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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Peptide-assisted supramolecular polymerization of the anionic porphyrin meso-tetra(4-sulfonatophenyl)porphine

Electronics made from biological materials are desirable for use in medical devices, biosensors, and soft robotics because they have properties inaccessible to current inorganic technologies. Here, a series of cationic peptides were developed to self-assemble with the anionic porphyrin meso-tetra(4-sulfonatophenyl)porphine (TPPS4) into supramolecular light-harvesting wires known as J-aggregates were developed. In addition to quantifying the binding events between each peptide and TPPS 4 , we found co-incubation with mixed peptides allowed TPPS 4 to bridge two different peptides at their terminal porphyrin-binding regions. The J-aggregates formed on macroscopic scale in near quantitative yield within similar to 3 h and readily interconverted with the soluble monomers upon cycling the pH; to our knowledge, this is the first report of a peptide-porphyrin system with such properties. This work has practical and conceptual relevance to the development of new bioelectronic materials.

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

Machine learning for polymeric materials: an introduction

We report that Polymers are incredibly versatile materials and have become ubiquitous. Increasingly, researchers are using data science and polymer informatics to design new materials and understand their structure-property relationships. Polymer informatics is an emerging field. While there are many useful tools and databases available, many are not widely utilized. Herein, we introduce the field of polymer informatics and discuss some of the available databases and tools. We cover how to share polymer data, approaches for preparing a dataset for machine learning and recent applications of machine learning to polymer property prediction and polymer synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Transport of penetrants in polymeric materials

Transport phenomena of chemical species in polymers underpin many applications. This mini-review discusses several key transport scenarios in polymer gels, melts and crosslinked polymer networks. Transport mechanisms of a wide variety of penetrant and polymer chemistries are discussed via activated hopping theory and cover across the rubbery, intermediate/deeply supercooled and glassy states of polymers. Moreover, we also discuss the ionic conductivity in polymer electrolytes, emphasizing the relationship between ion diffusion and the segmental relaxation of polymers and highlighting current challenges in the community. Finally, potential research directions are suggested concerning how external fields, such as mechanical force fields, active matter and self-propelling particles, affect the particle transport in polymers. This mini-review offers a general overview of motivations for studying penetrant transports in polymers and diverse mechanisms involved.

activated hopping↗
DOE OSTI2020

Recent advances in polymeric facilitated transport membranes for carbon dioxide separation and hydrogen purification

Membrane and membrane process have been widely considered as one of the best candidates for mitigating CO 2 emissions from the combustion or utilization of fossil fuels. Various amine-containing polymers constitute an important class of membranes, where the highly selective CO 2 transport is achieved by the facilitated transport mechanism. In this review, the amine–CO 2 chemistry is discussed in conjunction with the mechanism of the reaction-mediated CO 2 transport. A wide variety of amine-containing polymers are discussed based on two synthesis motifs: (a) polyamines with amino groups covalently bound to the polymer backbone and (b) small molecule amines embedded in a polymer matrix. This review concludes with the remarks on the facilitated transport membranes for post-combustion carbon capture (CO 2 /N 2 ) and hydrogen purification (CO 2 /H 2 ).

42 ENGINEERING↗
DOE OSTI2020

Molecularly engineering polymeric membranes for H 2 / CO 2 separation at 100–300 °C

Over the last two decades, polymers with superior H 2 /CO 2 separation properties at 100–300 °C have gathered significant interest for H 2 purification and CO 2 capture. This timely review presents various strategies adopted to molecularly engineer polymers for this application. We first elucidate the Robeson's upper bound at elevated temperatures for H 2 /CO 2 separation and the advantages of high-temperature operation (such as improved solubility selectivity and absence of CO 2 plasticization), compared with conventional membrane gas separations at ~35 °C. Second, we describe commercially relevant membranes for the separation and highlight materials with free volumes tuned to discriminate H 2 and CO 2 , including functional polymers (such as polybenzimidazole) and engineered polymers by cross-linking, blending, thermal treatment, thermal rearrangement, and carbonization. Third, we succinctly discuss mixed matrix materials containing size-sieving or H 2 -sorptive nanofillers with attractive H 2 /CO 2 separation properties.

42 ENGINEERING↗
DOE OSTI2021

Water-assisted mechanical testing of polymeric thin-films

Thin films with a nanometer-scale thickness are of great interest to both scientific and industrial communities due to their numerous applications and unique behaviors different from the bulk. However, the understanding of thin-film mechanics is still greatly hampered due to their intrinsic fragility and the lack of commercially available experimental instruments. In this review, we first discuss the progression of thin-film mechanical testing methods based on the supporting substrate: film-on-solid substrate method, film-on-water tensile tests, and water-assisted free-standing tensile tests. By comparing past studies on a model polymer, polystyrene, the effect of different substrates and confinement effect on the thin-film mechanics is evaluated. These techniques have generated fruitful scientific knowledge in the field of organic semiconductors for the understanding of structure–mechanical property relationships. Here, we end this review by providing our perspective for their bright prospects in much broader applications and materials of interest.

42 ENGINEERING↗
DOE OSTI2019

X-ray Phase Contrast Imaging of the Impact of a Single HMX Particle in a Polymeric Matrix

A thorough understanding of the mechanisms by which high explosives (HEs) are shock initiated, especially at the particle scale, is still in demand. One approach to explain shock initiation phenomenon is hot spot theory, which suggests that distributed energy in energetic material is localized due to shock or impact to generate the high temperatures for ignition. Here, we focus on the impact response of a HE polycrystalline particle, specifically HMX, in a polymer matrix. This represents a simplified analog of a traditional polymer-bonded explosive (PBX) formulation. A light gas gun, together with high-speed x-ray phase contrast imaging (PCI), was used to study the impact response of a single particle of production-grade HMX in a Sylgard-184® matrix. The high-speed x-ray PCI allows for real-time visualization of HE particle behavior. The experiments revealed that, at impact velocities of ~ 200 m s -1 , the energetic particle was cracked and crushed. When the impact velocity was increased to 445 m s -1 , a significant volume expansion of the particle was observed. This volume expansion is considered to be the result of chemical reaction within the HE particle.

42 ENGINEERING↗
DOE OSTI2020

X-ray Phase Contrast Imaging of the Impact of Multiple HMX Particles in a Polymeric Matrix

The initiation of high explosives (HEs) under shock loading lacks a comprehensive understanding: particularly at the particle scale. One common explanation is the hot spot theory, which suggests that energy in the material resulting from the impact event is localized in a small area causing an increase in temperature that can lead to ignition. This study focuses on the response of HMX particles (a common HE) within a polymer matrix (Sylgard-184 (R)), a simplified example of a polymer-bound explosive (PBX). These PBXs consist of multiple HMX particles in a single polymer-bound sample. A light gas gun was used to load the samples at impact velocities above 400 m/s. The impact events were visualized using X-ray phase-contrast imaging (PCI) allowing real-time observation of the impact event. The experiment used two different types of samples (multi-particle and two crystals) and found evidence of cracking and debonding in both sample types. Additionally, it was found that the multiple particle samples showed similar evidence of damage at lower velocities than that of single particle samples. This is an expected result as the multiple particles add additional interfaces for stress concentration and frictional heating.

42 ENGINEERING↗
DOE OSTI2023

Temporally Stable Supramolecular Polymeric Salts Enabling High-Performance 3D All-Aromatic Polyimide Lattices

Vat photopolymerization (VP) Additive Manufacturing (AM), in which UV light is selectively applied to cure photo-active polymers into complex geometries with micron-scale resolution, has a limited selection of aliphatic thermoset materials that exhibit relatively poor thermal performance. Ring-opening dianhydrides with acrylate-containing nucleophiles yielded diacrylate ester-dicarboxylic acids that enabled photo-active polyimide (PI) precursors, termed polysalts, upon neutralization with an aromatic diamine in solution. In situ FTIR spectroscopy coupled with a solution and photo-rheological measurements revealed a previously unknown time-dependent instability of 4,4'-oxydianiline (ODA) polysalts due to an aza-Michael addition. Replacement of the electron-donating ether-containing diamine with an electron withdrawing sulfone-containing monomer, e.g., 4,4'-diaminodiphenyl sulfone (DDS), prohibited the aza-Michael addition of the aromatic amine to the activated acrylate double bond. Novel DDS polysalt photocurable solutions are similarly analyzed and validated long-term stability, which enabled reproducible printing of polyimide organogel intermediates. Subsequent VP AM afforded 3-dimensional (3D) structures of intricate complexity and excellent surface finish, as demonstrated with scanning electron microscopy. In addition, the novel PMDA-HEA/DDS solution enabled the production of the first beam latticed architecture comprised of all-aromatic polyimide. Finally, the versatility of a polysalt platform for multi-material printing is further demonstrated by printing parts with alternating polysalt compositions.

36 MATERIALS SCIENCE↗
DOE OSTI2015

6-Thioguanine-loaded polymeric micelles deplete myeloid-derived suppressor cells and enhance the efficacy of T cell immunotherapy in tumor-bearing mice

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells that suppress effector T cell responses and can reduce the efficacy of cancer immunotherapies. We previously showed that ultra-small polymer nanoparticles efficiently drain to the lymphatics after intradermal injection and target antigen-presenting cells, including Ly6c hi Ly6g ₋ monocytic MDSCs (Mo-MDSCs), in skin-draining lymph nodes (LNs) and spleen. Here, we developed ultra-small polymer micelles loaded with 6-thioguanine (MC-TG), a cytotoxic drug used in the treatment of myelogenous leukemia, with the aim of killing Mo-MDSCs in tumor-bearing mice and thus enhancing T cell-mediated anti-tumor responses. We found that 2 days post-injection in tumor-bearing mice (B16-F10 melanoma or E.G7-OVA thymoma), MC-TG depleted Mo-MDSCs in the spleen, Ly6c lo Ly6g + granulocytic MDSCs (G-MDSCs) in the draining LNs, and Gr1 int Mo-MDSCs in the tumor. In both tumor models, MC-TG decreased the numbers of circulating Mo- and G-MDSCs, as well as of Ly6c hi macrophages, for up to 7 days following a single administration. MDSC depletion was dose dependent and more effective with MC-TG than with equal doses of free TG. Finally, we tested whether this MDSC-depleting strategy might enhance cancer immunotherapies in the B16-F10 melanoma model. We found that MC-TG significantly improved the efficacy of adoptively transferred, OVA-specific CD8 + T cells in melanoma cells expressing OVA. Ultimately, these findings highlight the capacity of MC-TG in depleting MDSCs in the tumor microenvironment and show promise in promoting anti-tumor immunity when used in combination with T cell immunotherapies.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Electro- and Photophysical Properties of Polymeric Film Composites with Monomers of Pyrido[2,1-b]benzothiazole Derivatives

It was found that film composites of the copolymer of styrene with octyl methacrylate with additions of the monomers of pyrido[2,1-b]benzothiazole derivatives have hole-type photoconductivity while the internal photoelectric effect in this medium is determined by the photogeneration of charge carriers from the monomers and transfer of nonequilibrium charge carriers through these monomers. In transition to a monomer with a more efficient conjugation system the photoconductivity and photovoltaic response are increased.

14 SOLAR ENERGY↗
DOE OSTI2018

A Review on Biodegradable Polymeric Materials Striving Towards the Attainment of Green Environment

Polymers are a chain of repeating monomers that can be either non-biodegradable or biodegradable with technical properties for a wide range of applications. The present scenario drives industries to develop new and eco-friendly materials to replace non-biodegradable materials to attain a clean and green environment. Significant research work has been carried out on the development of biocomposites based on biodegradable polymers and natural fibers. The review article addresses the wide range of biodegradable composites that are capable of undergoing degradation by various routes. Our main emphasis has been on the preparation and characterization of biocomposites, using various biodegradable polymers and natural fibers for wide applications like biomedical, packaging, aerospace, agriculture etc. It is clear that blending of reinforcing fibers and fillers with biodegradable polymers significantly enhanced the physical, chemical, biological, mechanical, thermal and biodegradation properties of the base matrix.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

A Novel Bacterial Polymeric Silk-Like Protein from a Petroleum Origin Bacillus sp. strain NE: Isolation and Characterization

This paper explores a novel silk-like protein (named Bacillus NE silk (BNES)) isolated from a petroleum origin bacterial strain belongs to the genus Bacillus. The successful characterizations for its chemical structure determination and protein composition have been performed. The results demonstrate that BNES protein is a new type of silk-like protein and has a prospective for applying as a new bacterial silk-like biomaterial. The amino acids constituents of silk-like protein showed that (Ala-Pro-Gly) rich-block protein, are the main major amino acids, while the protein M{sub wt}., was recorded around > ~ 400 kDa, which excelled those similar of natural silk. The degummed or purified silk-like protein was successfully electro-spinned for wet-electrospun silk-like nanofibers using electrospinning technique. Silk-like nanofibers gave an adequate and uniform ribbon-shape structure with average diameter of nanofiber around 110 nm. Meanwhile, the block silk-like protein exhibited high thermal degradation monitored at 140–373 °C, which close those of natural silkworm silk. The purified silk-like protein showed no toxic effect against Vero kidney normal cell-line even after 48 h of incubation, using MTT-assay test. The obtained results demonstrate that, silk-like protein from wild type bacterial origin has potential for use as novel fibrous biomaterials for biomedical and environmental applications.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Toward Greener Polymeric Blends: Study of PBAT/Thermoplastic Whey Protein Isolate/Beeswax Blends

This work evaluated the effects of partial substitution of PBAT by thermoplastic whey protein isolate (WPIT) with addition of beeswax through blends processing and their morphological, mechanical, structural, thermal and rheological properties. Whey protein isolate (WPI) was denatured at 90 °C, using glycerol as plasticizer, to be transformed in a thermoplastic material and subsequently blended with PBAT using a torque rheometer at 130 °C. Addition of 10 and 30% of WPIT in the PBAT matrix was investigated with and without beeswax. Blends were pressed as films with ~ 320 µm of thickness. Scanning electron microscopy (SEM) analysis of PBAT/WPIT blends films revealed the presence of domains. These domains are compounded of whey protein, while at the continuous phase a moderate degree of mixture between PBAT and WPIT was observed by Raman analyses. WPIT did not alter the degree of crystallinity and the glass-transition temperature (T{sub g}) of the PBAT in the blends. Thermogravimetric curves of the blends showed decomposition stages related to WPIT and PBAT phases. Thermal stability of blends decreased in comparison to WPIT, which was associated to the cleavage of disulfide bonds of WPIT during processing and causes other kind of interaction between components. Besides, blends containing WPIT remained non-rigid polymers with Young’s modulus below 70 MPa. The tensile strength and elongation at break decreased due the presence of WPIT. Beeswax did not influence the thermal and mechanical properties explored in this study.

36 MATERIALS SCIENCE↗