35.5 alloys after elongated isothermal annealing in the vicinity of the glass-transition temperature ( T g ). Different microstructural response to the annealing process was observed: A l 90 S m 10 maintains the glassy structure with improved energetic stability, enhanced short-range order (SRO), and a more pronounced spatial network that extends beyond the first atomic shell, while C u 64.5 Z r 35.5 forms nanocrystalline Laves C u 2 Zr phases. Shear banding occurs in both annealed systems under shear loading. For A l 90 S m 10 , the spatial network formed by the local clusters characterizing the SRO of the system is significantly weakened but remains appreciable in the shear band. In contrast, the crystalline ordering in the C u 64.5 Z r 35.5 is completely destroyed during shear banding. Consequently, while displaying higher yield strength, the annealed C u 64.5 Z r 35.5 sample appears to be less ductile. By carefully examining the effect of microstructures on the structural ordering in the shear band and the consequent mechanical response, our work contributes to a better understanding of the deformation mechanism of amorphous alloys as compared with that in crystalline materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Well-designed Crosslinked Polymer Electrolyte Enables High Ionic Conductivity and Enhanced Salt Solvation

A new facile single-step method to fabricate crosslinked polymer electrolyte membranes consisting of branched poly(ethyleneimine), (PEI) and poly(ethylene oxide), (PEO) is demonstrated. The membranes exhibit excellent ionic conductivity (1.2 × 10 –3 S cm –1 at 80 °C) with minimal addition of plasticizer (20 wt%). The amine functional group in the PEI-PEO crosslinked matrix provides Lewis basic and hydrogen bonding characteristics that facilitate the dissolution of lithium salt and enables a higher cation transport number than a PEO crosslinked matrix. The glass transition temperature, degree of crystallinity, and room temperature storage modulus increases with decreasing crosslink density and increasing ratio of free amines. The resultant ionic conductivity and mechanical strength can be flexibly tailored by varying the molar ratio of free amine moieties in the crosslinked PEI-PEO matrix. This study provides an improved synthesis method, in-depth characterization, and fundamental insights on the effect of free amine moieties on the transport properties of a highly conductive gel polymer electrolyte.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Evaluating efficacy of different UV-stabilizers/absorbers in reducing UV-degradation of lignin

Abstract Susceptibility of wood to UV degradation decreases the service life of wood products outdoors. Organic UV absorbers (UVAs) and hindered amine light stabilizers (HALSs), as well as inorganic UVAs, are added to coatings to improve the UV stability of coated-wood products. Although about 85% of UV radiation is absorbed by lignin in the wood, it is unclear which UV stabilizers can minimize lignin degradation. In this study, the photodegradation of softwood organosolv lignin was monitored over 35 days of UV exposure. Changes in lignin properties were assessed using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and phosphorus-31 nuclear magnetic resonance spectroscopy ( 31 P NMR). It was found that the aromatic rings of lignin underwent significant degradation, resulting in increased glass transition temperature and molecular weight of lignin. Subsequently, 18 different additives were mixed with lignin and exposed to UV irradiation. The analysis of samples before and after UV exposure with FTIR revealed that inorganic UVAs (cerium oxide and zinc oxide) and a mixture of organic UVAs and HALSs (T-479/T-292, T-5248, and T-5333) were the most effective additives in reducing lignin degradation. This study can help coating scientists to formulate more durable transparent exterior wood coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Fully Recyclable Advanced Composites with Reduced Cure Times for Improved Manufacturing Efficiency

At Cyclotron Road, the participant team from Mallinda focused its research efforts on developing its Polyimine chemistry for commercial applications. The value-differentiating characteristics of the technology are predicated on the chemical reversibility of the system which opens the door for a number of industrial applications. In short, the company’s technology is a highly crosslinked thermoset polymer network that can exchange covalent bonds within the polymer matrix when the polymer is heated to the glass transition temperature of the material. This leads to a resin system that can alternate between rigid and semi-rigid states; allowing for compression molding, and surface welding of thermosetting composite materials made with polyimine polymers. This research project worked towards improving the thermal properties of its resin from 80 °C to over 260 °C. The improved properties of Mallinda’s resin unlocks development potential within the automotive and aerospace markets where advance composite materials require stringent performance requirements and elevated operating temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Development of a Kollidon 90F-PEG300-Glycerin Binder for PZT 95/5 Ceramic Processing

This SAND Report documents the development of organic binder system for PZT 95/5 consisting of Kollidon 90F, PEG300, and glycerin. Binders are a critical component in the manufacture of ceramic components. Low performing binders can result in poor yield and lower performance of ceramic components. This study sought to develop a well performing binder system for PZT 95/5 ceramics to support Ferroelectric Neutron Generator manufacturing. The study explored the glass transition temperature, powder compaction properties, green strengths, and thermal decomposition over a wide composition range. An optimal composition was found consisting of 1.3 wt.% Kollidon 90F, 0.5 wt.% PEG300, and 0.2 wt.% glycerin, and incorporating humidity conditioning . The results showed that the optimized binder exhibited improved compaction performance and enhanced green strength compared to a baseline binder and at lower loading. Further, sintered PZT 95/5 parts prepared using the optimized binder exhibited ~5% improved polarization performance without alteration to the microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Silicone Resins for Vat Polymerization Printing

This paper reviews research of silicone-based resins for vat polymerization printing (VPP). Silicone resins are used commonly in other 3D printing technologies because of their desirable properties. Silicones are chemically inert, oxidatively, and thermally stable, and have the lowest glass transition temperature of any polymer. Creating silicone resins processable by VPP is challenging because VPP requires low viscosity liquid resin that quickly photopolymerizes. This review will summarize VPP technologies, resin chemistries, and recent research of silicone VPP resins.

36 MATERIALS SCIENCE↗
DOE OSTI2024

RESIN: Responsible Innovation for Highly Recyclable Plastics - TASK 4: Risk Assessment Framework

This report covers the entirety of Task 4, but its main purpose is to deliver milestones ML4.4 and ML4.5, the last two SOPO milestones under Task 4. ML4.4 reports on the compatibility of polymer properties that affect both environmental performance and functional performance and the tradeoffs involved in turning these properties to the benefit of each. ML4.5 presents a complete set of information on the critical properties of benign target products, where benign products are defined as those with the shortest environmental lifetime which meet performance requirements. To support and provide context to the discussions of ML4.4 and ML4.5 and to provide a complete picture of Task 4, milestones 4.1-4.3 are briefly summarized at the beginning of the report. The discussion of ML4.4 introduces the notion of polymer persistence as a proxy for environmental risk. It then discusses the development and comparison of two machine leaning models explored for estimating polymer degradation rates, a random forest (RF) classifier and an RF regressor. Given the advantage of continuous outputs rather than simple classes, the RF regressor was incorporated in the Excel risk calculator, which to this point could implement the objectives of subtasks 4.1-4.3, estimating polymer release and redistribution. The ML4.4 discussion then addresses the effect of each of the three polymer features used by the RF regressor on polymer functional performance. These features are number molecular weight (Mn), glass transition temperature (T g ) and heat of fusion (H fus ). The discussion of ML4.5 reviews the conceptual framework of the risk model, which served as the foundation for developing the Excel risk calculator and describes the use of, and assumptions within, the calculator. Appendix A is further provided as a user’s guide for the calculator. To demonstrate how the calculator is intended to be used by developers in the design of low-risk polymers, an analysis of 27 hypothetical polymers defined by varying values for the three polymer features used by the RF regressor is presented. The range of parameter values selected produces estimates of polymer degradation rates and lifetimes that may be typical of various consumer products made from polyurethane polymers and shows how changes in polymer features affect lifetimes. The demonstration also predicts the final distribution of released polymer materials in environmental compartments as a function of consumer product mix and assumed leakage rates of end-of-life processes. Lastly, this report summarizes the achievement of Task 4 goals from original conception to final delivery and discusses how and to what degree to which each subtask goal was achieved.

36 MATERIALS SCIENCE↗