Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “polymerization”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Polymeric and ceramic silicon-based coatings – a review

Silicon-based polymers are outstanding materials for coating applications. These compounds have excellent properties, such as strong adhesion to most substrates, and high chemical, thermal and UV resistance. Additionally, they can be converted into ceramic materials (polymer-derived ceramics) by a heat treatment and, in some cases, by chemical reactions or radiation. Hence, ceramic coatings can be obtained after deposition of the polymers by simple lacquer techniques. The properties and composition of polymeric and ceramic coatings can be changed by tailoring the chemical structure of the precursors or by the addition of fillers. This enables the preparation of coatings with a great variety of properties for different applications. In this review paper, the main aspects of the use of silicon polymers for coatings are elucidated. The advantages and disadvantages of these materials, and the processing methods developed are discussed. Lastly, a summary of the applications and the prospects for future research are presented.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structural correlations tailor conductive properties in polymerized ionic liquids

Polymerized ionic liquids (PolyILs) are enticing materials for applications in electrochemical devices spanning from fuel cells to capacitors and batteries. In principle, PolyILs have a competitive advantage over traditional electrolytes in being single ion conductors and thus enabling a transference number close to unity. Despite this perceived advantage, surprisingly low room temperature ionic conductivities measured in the lab raise an important fundamental question: how does the molecular structure mediate conductivity? Here, wide-angle X-ray scattering (WAXS), vibrational sum frequency generation (vSFG), and density functional theory (DFT) calculations were used to study the bulk and interfacial structure of PolyILs, while broad band dielectric spectroscopy (BDS) was used to probe corresponding dynamics and conductive properties for a series of the PolyIL samples with tunable chemistries and structures. Our results reveal that the size of the mobile anions has a tremendous impact on chain packing in PolyILs that wasn’t addressed previously. Larger mobile ions tend to create a well-packed structure, while smaller ions frustrate chain packing. The magnitude of these changes and level of structural heterogeneity are shown to depend on the chemical functionality and flexibility of studied PolyILs. Moreover, these experimental and computational results provide new insight into the correlation between conductivity and structure in PolyILs, suggesting that structural heterogeneity helps to reduce the activation energy for ionic conductivity in the glassy state.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Catalytic activation of ethylene C–H bonds on uniform d 8 Ir( I ) and Ni( II ) cations in zeolites: toward molecular level understanding of ethylene polymerization on heterogeneous catalysts

The homolytic activation of the strong C–H bonds in ethylene is demonstrated, for the first time, on d 8 Ir(I) and Ni(II) single atoms in the cationic positions of zeolites H-FAU and H-BEA under ambient conditions. The oxidative addition of C 2 H 4 to the metal center occurs with the formation of a d 6 metal vinyl hydride, explaining the initiation of the olefin-polymerization cycle on d 8 M(I/II) sites in the absence of pre-existing M–H bonds. Under mild reaction conditions (80–220 °C, 1 bar), the catalytic dimerization to butenes and dehydrogenative coupling of ethylene to butadiene occurs over these catalysts. 1-Butene is not converted to butadiene under the reaction conditions applied. Post-reaction characterization of the two materials reveals that the active metal cations remain site-isolated whereas deactivation occurs due to the formation of carbonaceous deposits on the zeolites. Here, our findings have significant implications for the molecular level understanding of ethylene conversion and the development of new ways to functionalize C–H bonds under mild conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Hydrophobic polymerized ionic liquids for trace metal solid phase extraction: thallium transfer from hydrochloric acid media

It is known that some neat room-temperature hydrophobic ionic liquids can extract metallic species from aqueous solutions. The unique properties of such organic media allow for the application of polymerization techniques to convert the liquid organic phase to a solid one. In this work, a pyrrolidinium-based ionic liquid and a corresponding polymer with bis(trifluoromethanesulfonyl)imide counter anion have been considered for optimization of thallium(III) migration in liquid-liquid and solid-liquid extraction systems. Neither trivalent indium nor monovalent thallium were absorbed by the polymer layer. A mathematical model to describe the mechanism of metal extraction in these systems has been developed. Thermodynamic parameters as adsorption enthalpy, entropy, and Gibbs energy have also been determined.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Block copolymers containing stable radical and fluorinated blocks with long-range ordered morphologies prepared by anionic polymerization

We report a facile synthetic approach to create stable radical block copolymers containing a secondary fluorinated block via anionic polymerization using a bulky, sterically hindered countercation composed of a sodium ion and di-benzo-18-crown-6 complex. The synthetic conditions described in this report allowed for controlled molecular weights and dispersity (<1.3) of both homopolymers: poly(2,2,6,6-tetramethyl-1-piperidinyloxy-methacrylate) (PTMA) and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) as well as their block copolymers (PTMA-b-PTFEMA). The stable radical concentration of the polymers was determined by electron spin resonance (ESR) and showed radical content above 70%. An analysis of the microphase morphologies in PTMA-b-PTFEMA thin films via atomic force microscopy (AFM) and grazing incidence small angle X-ray scattering (GISAXS) showed clear evidence of long-range ordering of lamellar and cylindrical morphologies with 32 and 36 nm spacing, respectively. The long-range ordering of the morphologies was developed with the aid of two separate neutral layers: PTMA-ran-PTFEMA-ran-poly(hydroxyl ethyl methacrylate) (PHEMA) and poly(isobutyl methacrylate) (PiBMA)-ran-PTFEMA-ran-PHEMA, which helped us corroborate, along with the Zisman method, the surface energy estimation of PTMA to be 30.1 mJ m -2 .

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

Concentration and velocity profiles in a polymeric lithium-ion battery electrolyte

Predictive knowledge of ion transport in electrolytes which bridges microscopic and macroscopic length scales is imperative to design new ion conductors and to simulate device performance. Here, we employed a novel approach combining operando X-ray photon correlation spectroscopy, X-ray absorption microscopy, continuum modelling, and molecular dynamics simulations to probe the ion transport in a baseline polymeric lithium-ion battery electrolyte. In a Li/PEO–LiTFSI/Li symmetric cell under polarization, we determined and rationalized microscopic properties including local electrolyte velocities and ion correlations and connected this insight to measured and simulated macroscopic ion concentration gradients. By relating our results across length scales, we suggest a fairly concentration-independent transference number of about 0.2. Our study shows the broad applicability of operando X-ray photon correlation spectroscopy to the understanding of dynamic phenomena.

25 ENERGY STORAGE↗
DOE OSTI2020

Multicolor polymeric carbon dots: synthesis, separation and polyamide-supported molecular fluorescence

Multicolor carbon dots (CDs) have been developed recently and demonstrate great potential in bio-imaging, sensing, and LEDs. However, the fluorescence mechanism of their tunable colors is still under debate, and efficient separation methods are still challenging. Herein, we synthesized multicolor polymeric CDs through solvothermal treatment of citric acid and urea in formamide. Automated reversed-phase column separation was used to achieve fractions with distinct colors, including blue, cyan, green, yellow, orange and red. This work explores the physicochemical properties and fluorescence origins of the red, green, and blue fractions in depth with combined experimental and computational methods. Three dominant fluorescence mechanism hypotheses were evaluated by comparing time-dependent density functional theory and molecular dynamics calculation results to measured characteristics. We find that blue fluorescence likely comes from embedded small molecules trapped in carbonaceous cages, while pyrene analogs are the most likely origin for emission at other wavelengths, especially in the red. Also important, upon interaction with live cells, different CD color fractions are trafficked to different sub-cellular locations. Super-resolution imaging shows that the blue CDs were found in a variety of organelles, such as mitochondria and lysosomes, while the red CDs were primarily localized in lysosomes. These findings significantly advance our understanding of the photoluminescence mechanism of multicolor CDs and help to guide future design and applications of these promising nanomaterials.

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

Biomass-Derived Polymeric Binders in Silicon Anodes for Battery Energy Storage Applications

The demand for portable electronic devices has increased rapidly during the past decade, and has driven a concordant growth in battery production. Since their development as a commercial energy storage solution in the 1990s, lithium-ion batteries (LIBs) have attracted significant attention in both science and industry due to their long cycle life, high energy density, low self-discharge rate, and high working voltage. Production of LIBs requires large amounts of a polymeric binder – commonly polyvinylidene difluoride (PVDF) – for processing and performance purposes. However, since this material is petrochemically-derived, it is far from “green” or sustainable. On the other hand, polymers and their building blocks are found widely throughout nature and can be renewably sourced from biomass at low cost; therefore, replacing PVDF with biomass-derived binders is a promising approach to reduce the environmental footprint of LIBs. Additionally, polymer binders play a critical role in next-generation battery performance. For instance, silicon (Si) is a promising high-capacity anode material for LIBs because of its high theoretical capacity (4200 mA h g –1 ), low working potential, and high abundance in Earth's crust. However, its huge volume change during charge/discharge tends to result in a shortened cycle life, since conventional binders interact only weakly with silicon's native surface and cannot maintain long-term integrity of the electrode. Naturally derived polymers have found better success in this role due to their high structural advantages. In this review, we summarize recent developments in silicon anode binders derived from various biomass sources, with a focus on polymer properties and their effect on battery performance. Further, we propose various perspectives based on our own assessment of these works, and provide a brief commentary on the future outlook of the field.

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

Lithium calix[4]arenes: structural studies and use in the ring opening polymerization of cyclic esters

We have structurally characterized a number of lithiated calix[4]arenes, where the bridge in the calix[4]arene is thia (–S–, L S H 4 ), sulfinyl (–SO–, L SO H 4 ), sulfonyl (–SO 2 –, L SO2 H 4 ), dimethyleneoxa (–CH 2 OCH 2 –, L COC H 4 ) or methylene (–CH 2 –, LH 4 ). In the case of L 4S H 4 , interaction with LiO t Bu led to the isolation of the complex [Li 8 (L 4S ) 2 (THF) 4 ]·5THF ( 1 ·5THF), whilst similar interaction of L 4SO H 4 led to the isolation of [Li 6 (L 4SO H) 2 (THF) 2 ]·5(THF) ( 2 ·5THF). Interestingly, the mixed sulfinyl/sulfonyl complexes [Li 8 (calix[4]arene(SO)(SO 2 )(SO 1.68 ) 2 ) 2 (THF) 6 ]·8(THF) ( 3 ·8THF) and [Li 5 Na(L SO/3SO2 H) 2 (THF) 5 ]·7.5(THF) ( 4 ·7.5(THF) have also been characterized. Interaction of LiO t Bu with L SO2 H 4 and L COC H 4 afforded [Li 5 L 4SO2 (OH)(THF) 4 ]·2THF ( 5 ·2THF) and [Li 6 (L COC ) 2 (HO t Bu) 2 ]·0.78THF·1.22hexane ( 6 ·0.78THF·1.22hexane), respectively. In the case of LH 4 , reaction with LiO t Bu in THF afforded a monoclinic polymorph [LH 2 Li 2 (thf)(OH 2 ) 2 ]·3THF ( 7 ·3THF) of a known triclinic form of the complex, whilst reaction of the de-butylated analogue of LH 4 , namely de-BuLH 4 , afforded a polymeric chain structure {[Li 5 (de-BuL)(OH)(NCMe) 3 ]·2MeCN} n ( 8 ·2MeCN). For comparative catalytic studies, the complex [Li 6 (L Pr ) 2 (H 2 O) 2 ]·hexane ( 9 hexane), where L Pr2 H 2 = 1,3-di- n -propyloxycalix[4]areneH 2 , was also prepared. The molecular crystal structures of 1–9 are reported, and their ability to act as catalysts for the ring opening (co-)/polymerization (ROP) of the cyclic esters ε-caprolactone, δ-valerolactone, and rac -lactide has been investigated. In most of the cases, complex 6 outperformed the other systems, allowing for higher conversions and/or greated polymer M n .

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

One-step fabrication of robust lithium ion battery separators by polymerization-induced phase separation

Conventional lithium ion battery separators are microporous polyolefin membranes that play a passive role in the electrochemical cell. Next generation separators should offer significant performance enhancements, while being fabricated through facile, low cost approaches with the ability to readily tune physicochemical properties. This study presents a single-step manufacturing technique based on UV-initiated polymerization-induced phase separation (PIPS), wherein microporous separators are fabricated from multifunctional monomers and ethylene carbonate (EC), which functions as both the pore-forming agent (porogen) and electrolyte component in the electrochemical cell. By controlling the ratio of the 1,4-butanediol diacrylate (BDDA) monomer to ethylene carbonate, monolithic microporous membranes are readily prepared with 25 μm thickness and pore sizes and porosities ranging from 6.8 to 22 nm and 15.4% to 38.5%, respectively. With 38.5% apparent porosity and an average pore size of 22 nm, the poly(1,4-butanediol diacrylate) (pBDDA) separator takes up 127% liquid electrolyte, resulting in an ionic conductivity of 1.98 mS cm –1 , which is greater than in conventional Celgard 2500. Lithium ion battery half cells consisting of LiNi 0.5 Mn 0.3 Co 0.2 O 2 cathodes and pBDDA separators were shown to undergo reversible charge/discharge cycling with an average discharge capacity of 142 mA h g –1 and a capacity retention of 98.4% over 100 cycles – comparable to cells using state-of-the-art separators. Moreover, similar discharge capacities were achieved in rate performance tests due to the high ionic conductivity and electrolyte uptake of the film. Finally, the pBDDA separators were shown to be thermally stable to 374 °C, lack low temperature thermal transitions that can compromise cell safety, and exhibit no thermal shrinkage up to 150 °C.

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

Heterogenous catalysis for oxygen tolerant photoredox atom transfer radical polymerization and small-molecule dehalogenation

Heterogeneous photocatalysts (PCs) have garnered attention for their sustainability and cost-effectiveness. Despite the existence of various types of these PCs, their synthesis often involves complex, multi-step procedures and laborious purification. Herein, we propose a simple method for attaching small-molecule photocatalytic species onto crosslinked 3-D polymer networks as insoluble scaffolds to create robust heterogeneous PCs. The highly swellable poly(ethylene glycol)-based ChemMatrix (CM) resin, known for its amphiphilic properties and high functional group loading, facilitated the covalent immobilization of the photoredox dye Eosin Y (EY), but also streamlined functionalization with Ir( III ) complexes. The resulting heterogeneous CM-EY demonstrated efficient photocatalytic performance in open-to-air dual photoredox catalysis of atom transfer radical polymerization (photo-ATRP) under green light. This was confirmed by the well-controlled synthesis of polymers with molecular masses ranging from 20 kDa to 300 kDa and low dispersities. Furthermore, CM-EY exhibited excellent photostability and recyclability over multiple cycles of ATRP. The heterogeneous catalysis of photo-ATRP provided high temporal control and enabled benign conditions for synthesizing protein-polymer hybrids (PPH). When combined with the initiator-modified CM (CM-BIB), CM-EY facilitated the solid-phase synthesis of homopolymers and block copolymers with recyclable performance. However, the coordinatively bound Ir@CM showed decreased catalytic activity and efficiency toward photoredox dehalogenation due to the leaching of active species during recycling. This study highlights the advantages of the covalent linking of catalysts to solid supports over non-covalent interactions, underscoring the potential of functionalized polymer resin as a promising scaffold. Such an approach offers customization and tunability, presenting opportunities for innovation in green chemistry.

Kapil, Kriti↗
DOE OSTI2025

Generating forces in confinement via polymerization

Understanding how to produce forces using biomolecular building blocks is essential for the development of adaptive synthetic cells and living materials. Here we ask whether a dynamic polymer system can generate deformation forces in soft shells by pure self-assembly, motivated by the fact that biological polymer networks like the cytoskeleton can exert forces, move objects, and deform membranes by simply growing, even in the absence of molecular motors. We address this question by investigating polymer force generation by varying the release rate, the structure, and the interactions of self-assembling monomers. First, we develop a toy computational model of polymerization in a soft elastic shell that reveals the emergence of spontaneous bundling which enhances shell deformation. We then extend our model to account more explicitly for monomer binding dynamics. We find that the rate at which monomers are released into the interior of the shell is a crucial parameter for achieving deformation through polymer growth. Lastly, we demonstrate that the introduction of multivalent particles that can join polymers can either improve or impede polymer performance, depending on the amount and on the structure of the multivalent particles. Our results provide guidance for the experimental realization of polymer systems that can perform work at the nanoscale, for example through rationally designed self-assembling proteins or nucleic acids.

Osmanović, Dino [University of California at Los A↗