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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Structural, Thermal, and Mechanical Characterization of a Thermally Conductive Polymer Composite for Heat Exchanger Applications

Polymer composites are being considered for numerous thermal applications because of their inherent benefits, such as light weight, corrosion resistance, and reduced cost. In this work, the microstructural, thermal, and mechanical properties of a 3D printed polymer composite with high thermal conductivity are examined using multiple characterization techniques. Infrared spectroscopy and X-ray diffraction reveal that the composite contains a polyphenylene sulfide matrix with graphitic fillers, which is responsible for the high thermal conductivity. Furthermore, differential scanning calorimetry determines that the glass transition and melting point of the composite are 87.6 °C and 285.6 °C, respectively. Thermogravimetric analysis reveals that the composite is thermally stable up to ~400 °C. Creep tests are performed at different isotherms to evaluate the long-term performance of the composite. The creep result indicates that the composite can maintain mechanical integrity when used below its glass transition temperature. Nanoindentation tests reveal that modulus and hardness of the composite is not significantly influenced by heating or creep conditions. These findings indicate that the composite is potentially suitable for heat exchanger applications.

36 MATERIALS SCIENCE↗
DOE OSTI2025

High-performance n-Type Polymers Based on Multiple Electron-withdrawing Groups Decorated ( E )-1,2-Di(thiophen-2-yl)ethene Building Blocks

The performance of n-type conjugated polymers lags far behind that of p-type polymers, which significantly restricts the development of organic electronics. The (E)-1,2-di(thiophen-2-yl)ethene (TVT) unit, owing to its unique advantages, has been widely applied in the design of p-type polymer semiconductors. Previous studies have demonstrated that introducing electron-withdrawing groups can lower the frontier orbital energy levels of polymers and enhance electron injection/transporting capabilities. Based on this, we proposed incorporating multiple electronwithdrawing groups, such as amide groups, fluorine atoms, and cyano groups, into the polymer backbones of TVT-based polymer to facilitate the electron transport. Here, we successfully designed and synthesized the polymers TVTDA-4FTVT and TVTDA-2F2CNTVT. Both polymers exhibited low frontier orbital energy levels. Due to its significantly higher crystallization tendency and favorable intermolecular packing structure, the organic field-effect transistor (OFET) device based on TVTDA-4FTVT demonstrated an electron mobility one order of magnitude higher than that of TVTDA-2F2CNTVT. TVTDA-4FTVT showed the highest electron mobility of 0.87 cm 2 ·V −1 ·s −1 , while TVTDA-2F2CNTVT exhibited the highest electron mobility of 0.049 cm 2 ·V −1 ·s −1 . Owing to its deeper lowest unoccupied molecular orbital (LUMO) level, the OFET devices based on TVTDA-2F2CNTVT showed good air stability after being placed in a natural environment for 15 d.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Thermo-mechanical deterioration and molecular degradation of 3D-printed methacrylate-based polymer in various chemical environments

The advancement of additive manufacturing (AM) has accelerated the development of stereolithographic (SLA) photo-curable resins, particularly methacrylate-based polymers, due to the ability to their high-resolution, robust mechanical properties, and suitability. However, their long-term performance in chemical environments remains poorly understood. This study investigates the extent and mechanisms of degradation on an SLA-printed methacrylate-based polymer subjected to various chemicals, including polar and non-polar solvents, as well as strongly acidic aqueous solutions over a 12-week accelerated aging period. A comprehensive analytical approach incorporating swelling kinetics, surface morphology, tensile and dynamic mechanical analysis (DMA), Fourier-transform infrared (FTIR) spectroscopy, and mass spectrometry (MS) was employed to characterize chemical absorption, structural integrity, and leached products. Results reveal that degradation severity is governed by both the polarity and reactivity of the chemical environment. Notably, exposure to 6 mol L -1 HNO₃ induced the most severe deterioration, with over threefold higher swelling compared to other media, and significant reductions in tensile strength, tensile modulus, and glass transition temperature (T g ). In contrast, specimens aged in non-polar solvents (xylene and dodecane) exhibited negligible chemical interaction and retained mechanical performance. FTIR and MS analyses identified acid-catalyzed hydrolysis of ester groups as prominent degradation pathways in acidic media, while diffusion-controlled plasticization prevailed in polar solvents. Furthermore, this study provides valuable insights into the chemical stability of SLA-printed polymers and develops predictive degradation profiles that are crucial for designing durable polymer systems for advanced industrial use.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Simultaneously improved J sc and V oc achieving 19.15% efficiency in ternary blend polymer solar cell containing a Y-type acceptor with thiophene based end groups

Simultaneously enhancing the short-circuit current density (J sc ) and open-circuit voltage (V oc ) of current state-of-the-art polymer solar cells (PSCs) containing wide bandgap polymers as donors and Y6 derivatives as acceptors is of great challenge but essential for further improvement of the photovoltaic performances. Here, in this work, two Y-type non-fullerene acceptors of BTP-T and BTP-TCl were designed and successfully synthesized with relatively weak electron-accepting thiophene based end groups, where blue-shifted absorption and upshifted LUMO energy levels were achieved to fill the well-known absorption gap at 700 nm of typical binary devices based Y-type molecules and rise the output voltage, respectively. Simultaneously increased J sc and V oc were achieved in ternary blend devices containing D18:BTP-eC9:BTP-TCl with a significantly improved PCE up to 19.15 %, which is over 7 % increase compared to the binary device. Our results illustrated the great potential of rational design of Y6 derivatives for constructing ternary PSCs to improve their performances.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Designing a Dynamic Material via Interlocking Kraft Lignin with Ultrahigh Molecular Weight Poly(ethylene oxide)

The environmental issues stemming from plastic waste and the excessive use of petroleum-based chemicals are both concerning and urgent. To effectively address this problem, we need to adopt a comprehensive approach involving developing more sustainable and renewable materials. These materials should be capable of demonstrating similar or even better performance than functional polymers synthesized from petroleum-based chemicals. Our research aims to develop more sustainable materials by leveraging the intrinsic characteristics of a natural polymer, lignin, a byproduct of the biorefinery industries. We utilized the three-dimensional branching structure of lignin as a material framework. We employed an approach to co-reactive melt processing of kraft lignin with aliphatic flexible chains of soft cross-linkers through the reaction of the cross-linker epoxy chain ends with lignin functional groups. Our study demonstrates that the interlocked structure formed from the co-blending of kraft lignin with ultrahigh molecular weight poly(ethylene oxide) and the cross-linking of lignin chains through a solvent-free process can manipulate the macromolecular interactions and relaxation. This manipulation results in materials that exhibit a wide range of thermomechanical properties and self-healing and shape memory effects, with drastically improved stiffness in a single material. We have explored the fundamental understanding of the macromolecular chain relaxation dynamics originating from the interlocking structure formation. In conclusion, this investigation utilized various techniques, including thermal, mechanical, rheology, and quasi-elastic neutron scattering.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Standalone Block Copolymer Nanoballoons: Decoupling Self-Assembly from Implementation in Nanomanufacturing

Here we report a facile method to produce isolatable hollow-core elastomeric vesicles, “nanoballoons”, prepared via block copolymer self-assembly in a polymer blend. Poly(isoprene-block-dimethylsiloxane) (PI-PDMS) diblock copolymers are blended with PDMS homopolymers (h-PDMS) as a “solvent” phase to template the self-assembly of PDMS-tethered vesicles with PI walls. The walls are subsequently crosslinked to yield mechanically stabilized elastomeric vesicles. The h-PDMS inner-core and matrix are separated from the vesicles by dialysis to yield the matrix-free nanoballoons. These objects, 0.3 – 1 μm in diameter, can be further reincorporated into a crosslinkable PDMS. Throughout the self-assembly, recovery, and reincorporation processes we apply several techniques including solvent dispersion/dynamic light scattering (DLS) measurements, transmission electron microscopy (TEM)/energy-dispersive X-ray spectroscopy (EDS), and small-angle X-ray scattering (SAXS) to provide a consilient body of evidence that the nanoballoon morphology is retained. Furthermore, this work presents advanced nanomanufacturing schema that illustrate the decoupling of the thermodynamic and dynamic factors that govern macromolecular self-assembly from the environment in which the self-assembled objects are deployed.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Electronic and Structural Properties of the Polymer-Electrolyte Interphase in Electrochemically Doped Polymers

The advance of soft, polymer-based (photo)electrochemical energy transformation and storage applications requires a framework for polymer and electrolyte design that includes a deep understanding of the polymer–electrolyte interphase. Here, we report on the investigations of two napthalenediimide (NDI)–bithiophene (T2)-based semiconducting copolymers using computational modeling and in situ, ex situ, and operando techniques to reveal how changes in electrolyte and polymer chemistry modulate the electronic and structural properties of polymer electrodes during electrochemical (de)doping. These systems are shown to host an ensemble of polarons, in contrast with the single polaron-like character often reported, whose properties vary with the nature of the local environment. Importantly, these polarons serve as reporters of the nanoscale environments in which they reside. We demonstrate that controlling the polymer and electrolyte chemistry regulates the nature of the charge carriers generated upon electrochemical doping and/or exciton dissociation in a photoelectrochemical solar cell: For instance, divalent counterions enable polaron and bipolaron formation at lower reducing potentials, while supporting more bipolaron formation than monovalent counterions. A novel application of NEXAFS reveals insights into charge (de)localization, providing a pathway for future investigation of electron transport mechanisms. Finally, simulations of polymer swelling of an amorphous interphase show that charge formation has a large impact on polymer swelling and ion penetration. These studies deliver insights to enable the control of charge-carrier and ion transport, the rates of electron transfer and catalytic efficiency, device stability, and overall device performance.

14 SOLAR ENERGY↗
DOE OSTI2024

Design Principles of Diketopyrrolopyrrole‐Thienopyrrolodione Acceptor 1 –Acceptor 2 Copolymers

Abstract The design principles of acceptor 1 –acceptor 2 copolymers featuring alternating diketopyrrolopyrrole (DPP) and thienopyrrolodione (TPD) moieties are investigated. The investigated series of polymers is obtained by varying the aromatic linker between the two acceptor motifs between thiophene, thiazole, pyridine, and benzene. High electron affinities between 3.96 and 4.42 eV, facilitated by the synergy of the acceptor motifs are determined with optical gaps between 1.37 and 2.02 eV. Grazing incidence wide‐angle X‐ray scattering studies reveal a range of film morphologies after thermal annealing, including face‐on, end‐on and superstructure edge‐on‐like crystallites. Conversely, all materials form thin edge‐on layers on the polymer–air interface, as demonstrated by multi‐elemental near‐edge X‐ray absorption fine‐structure spectroscopy. The benefit of the electron‐deficient linkers thiazole and pyridine is evident: In organic field effect transistors, electron mobilities of up to 4.6 × 10 −2 cm 2 V −1 s −1 are obtained with outstanding on/off current ratios of 5 × 10 5 , facilitated by the absence of detectable hole transport in these materials. Viability for all‐polymer solar cells is assessed in active layer blends with the donor polymer PM6, yielding a maximum average power conversion efficiency of 4.8% and an open circuit voltage above 1 V.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Plasma treatment on both adhesive tape and adherends for significantly enhanced CFRTP-related adhesive joints

Unlike existing literature that primarily concentrates on either the plasma treatment of adherends alone or solely on adhesive surfaces, this work leverages plasma modification of both adhesive in tape form and adherend surfaces to largely enhance the interfacial bonding between a thermoset-based adhesive tape and carbon-fiber-reinforced thermoplastic polymer (CFRTP) for structural bonding applications. Here, by conducting single lap shear tests on adhesively-bonded AA6061-CFRPPA (carbon-fiber-reinforced polyphthalamide) dissimilar joints, it is shown that the plasma treatment of adherends alone can increase the lap shear strength (LSS) of the joints by approximately 200% compared to non-treated counterparts. An additional plasma treatment of adhesive tape surfaces leads to even higher LSS improvement, reaching up to 315%, due to the formation of a denser crosslinked network of covalent bonds and a reduced area fraction of interfacial voids at the CFRPPA/adhesive interface. The highest plasma-enhanced LSS of the metal-CFRTP dissimilar joints rivals that of metal-metal joints, which is typically stronger than the joints associated with fiber-reinforced polymers. This study is important for achieving strong CFRTP-related structural components bonded using adhesive tape, providing better compatibility with plasma treatment and other joining methods like riveting compared to adhesive paste or liquid.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Impact of biomass ash content on biocomposite properties

Owing to its low cost and sustainable nature, lignocellulosic biomass has been utilized for reinforcing polymers, but it is crucial to understand the impact of high-ash concentrations in biomass on composite strength and processing. Biomass is not only desirable for biofuel production but could also have a strong market, if high-ash biomass is acceptable, for biocomposites. In this work, natural fibers (switchgrass and corn stover) were used to reinforce polylactic acid (PLA) to produce biocomposites. Natural fibers were pretreated to obtain fibers that contain different percentages of ash. The mechanical properties (such as Young's modulus, tensile strength, failure strain, storage modulus) of corn stover/PLA composites remained largely unaffected by the ash concentration of the biomass fibers, despite the large range of ash contents (2.2–11.9 wt%). Furthermore, the tensile strengths of switchgrass/PLA composites were slightly negatively affected by the ash concentration of the switchgrass fibers (0.7–2.1 wt%). Both the switchgrass/PLA and the corn stover/PLA composites exhibited a high-enough tensile strength (49–57 MPa) and suitable complex viscosity (2.0–7.0 kPa·s at the frequency of 3.2 rad/s). They are expected to be 3D-printable through an extrusion-based additive manufacturing process.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Laser-induced graphitization of polydopamine leads to enhanced mechanical performance while preserving multifunctionality

Polydopamine (PDA) is a simple and versatile conformal coating material that has been proposed for a variety of uses; however in practice its performance is often hindered by poor mechanical properties and high roughness. Here, we show that blue-diode laser annealing dramatically improves mechanical performance and reduces roughness of PDA coatings. Laser-annealed PDA (LAPDA) was shown to be >100-fold more scratch resistant than pristine PDA and even better than hard inorganic substrates, which we attribute to partial graphitization and covalent coupling between PDA subunits during annealing. Moreover, laser annealing provides these benefits while preserving other attractive properties of PDA, as demonstrated by the superior biofouling resistance of antifouling polymer-grafted LAPDA compared to PDA modified with the same polymer. Our work suggests that laser annealing may allow the use of PDA in mechanically demanding applications previously considered inaccessible, without sacrificing the functional versatility that is so characteristic of PDA.

36 MATERIALS SCIENCE↗
NASA NTRS2009

Electroactive Polymer (EAP) Actuators for Future Humanlike Robots

Human-like robots are increasingly becoming an engineering reality thanks to recent technology advances. These robots, which are inspired greatly by science fiction, were originated from the desire to reproduce the human appearance, functions and intelligence and they may become our household appliance or even companion. The development of such robots is greatly supported by emerging biologically inspired technologies. Potentially, electroactive polymer (EAP) materials are offering actuation capabilities that allow emulating the action of our natural muscles for making such machines perform lifelike. There are many technical issues related to making such robots including the need for EAP materials that can operate as effective actuators. Beside the technology challenges these robots also raise concerns that need to be addressed prior to forming super capable robots. These include the need to prevent accidents, deliberate harm, or their use in crimes. In this paper, the potential EAP actuators and the challenges that these robots may pose will be reviewed.

biomimetics↗
DOE OSTI2024

Techno-Economic Analysis and Life Cycle Assessment of the Production of Biodegradable Polyaliphatic–Polyaromatic Polyesters

Poly(butylene-adipate terephthalate) (PBAT) is a polyaliphatic–polyaromatic polyester that is biodegradable and has found application in several markets, making it a widely produced biodegradable polymer worldwide. However, the production of PBAT is carbon-intensive, as it relies on the use of petroleum-based monomers. There is, thus, significant interest in identifying polyesters that are biodegradable and less carbon-intensive (e.g., use of biomass- derived monomers). In this work, we develop a detailed process model (and an associated database) for the production of polyaliphatic–polyaromatic polyesters including petroleum-based PBAT and biomass-derived alternatives including poly(pentylene- adipate terephthalate) and poly(pentylene-adipate furandicarboxy- late). Techno-economic analysis (TEA) reveals that the production costs of these polyesters strongly depend on monomer costs (accounting for over 90% of the total production cost) and identifies market conditions under which biomass-based polyesters can be cost-competitive to petroleum-based PBAT. Life cycle assessment (LCA) shows that biomass-derived polyesters can reduce the global warming impact of PBAT by half. Altogether, the proposed TEA/LCA model aims to provide guidance into polyesters that are most promising and help assess their overall economic and environmental performance.

42 ENGINEERING↗
DOE OSTI2024

Creating Novel Gas Separation Constructs by Manipulating Free-Volume Distributions in Polymer-Grafted Nanoparticles

Polymer membranes are critical to sustainability applications, and in this work we focused on one key application, the efficient separation of gas mixtures. Despite their widespread use, important challenges remain in the use of polymer membranes in this context – i.e., finding membrane materials with selectively improved transport of the desired mixture component(s) while possessing enhanced strength and improved aging behavior relative to the best current benchmarks. The important separation figures of merit are the gas flux, which is proportional to the permeability, P i = D i × S i (Di is the gas diffusivity and S i its solubility coefficient) and selectivity (i.e., gas purity,α ij = P i /P j ). The goal is to simultaneously maximize P i and α ij . Most research to date has empirically targeted the development of new glassy polymers with improved separation performance. These include thermally rearranged (TR) polymers and polymers of intrinsic microporosity (PIMs).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Optically clear photo-polymerization resists for additive manufacturing of radiopaque parts

According to one embodiment, a method includes contacting a triiodobenzoic acid with an oxalyl chloride in a solvent whereby triiodobenzoyl chloride is formed, contacting diethanolamine with triiodobenzoyl chloride where triiodobenzoic diol amine is formed, and forming an acrylate of triiodobenzoic diol amine with acryloyl chloride where an organoiodine compound is formed. According to another embodiment, an optically clear photopolymer resist blend for additive manufacturing includes a radiopaque pre-polymer compound where the compound includes at least one of the following: iodine, bromine, tin, lead, or bismuth. The resist blend also includes a photoinitiator, a polymerization inhibitor, and a base pre-polymer.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Ionic Dopant-Induced Ordering Enhances the Thermoelectric Properties of a Polythiophene-Based Block Copolymer

Conjugated polymer-based block copolymers (CP-BCPs) are an unexplored class of materials for organic thermoelectrics. In this study, the authors report on the electronic conductivity (σ) and Seebeck coefficient (α) of a newly synthesized CP-BCP, poly(3-hexylthiophene)-block-poly (oligo-oxyethylene methacrylate) (P3HT-b-POEM), upon solution co-processing with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and subsequently vapor-doping with a molecular dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). It is found that the addition of the hydrophilic block POEM greatly enhances the processability of P3HT, enabling homogeneous solution-mixing with LiTFSI. Notably, interactions between P3HT-b-POEM with ionic species significantly improve molecular order and unexpectedly cause electrical oxidizing doping of P3HT block both in solution and solid-states, a phenomenon that has not been previously observed in Li-salt containing P3HT. Vapor doping of P3HT-b-POEM-LiTFSI thin films with F4TCNQ further enhances σ and yields a thermoelectric power factor PF = α 2 σ of 13.0 μW m -1 K -2 , which is more than 20 times higher than salt-free P3HT-b-POEM sample. Through modeling thermoelectric behaviors of P3HT-b-POEM with the Kang-Snyder transport model, the improvement in PF is attributed to higher electronic charge mobility originating from the enhanced molecular ordering of P3HT. The results demonstrate that solution co-processing CP-BCPs with a salt is a powerful method to control structure and performance of organic thermoelectric materials.

36 MATERIALS SCIENCE↗