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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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67 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Functional stimuli-responsive polymers on micro- and nano-patterned interfaces

Micro- and nano-patterned surfaces offer precise control over morphology and chemical composition, enhancing the stability, durability, and functionality of coating materials. When combined with stimuli-responsive polymers, these surfaces gain dynamic adaptability, enabling reversible binding, reusable sensing, and selective molecular capture. Furthermore, while recent review articles have explored various aspects of stimuli-responsive materials, from hydrogel patterns for bioanalytical applications to shape-morphing hydrogels for soft robotics and sensors, a comprehensive review focused on the integration of smart polymers with micro- or nano-patterned interfaces remains absent. This review addresses key surface patterning techniques, including soft lithography, colloidal lithography, and polymer brush photolithography, as well as advances in surface-initiated polymerization methods, such as surface-initiated controlled radical polymerization (SI-CRP). In addition, we discuss recent progress in integrating stimuli-responsive polymers with patterned surfaces to create advanced, functional materials.

Colloidal lithography↗
DOE OSTI2023

Relaxation dynamics of water in the vicinity of cellulose nanocrystals

Water molecules near cellulose nanocrystals (CNCs; produced via the sulfuric acid-catalyzed hydrolysis of wood pulp) are believed to relax slower than those in the bulk liquid, which may result in unique properties of CNC aqueous dispersions. Herein this study analyzed the polarization behavior of water molecules in CNC aqueous dispersions and other reference samples using a dielectric relaxation spectroscopy (DRS) technique in the microwave frequency range (0.2–20 GHz). As the CNC concentration increases, two slow relaxation components become prominent. The comparison with DRS data of aqueous dispersions of nanoporous silica, polyvinyl alcohol (PVA), and hairy CNC (HCNC) with amorphous chains protruding from both ends suggested that these slow relaxation modes of water near CNC surfaces cannot be attributed to direct hydrogen bonding interactions with the hydroxyl (OH) groups exposed and immobilized at the solid surface. Instead, they are similar to the water molecules interacting with OH groups attached to flexible polymer chains. Molecular dynamics (MD) simulations of the polarization behavior of water near the (110) facet of cellulose Iβ crystals confirmed that the interactions of water molecules with the cellulose crystal surface do not cause slower relaxations in the frequency range studied via the DRS. These results indicated that the CNC surface cannot be depicted with the crystallographic facets of cellulose Iβ; instead, it resembles a polymer-brush surface on which the short glucan residues or fragments of the strong acid-catalyzed hydrolysis process are swollen and extended into the aqueous phase.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Using Nanofiller Assemblies to Control the Crystallization Kinetics of High-Density Polyethylene

Polyethylene-grafted nanoparticles (NPs) are organized into a variety of assemblies in a polydisperse polyethylene melt by tailoring the graft density and molecular weights of the graft chains. Under these conditions we systematically vary NP assemble state and study is consequences on crystal nucleation and growth rates. We find that the nucleation rate is suppressed below that of the unfilled polymer for good NP spatial dispersion. However, poorer dispersion, which leads to the formation of NP assemblies, can accelerate nucleation likely by providing multiple heterogenous sites due to topographical features. We find that a key parameter, the chain overcrowding in the brush, can predict these nucleation trends – in this language, the most enhanced nucleation rate is found when the grafts are the most overcrowded, and hence the least interpenetrated with the matrix chains. This result is consistent with one other literature result which utilized short crystallizable polyethylene glycol grafts in short PEO matrices. The growth kinetics were retarded for all nanocomposites, their temperature dependences were essentially equal to that for the pure polymer (in the absence of NPs) – the NPs thus do not affect secondary nucleation, indicating that the transport of the matrix to the growth front is the rate determining step. Thus, evidently the increase in matrix viscosity, or reduction in growth rates, is directly determined by the agglomeration state of the NPs. These results are consistent with past works with bare silica NPs in PEO, and with silica NPs grafted with amorphous chains in a PEO matrix, suggesting that growth kinetics in these systems apparently follow “universal” behavior. Additionally, there are initial hints that the ratio of the effective surface area of the NP clusters per unit matrix volume provides a unified description of the NP induced confinement that slows growth kinetics. Furthermore, our work thus shows that there is an evolving understanding of the role of NPs on crystallization kinetics, in particular crystal growth where trends appear to be independent of the grafts ability to crystallize.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Superstructural phase transitions in polymer-grafted nanooctahedra

Superlattices of polyhedral nanocrystals exhibit emergent properties defined by their structural arrangements, but native nanocrystal ligands often limit their programmability. Polymeric ligands address this limitation by enabling tunable nanocrystal softness through modifications of polymer molecular weight and grafting density. Here, we investigate phase transitions in polymer-grafted nanooctahedra by varying polymer length, nanocrystal size, truncation, and ligand density. In two-dimensional superlattices, longer polymers or smaller nanooctahedra induce a transition from orientationally ordered to hexagonal rotator lattices. In three-dimensional superlattices, increasing polymer length drives transitions from Minkowski to body-centered cubic and plastic hexagonal close-packed phases, while higher grafting densities further enable transitions to simple hexagonal phases. Polymer brush and thermodynamic perturbation theories, supported by Monte Carlo simulations, uncover the entropic and enthalpic forces that govern these transitions. This work highlights the versatility of polymer-grafted anisotropic nanocrystals as building blocks for designing hierarchical superstructures and metamaterials with customizable properties.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Stainless Steel Coating Test Report

A process was developed to coat 316L stainless steel pieces having very low levels of fixed contamination on their surface (~100 dpm/100 cm²). The coating process served to significantly decrease the likelihood of any fixed contamination becoming loose contamination due to physical shocks. Prior to coating, the stainless steel was etched with a commercial methane sulfonic acid (MSA) solution in a heated ultrasonic bath, rinsed with deionized water, cleaned with a basic detergent solution, and then rinsed with deionized water. The MSA etched the surface of the stainless-steel pieces, creating a more favorable surface on which the coating could adhere. Due to the short timeline of the project, only commercially available clear coating products were considered. The clear coating had to be wear-resistant, shock resistant, radiation resistant, and have high adhesion to the surface of the stainless steel. Adhesion of coatings to stainless steel is notoriously difficult. A commercial, high molecular weight polymer coating was found that met these requirements. The adhesion properties of this coating to stainless steel are very good, and are significantly improved by the etching process. The etching process results in a higher surface area that is free of debris and other residues, making the surface much more wetable, and at the same time creating a favorable surface topography for adhesion. The polymer in its uncured form is a low viscosity liquid. It can be applied by brush or pipette, and it cures in air alone, but heat is required to speed up curing and attain the highest performance of the cured polymer. As the project progressed, the project team became interested in the composition of the selected commercial polymer coating, and in ways that this polymer coating could be made more wear resistant and potentially more radiation resistant. Nano-particle addition was chosen as the preferred way to achieve higher performance. Therefore, a series of tests were planned and performed. This report summarizes these tests, and presents the results.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Structural specificity of mucosal-cell transport and metabolism of peptide drugs: implication for oral peptide drug delivery

The brush border membrane of intestinal mucosal cells contains a peptide carrier system with rather broad substrate specificity and various endo- and exopeptidase activities. Small peptide (di-/tripeptide)-type drugs with or without an N-terminal alpha-amino group, including beta-lactam antibiotics and angiotensin-converting enzyme (ACE) inhibitors, are transported by the peptide transporter. Polypeptide drugs are hydrolyzed by brush border membrane proteolytic enzymes to di-/tripeptides and amino acids. Therefore, while the intestinal brush border membrane has a carrier system facilitating the absorption of di-/tripeptide drugs, it is a major barrier limiting oral availability of polypeptide drugs. In this paper, the specificity of peptide transport and metabolism in the intestinal brush border membrane is reviewed.

Review, Tutorial↗
DOE OSTI2020

Unexpected Conformational Behavior of Poly(poly(ethylene glycol) methacrylate)-Poly(propylene carbonate)-Poly(poly(ethylene glycol) methacrylate) (PPEGMA-PPC-PPEGMA) Amphiphilic Block Copolymers in Micellar Solution and at the Air-Water Interface

Self-assemblies (bulk micelles and Langmuir monolayers) of a new amphiphilic block copolymer, poly(poly(ethylene glycol) methacrylate)-poly(propylene carbonate)-poly(poly(ethylene glycol) methacrylate) (PPEGMA-PPC-PPEGMA), were investigated in dilute aqueous solution and at the air-water interface. An important feature that distinguishes PPEGMA-PPC-PPEGMA from conventional linear PEG-based polymer surfactants is that in the hydrophilic PPEGMA block the PEG moieties exist as side chains attached to the poly(methacrylate) (PMA) backbone. This study was performed using three PPEGMA-PPC-PPEGMA samples having an identical PPC molecular weight (5.6 kDa) and different PPEGMA molecular weights (7.3, 2.8 and 2.1 kDa on either side) (named as “G7C6G7”, “G3C5G3”, and “G2C6G2”, respectively). Cryo-TEM images revealed that G2C6G2 micelles form large clusters, whereas G7C6G7 micelles exist as unimers; the behavior of G3C6G3 is intermediate. The average core surface distance between two adjacent G2C6G2 micelles in a cluster was estimated to be only about 3.7 nm, which suggests that in the micelle corona layer only the PEG side chains (but not the PMA backbone) exist as hydrated brush chains. A calculation showed that at the small micelle separation distance observed, the van der Waals attractive forces become significant, and are thus likely responsible for the cluster formation. Steady shear rheometry measurements confirmed that G2C6G2 micelles are indeed only weakly bound in clusters, and these micelle clusters are thus prone to breakup even under mild steady shear. The micelle breakup force estimated from the shear viscosity data is in reasonable agreement with an estimate obtained from the theoretical van der Waals interaction potential. Langmuir monolayers formed at the air-water interface by PPEGMA-PPC-PPEGMA were also characterized; surface pressure-area measurements were performed. Detailed features of the surface pressure-area isotherms further supported that only the PEG side chains are hydrated in the subphase, while the PMA backbone remains unhydrated and situated on the water surface.

Lee, Jaewon↗
DOE OSTI2024

Self-assembled complex micelle phase stability in ABA-type triblock copolymers and related core-shell bottlebrushes

We report the synthesis and temperature-dependent morphologies of a series of polylactide--poly (-decalactone)--polylactide (LDL) triblock copolymers with M n = 16.0 – 18.1 kg / mol and volume fractions f L = 0.27 – 0.31 and associated core-shell bottlebrush (csBB) polymers, which derive from enchaining LDL triblocks through a polymerizable midchain functionality. While the LDL triblocks form micellar Frank-Kasper A15 and phases due to the conformational asymmetry of this monomer pair, the csBB morphologies sensitively depend on the backbone degree of polymerization ( N bb ). At low N bb values, micellar Frank-Kasper phases with the brush backbone situated in the matrix domain are stable, albeit with a modest reduction in the mean interfacial curvature evidenced by a to A15 order-to-order transition. However, larger N bb values drive csBBs to form hexagonally packed cylinders phases. This N bb -dependent phase behavior is rationalized in terms of a star-to-bottlebrush transition. At low N bb values, the csBBs are akin to star polymers with pointlike junctions that can support complex micelle packings. As N bb increases, the csBBs adopt cylindrical molecular geometries with extended backbones situated in the matrix domain that prefer hexagonally packed cylinders morphologies. Published by the American Physical Society 2024

Materials Science↗
DOE OSTI2020

Effect of Molecular Weight and Layer Thickness on Dielectric Breakdown Strength of Neat and Homopolymer Swollen Lamellar Block Copolymer Films

Designing next-generation lightweight pulsed power devices hinges on understanding the factors influencing the energy storage performance of dielectric materials. Polymer dielectric films have a quadratic dependence of energy storage on the voltage breakdown strength and strategies to enhance the breakdown strength are expected to yield a path toward high energy storage densities. Highly stratified lamellar block copolymer (L-BCP) films of model polystyrene-b-polymethylmethacrylate (PS-b-PMMA) exhibited as much as ~50% enhancement in breakdown voltage (E BD ), (225 % increase in stored energy density, U~ E BD 2 ), compared to unordered as-cast L-BCP films. Such an energy density using amorphous polymer is on par with industry-standard semi-crystalline biaxially oriented polypropylene (BOPP), and as such a notable development in the field. This work develops a deeper understanding of the molecular mechanisms of E BD enhancement in L-BCP films, due to combination of interface formation and spatial isolation of the chain ends into segregated zones. We further confirm the role of chain ends in the breakdown process blending a low M n L-BCP with matched M n homopolymers to attain same layer spacing as neat L-BCP of higher M n . E BD shows a significant decrease at low homopolymer fractions due to increased net chain end density within swollen ordered L-BCP domains in wet-brush regime, followed by increased E BD due to layer thickness increase via segregated “interphase layer” formation by excess homopolymers. Notably, E BD of homopolymer swollen L-BCPs is always lower than neat L-BCP of the same domain spacing, due to overall adverse chain ends contribution from homopolymers. These findings provide important selection rules for L-BCPs for designing next-generation flexible electronics with high energy density solid-state BCP film capacitors.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Programmable Site-Specific Functionalization of DNA Origami with Polynucleotide Brushes

Combining surface-initiated, TdT (terminal deoxynucleotidyl transferase) catalyzed enzymatic polymerization (SI-TcEP) with precisely engineered DNA origami nanostructures (DONs) presents an innovative pathway for the generation of stable, polynucleotide brush-functionalized DNA nanostructures. Here we demonstrate that SI-TcEP can site-specifically pattern DONs with brushes containing both natural and non-natural nucleotides. The brush functionalization can be precisely controlled in terms of the location of initiation sites on the origami core and the brush height and composition. Coarse-grained simulations predict the conformation of the brush-functionalized DONs that agree well with the experimentally observed morphologies. We find that polynucleotide brush-functionalization increases the nuclease resistance of DONs significantly, and that this stability can be spatially programmed through the site-specific growth of polynucleotide brushes. The ability to site-specifically decorate DONs with brushes of natural and non-natural nucleotides provides access to a large range of functionalized DON architectures that would allow for further supramolecular assembly, and for potential applications in smart nanoscale delivery systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Ionic Liquid‐Driven Modulation of DNA Brush Morphology on Nanoparticle Surfaces

Here, the morphology of DNA is strongly influenced by its surrounding environment, including factors such as pH, salt type and valency, and the presence of polymers. Inorganic salts are known to reduce the DNA chain length through mechanisms like electrostatic screening and ion bridging. In contrast, ionic liquids, a new class of organic salts, have previously been found to increase the DNA chain length, indicating a distinct mode of interaction between the ionic liquid and DNA chains. This study utilizes self-assembled DNA-AuNPs as a model system to examine changes in the DNA chain morphology and the nanoscale interaction mechanisms in an ionic liquid environment. The DNA chain lengths are measured in solution using X-ray scattering measurements at varying concentrations of two imidazolium ([$BMIM$] acetate and [$EMIM$] acetate) based ionic liquids. Additionally, Molecular Dynamics (MD) simulations are performed mimicking the experimental system. Our results suggest an interplay of electrostatic and groove-binding interactions governing the DNA chain morphology, which depends on IL concentration and the composition of the DNA chains. It has been found that for DNA chains with majority ssDNA, electrostatic interaction dominate, however with increasing composition of double strands, the DNA chains exhibit compaction due to a non-electrostatic hydrophobic groove-binding mechanism.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

LinkML: an open data modeling framework

Background Scientific research relies on well-structured, standardized data; however, much of it is stored in formats such as free-text lab notebooks, nonstandardized spreadsheets, or data repositories. This lack of structure challenges interoperability, making data integration, validation, and reuse difficult. Findings LinkML (Linked Data Modeling Language) is an open framework that simplifies the process of authoring, validating, and sharing data. LinkML can describe a range of data structures, from flat, list-based models to complex, interrelated, and normalized models that utilize polymorphism and compound inheritance. It offers an approachable syntax that is not tied to any one technical architecture and can be integrated seamlessly with many existing frameworks. The LinkML syntax provides a standard way to describe schemas, classes, and relationships, allowing modelers to build well-defined, stable, and optionally ontology-aligned data structures. Once defined, LinkML schemas may be imported into other LinkML schemas. These key features make LinkML an accessible platform for interdisciplinary collaboration and a reliable way to define and share data semantics. Conclusions LinkML helps reduce heterogeneity, complexity, and the proliferation of single-use data models while simultaneously enabling compliance with FAIR (Findable, Accessible, Interoperable, and Reusable) data standards. LinkML has seen increasing adoption in various fields, including biology, chemistry, biomedicine, microbiome research, finance, electrical engineering, transportation, and commercial software development. In short, LinkML makes implicit models explicitly computable and allows data to be standardized at their origin. LinkML documentation and code are available at https://linkml.io/.

AI-ready data↗
DOE OSTI2021

Plasma-Initiated Graft Polymerization of Acrylic Acid onto Fluorine-Doped Tin Oxide as a Platform for Immobilization of Water-Oxidation Catalysts

The discovery of new and versatile strategies for the immobilization of molecular water-oxidation catalysts (WOCs) is crucial for developing clean energy conversion devices [e.g., (photo)electrocatalytic cells for water splitting]. The traditional approach for surface attachment to transparent conductive oxides [e.g., fluorine doped tin oxide (FTO)] is via synthetic modification of the ligand architecture to incorporate functional groups such as carboxylic acids (-COOH) or phosphonates (-PO 3 H 2 ) prior to immobilization. However, challenges arising from desorption and the cumbersome derivatizations steps have limited the scope and applications of surface-bound WOCs. Herein, we report the successful immobilization of underivatized Ru(II)-based WOCs (Ru–Cat1 = [Ru(tpy) (bpy) (H 2 O)] 2+ (tpy = 2,2':6'2"–terpyridine and bpy = 2,2;-bipyridine) and Ru–Cat2 = [Ru(Mebimpy) (bpy) (H 2 O)] 2+ (Mebimpy = 2,6-bis(1-methylbenzimidazol-2-yl) pyridine)) and the Ru(II) polypyridyl chromophore Ru–C3 = [Ru(bpy) 3 ] 2+ onto a FTO plasma-grafted poly(acrylic acid) surface (PAA|FTO). Various characterization techniques such as attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, and cyclic voltammetry measurements provide evidence for the plasma-induced grafted PAA|FTO film and immobilization. Surface stability and electrocatalytic properties of these new hybrid composite films upon cycling were investigated at different pH values. Immobilized Ru–Cat1 and Ru–Cat2 onto PAA|FTO displayed pH-dependent (RuIII/RuII) couples and onset potentials indicative of PCET (proton-coupled electron transfer) reactions. Based on cyclic voltammetry results and spectroscopic monitoring, the immobilized WOCs Ru–Cat1 and Ru–Cat2 exhibited a higher surface stability in neutral aqueous solutions relative to Ru–C3 upon electrochemical oxidation. Furthermore, we attribute the surface PCET and stability to the presence of a water ligand in the coordination sphere of immobilized Ru–Cat1 and Ru–Cat2 which can H-bond with negatively charged carboxylate groups of the cross-linked PAA brushes. Our findings demonstrate that the plasma-grafted polymeric network onto FTO offers a versatile platform to directly anchor unmodified homogeneous WOCs or chromophores for potential applications in solar-to-fuel energy conversion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗