Scholarly Works, Chemistry

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Hydrothermally Assisted Conversion of Switchgrass into Hard Carbon as Anode Materials for Sodium-Ion Batteries
Li, Yilin; Xia, Dawei; Tao, Lei; Xu, Zhiyuan; Yu, Dajun; Jin, Qing; Lin, Feng; Huang, Haibo (American Chemical Society, 2024-05-23)
Sodium-ion batteries (SIBs) are emerging as a viable alternative to lithium-ion batteries, reducing the reliance on scarce transition metals. Converting agricultural biomass into SIB anodes can remarkably enhance sustainability in both the agriculture and battery industries. However, the complex and costly synthesis and unsatisfactory electrochemical performance of biomass-derived hard carbon have hindered its further development. Herein, we employed a hydrothermally assisted carbonization process that converts switchgrass to battery-grade hard carbon capable of efficient Na-ion storage. The hydrothermal pretreatment effectively removed hemicellulose and impurities (e.g., lipids and ashes), creating thermally stable precursors suitable to produce hard carbon via carbonization. The elimination of hemicellulose and impurities contributes to a reduced surface area and lower oxygen content. With the modifications, the initial Coulombic efficiency (ICE) and cycling stability are improved concurrently. The optimized hard carbon showcased a high reversible specific capacity of 313.4 mAh g(-1) at 100 mA g(-1), a commendable ICE of 84.8%, and excellent cycling stability with a capacity retention of 308.4 mAh g(-1) after 100 cycles. In short, this research introduces a cost-effective method for producing anode materials for SIBs and highlights a sustainable pathway for biomass utilization, underscoring mutual benefits for the energy and agricultural sectors.
Mechanistic Diversity in the Hydrolysis of Sarin by Single Transition-Metal Atoms on MOF-808
Fossum, Carl; Troya, Diego (American Chemical Society, 2024-05-24)
Zr-based metal-organic frameworks (Zr-MOFs) are one of the most promising materials for the decomposition of chemical warfare nerve agents. We present a study of the hydrolysis reaction mechanism of nerve agent sarin catalyzed by Zn(II) and Ti(IV) single atoms on the Zr-MOF MOF-808. We reveal that upon binding of the nerve agent to the catalyst, conformational isomerism leads to a great diversity of hydrolysis reaction mechanisms. Each mechanism follows an addition-elimination sequence but differs markedly in the way the elimination step is accomplished and its energetics. Moreover, while most of the prior work has focused on the HF elimination channel, this work shows that the addition-elimination steps can also lead to isopropanol formation through barriers comparable to those of the HF channel. Additional insight is achieved by high-level electronic structure calculations, including coupled-cluster theory, which allow us to benchmark more efficient DFT techniques commonly used in mechanistic studies of catalytic processes involving transition-metal atoms. Overall, this work reveals new reaction pathways for nerve-agent hydrolysis with lower-lying transition-state energies than previously reported, highlighting the importance of conformational sampling in mechanistic studies of catalytic processes.
Solvent-Mediated, Reversible Ternary Graphite Intercalation Compounds for Extreme-Condition Li-Ion Batteries
Tao, Lei; Xia, Dawei; Sittisomwong, Poom; Zhang, Hanrui; Lai, Jianwei; Hwang, Sooyeon; Li, Tianyi; Ma, Bingyuan; Hu, Anyang; Min, Jungki; Hou, Dong; Shah, Sameep Rajubhai; Zhao, Kejie; Yang, Guang; Zhou, Hua; Li, Luxi; Bai, Peng; Shi, Feifei; Lin, Feng (American Chemical Society, 2024-06-07)
Traditional Li-ion intercalation chemistry into graphite anodes exclusively utilizes the cointercalation-free or cointercalation mechanism. The latter mechanism is based on ternary graphite intercalation compounds (t-GICs), where glyme solvents were explored and proved to deliver unsatisfactory cyclability in LIBs. Herein, we report a novel intercalation mechanism, that is, in situ synthesis of t-GIC in the tetrahydrofuran (THF) electrolyte via a spontaneous, controllable reaction between binary-GIC (b-GIC) and free THF molecules during initial graphite lithiation. The spontaneous transformation from b-GIC to t-GIC, which is different from conventional cointercalation chemistry, is characterized and quantified via operando synchrotron X-ray and electrochemical analyses. The resulting t-GIC chemistry obviates the necessity for complete Li-ion desolvation, facilitating rapid kinetics and synchronous charge/discharge of graphite particles, even under high current densities. Consequently, the graphite anode demonstrates unprecedented fast charging (1 min), dendrite-free low-temperature performance, and ultralong lifetimes exceeding 10 000 cycles. Full cells coupled with a layered cathode display remarkable cycling stability upon a 15 min charging and excellent rate capability even at -40 degrees C. Furthermore, our chemical strategies are shown to extend beyond Li-ion batteries to encompass Na-ion and K-ion batteries, underscoring their broad applicability. Our work contributes to the advancement of graphite intercalation chemistry and presents a low-cost, adaptable approach for achieving fast-charging and low-temperature batteries.
Physically Motivated Improvements of Variational Quantum Eigensolvers
Vaquero-Sabater, Nonia; Carreras, Abel; Orus, Roman; Mayhall, Nicholas J.; Casanova, David (American Chemical Society, 2024-06-10)
The adaptive derivative-assembled pseudo-Trotter variational quantum eigensolver (ADAPT-VQE) has emerged as a pivotal promising approach for electronic structure challenges in quantum chemistry with noisy quantum devices. Nevertheless, to surmount existing technological constraints, this study endeavors to enhance ADAPT-VQE's efficacy. Leveraging insights from the electronic structure theory, we concentrate on optimizing state preparation without added computational burden and guiding ansatz expansion to yield more concise wave functions with expedited convergence toward exact solutions. These advancements culminate in shallower circuits and, as demonstrated, reduced measurement requirements. This research delineates these enhancements and assesses their performance across mono, di, and tridimensional arrangements of H-4 models, as well as in the water molecule. Ultimately, this work attests to the viability of physically motivated strategies in fortifying ADAPT-VQE's efficiency, marking a significant stride in quantum chemistry simulations.
Polysaccharide-based H₂S donors: Thiol-ene functionalization of amylopectin with H₂S-releasing N-thiocarboxyanhydrides
Chinn, Abigail F.; Williams, Noah R.; Miller, Kevin M.; Matson, John B. (Wiley, 2024-09-15)
Polymeric donors of gasotransmitters, gaseous signaling molecules such as hydrogen sulfide, nitric oxide, and carbon monoxide, hold potential for localized and extended delivery of these reactive gases. Examples of gasotransmitter donors based on polysaccharides are limited despite the availability and generally low toxicity of this broad class of polymers. In this work, we sought to create a polysaccharide H2S donor by covalently attaching N-thiocarboxyanhydrides (NTAs) to amylopectin, the major component of starch. To accomplish this, we added an allyl group to an NTA, which can spontaneously hydrolyze to release carbonyl sulfide and ultimately H2S via the ubiquitous enzyme carbonic anhydrase, and then coupled it to thiol-functionalized amylopectin of three different molecular weights (MWs) through thiol-ene "click" photochemistry. We also varied the degree of substitution (DS) of the NTA along the amylopectin backbone. H2S release studies on the six samples, termed amyl-NTAs, with variable MWs (three) and DS values (two), revealed that lower MW and higher DS led to faster release. Finally, dynamic light scattering experiments suggested that aggregation increased with MW, which may also have affected H2S release rates. Collectively, these studies present a new synthetic method to produce polysaccharide H2S donors for applications in the biomedical field.
Regioselective Annulation of 6-Carboxy-Substituted Pyrones as a Two-Carbon Unit in Formal [4+2] Cycloaddition Reactions
Kohanov, Zachary A.; Shuvo, Suzzudul Islam; Lowell, Andrew N. (American Chemical Society, 2024-06-13)
Heterocycles serve as a critical motif in chemistry, but despite being present in more than 85% of pharmaceuticals, there are limited methods for their construction. Here, we describe the incorporation of intact pyrone (2H-pyran-2-one) into larger ring systems via annulation. In a formal [4 + 2] cycloaddition, the pyrone regioselectively accepts a benzylic anion as a nucleophile in a conjugate addition fashion, with the subsequent pyrone-derived enolate attaching to a pendant ester on the initial nucleophile. Subsequent base-driven enolate formation and elimination establish aromaticity of the newly formed ring. After optimization of this process using an NMR-based assessment to overcome solubility and separation challenges, the reaction was successfully applied to a library of 6-ester and -amide-substituted pyrones and using a phenyl ester and other substituted sulfoxides. This technology enables the incorporation of intact pyrone rings into more complex systems, such as for the total synthesis of the natural product thermorubin.
Discovery of Potent, Orally Bioavailable Sphingosine-1-Phosphate Transporter (Spns2) Inhibitors
Foster, Daniel J.; Dunnavant, Kyle; Shrader, Christopher W.; LoPresti, Marion; Seay, Sarah; Kharel, Yugesh; Brown, Anne M.; Huang, Tao; Lynch, Kevin R.; Santos, Webster L. (American Chemical Society, 2024-07-02)
Targeting the S1P pathway has resulted in the development of S1P1 receptor modulators for the treatment of multiple sclerosis and ulcerative colitis. We hypothesize that targeting an upstream node of the S1P pathway may provide an improved adverse event profile. In this report, we performed a structure-activity relationship study focusing on the benzoxazole scaffold in SLB1122168, which lead to the discovery of 11i (SLF80821178) as a potent inhibitor of S1P release from HeLa cells (IC50: 51 +/- 3 nM). Administration of SLF80821178 to mice induced similar to 50% reduction in circulating lymphocyte counts, recapitulating the lymphopenia characteristic of Spns2 null animals. Molecular modeling studies suggest that SLF80821178 binds Spns2 in its occluded inward-facing state and forms hydrogen bonds with Asn112 and Ser211 and pi stacking with Phe234. Taken together, SLF80821178 can serve as a scaffold for future inhibitor development and represents a chemical tool to study the therapeutic implication of inhibiting Spns2.
Chemo-, Regio-, and Stereoselective cis-Hydroboration of 1,3-Enynes: Copper-Catalyzed Access to (Z,Z)- and (Z,E)-2-Boryl-1,3-dienes
Buchbinder, Nicklas W.; Nguyen, Long H.; Beck, Owen N.; Bage, Andrew D.; Slebodnick, Carla; Santos, Webster L. (American Chemical Society, 2024-07-17)
A copper-catalyzed alkyne-selective hydroboration of 1,3-enynes is disclosed, providing access to the previously elusive 2-boryl-1,3-dienes. Using CuOAc, Xantphos, and HBpin, Bpin was installed on the internal carbon of a series of symmetric and nonsymmetric 1,3-enynes, affording products with excellent Z:E selectivity. The utility of the 2-boryl-1,3-diene products was demonstrated by transformation to useful functional groups.
A Green, Fire-Retarding Ether Solvent for Sustainable High-Voltage Li-Ion Batteries at Standard Salt Concentration
Xia, Dawei; Tao, Lei; Hou, Dong; Hu, Anyang; Sainio, Sami; Nordlund, Dennis; Sun, Chengjun; Xiao, Xianghui; Li, Luxi; Huang, Haibo; Lin, Feng (Wiley-V C H Verlag, 2024-10-01)
Lithium-ion batteries (LIBs) are increasingly encouraged to enhance their environmental friendliness and safety while maintaining optimal energy density and cost-effectiveness. Although various electrolytes using greener and safer glyme solvents have been reported, the low charge voltage (usually lower than 4.0 V vs Li/Li+) restricts the energy density of LIBs. Herein, tetraglyme, a lesstoxic, non-volatile, and non-flammable ether solvent, is exploited to build safer and greener LIBs. It is demonstrated that ether electrolytes, at a standard salt concentration (1 m), can be reversibly cycled to 4.5 V vs Li/Li+. Anchored with Boron-rich cathode-electrolyte interphase (CEI) and mitigated current collector corrosion, the LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode delivers competitive cyclability versus commercial carbonate electrolytes when charged to 4.5 V. Synchrotron spectroscopic and imaging analyses show that the tetraglyme electrolyte can sufficiently suppress the overcharge behavior associated with the high-voltage electrolyte decomposition, which is advantageous over previously reported glyme electrolytes. The new electrolyte also enables minimal transition metal dissolution and deposition. NMC811||hard carbon full cell delivers excellent cycling stability at C/3 with a high average Coulombic efficiency of 99.77%. This work reports an oxidation-resilient tetraglyme electrolyte with record-high 4.5 V stability and enlightens further applications of glyme solvents for sustainable LIBs by designing Boron-rich interphases.
Kinetics of Calcite Nucleation onto Sulfated Chitosan Derivatives and Implications for Water-Polysaccharide Interactions during Crystallization of Sparingly Soluble Salts
Knight, Brenna M.; Mondal, Ronnie; Han, Nizhou; Pietra, Nicholas F.; Hall, Brady A.; Edgar, Kevin J.; Welborn, Valerie Vaissier; Madsen, Louis A.; De Yoreo, James J.; Dove, Patricia M. (American Chemical Society, 2024-07-11)
Anionic macromolecules are found at sites of CaCO3 biomineralization in diverse organisms, but their roles in crystallization are not well-understood. We prepared a series of sulfated chitosan derivatives with varied positions and degrees of sulfation, DS(SO3-), and measured calcite nucleation rate onto these materials. Fitting the classical nucleation theory model to the kinetic data reveals the interfacial free energy of the calcite-polysaccharide-solution system, gamma(net), is lowest for nonsulfated controls and increases with DS(SO3-). The kinetic prefactor also increases with DS(SO3-). Simulations of Ca2+-H2O-chitosan systems show greater water structuring around sulfate groups compared to uncharged substituents, independent of sulfate location. Ca2+-SO3- interactions are solvent-separated by distances that are inversely correlated with DS(SO3-) of the polysaccharide. The simulations also predict SO3- and NH3+ groups affect the solvation waters and HCO3- ions associated with Ca2+. Integrating the experimental and computational evidence suggests sulfate groups influence nucleation by increasing the difficulty of displacing near-surface water, thereby increasing gamma(net). By correlating gamma(net) and net charge per monosaccharide for diverse polysaccharides, we suggest the solvent-separated interactions of functional groups with Ca2+ influence thermodynamic and kinetic components to crystallization by similar solvent-dominated processes. The findings reiterate the importance of establishing water structure and properties at macromolecule-solution interfaces.
Revisiting Artifacts of Kohn-Sham Density Functionals for Biosimulation
Slattery, Samuel A.; Yon, Jaden C.; Valeev, Edward F. (American Chemical Society, 2024-07-31)
We revisit the problem of unphysical charge density delocalization/fractionalization induced by the self-interaction error of common approximate Kohn-Sham (KS) density functional theory functionals on simulation of small to medium-sized proteins in a vacuum. Aside from producing unphysical electron densities and total energies, the vanishing of the HOMO-LUMO gap associated with the unphysical charge delocalization leads to an unphysical low-energy spectrum and catastrophic failure of most popular solvers for the KS self-consistent field (SCF) problem. We apply a robust quasi-Newton SCF solver [] to obtain solutions for some of these difficult cases. The anatomy of the charge delocalization is revealed by the natural deformation orbitals obtained from the density matrix difference between the Hartree-Fock and KS solutions; the charge delocalization not only can occur between charged fragments (such as in zwitterionic polypeptides) but also involves neutral fragments. The vanishing-gap phenomenon and troublesome SCF convergence are both attributed to the unphysical KS Fock operator eigenspectra of molecular fragments (e.g., amino acids or their side chains). Analysis of amino acid pairs suggests that the unphysical charge delocalization can be partially ameliorated by the use of some range-separated hybrid functionals but not by semilocal or standard hybrid functionals. Last, we demonstrate that solutions without the unphysical charge delocalization can be located even for semilocal KS functionals highly prone to such defects, but such solutions have non-Aufbau character and are unstable with respect to mixing of the non-overlapping "frontier" orbitals. Caution should be exercised when unexpectedly small (or vanishing) HOMO-LUMO gaps and atypical SCF convergence patterns (e.g., oscillatory) are observed in KS DFT simulations in any context (bio or otherwise).
Design, synthesis and biological evaluation of glucose metabolism inhibitors as anticancer agents
Cheng, Yao; Jones, John Patrick; Yu, Tsz Tin; Olzomer, Ellen M.; Su, Jacky; Katen, Alice; Black, David StC; Hart-Smith, Gene; Childress, Elizabeth S.; Wilkins, Marc R.; Mateos, Isabel A.; Santos, Webster L.; Hoehn, Kyle L.; Byrne, Frances L.; Kumar, Naresh (Academic Press-Elsevier, 2024-10-01)
Compared to normal cells, tumour cells exhibit an upregulation of glucose transporters and an increased rate of glycolytic activity. In previous research, we successfully identified a promising hit compound BH10 through a rigorous screening process, which demonstrates a potent capacity for inhibiting cancer cell proliferation by targeting glucose metabolism. In the current study, we identify Kelch-like ECH-associated protein 1 (Keap1) as a potential protein target of BH10 via avidin pull-down assays with biotinylated-BH10. Subsequently, we present a comprehensive analysis of a series of BH10 analogues characterized by the incorporation of a naphthoimidazole scaffold and the introduction of a triazole ring with diverse terminal functional groups. Notably, compound 4d has emerged as the most potent candidate, exhibiting better anti-cancer activities against HEC1A cancer cells with an IC50 of 2.60 mu M, an extended biological half-life, and an improved pharmacokinetic profile (compared to BH10) in mice.
Simulation of Vibrational Circular Dichroism Spectra Using Second-Order Møller-Plesset Perturbation Theory and Configuration Interaction Doubles
Shumberger, Brendan M.; Crawford, T. Daniel (American Chemical Society, 2024-08-13)
We present the first single-reference calculations of the atomic axial tensors (AATs) with wave function-based methods including dynamic electron correlation effects using second-order M & oslash;ller-Plesset perturbation theory (MP2) and configuration interaction doubles (CID). Our implementation involves computing the overlap of numerical derivatives of the correlated wave functions with respect to both nuclear displacement coordinates and the external magnetic field. Out test set included three small molecules, including the axially chiral hydrogen molecule dimer and (P)-hydrogen peroxide, and the achiral H2O. For our molecular test set, we observed deviations of the AATs for MP2 and CID from that of the Hartree-Fock (HF) method upward of 49%, varying with the choice of basis set. For (P)-hydrogen peroxide, electron correlation effects on the vibrational circular dichroism (VCD) rotatory strengths and corresponding spectra were particularly significant, with maximum deviations of the rotatory strengths of 62 and 49% for MP2 and CID, respectively, using our largest basis set. The inclusion of dynamic electron correlation to the computation of the AATs can have a significant impact on the resulting rotatory strengths and VCD spectra.
Beneficial effects of MGL-3196 and BAM15 combination in a mouse model of fatty liver disease
Zhou, Mingyan; Li, Catherine; Byrne, Frances L.; Vancuylenburg, Calum S.; Olzomer, Ellen M.; Hargreaves, Adam; Wu, Lindsay E.; Shackel, Nicholas A.; Santos, Webster L.; Hoehn, Kyle L. (Wiley, 2024-10-01)
Background and Aim: Metabolic dysfunction-associated steatohepatitis (MASH) is a metabolic disorder with limited treatment options. The thyroid hormone receptor (THR)-beta agonist resmetirom/MGL-3196 (MGL) increases liver fat oxidation and has been approved for treating adult MASH. However, over 60% of patients receiving MGL treatment do not achieve MASH resolution. Therefore, we investigated the potential for combination therapy of MGL with the mitochondrial uncoupler BAM15 to improve fatty liver disease outcomes in the GAN mouse model of MASH. Methods: C57BL/6J male mice were fed GAN diet for 38 weeks before stratification and randomization to treatments including MGL, BAM15, MGL + BAM15, or no drug control for 8 weeks. Treatments were admixed in diet and mice were pair-fed to control for drug intake. Treatment effectiveness was assessed by body weight, body composition, energy expenditure, glucose tolerance, tissue lipid content, and histological analyses. Results: MGL + BAM15 treatment resulted in better efficacy versus GAN control mice than either monotherapy in the context of energy expenditure, liver fat loss, glucose control, and fatty liver disease activity score. Improvements in ALT, liver mass, and plasma cholesterol were primarily driven by MGL, while improvements in body fat were primarily driven by BAM15. No treatments altered liver fibrosis. Conclusions: MGL + BAM15 treatment had overall better efficacy to improve metabolic outcomes in mice fed GAN diet than either monotherapy alone. These data warrant further investigation into combination therapies of THR-beta agonists and mitochondrial uncouplers for the potential treatment of disorders related to fatty liver, obesity, and insulin resistance.
Deficiency of the sphingosine-1-phosphate (S1P) transporter Mfsd2b protects the heart against hypertension-induced cardiac remodeling by suppressing the L-type-Ca2+ channel
Duse, Dragos Andrei; Schroeder, Nathalie Hannelore; Srivastava, Tanu; Benkhoff, Marcel; Vogt, Jens; Nowak, Melissa Kim; Funk, Florian; Semleit, Nina; Wollnitzke, Philipp; Erkens, Ralf; Koetter, Sebastian; Meuth, Sven Guenther; Keul, Petra; Santos, Webster; Polzin, Amin; Kelm, Malte; Krueger, Martina; Schmitt, Joachim; Levkau, Bodo (Springer, 2024-10-01)
The erythrocyte S1P transporter Mfsd2b is also expressed in the heart. We hypothesized that S1P transport by Mfsd2b is involved in cardiac function. Hypertension-induced cardiac remodeling was induced by 4-weeks Angiotensin II (AngII) administration and assessed by echocardiography. Ca2+ transients and sarcomere shortening were examined in adult cardiomyocytes (ACM) from Mfsd2b(+/+) and Mfsd2b(-/-) mice. Tension and force development were measured in skinned cardiac fibers. Myocardial gene expression was determined by real-time PCR, Protein Phosphatase 2A (PP2A) by enzymatic assay, and S1P by LC/MS, respectively. Msfd2b was expressed in the murine and human heart, and its deficiency led to higher cardiac S1P. Mfsd2b(-/-) mice had regular basal cardiac function but were protected against AngII-induced deterioration of left-ventricular function as evidenced by similar to 30% better stroke volume and cardiac index, and preserved ejection fraction despite similar increases in blood pressure. Mfsd2b(-/-) ACM exhibited attenuated Ca2+ mobilization in response to isoprenaline whereas contractility was unchanged. Mfsd2b(-/-) ACM showed no changes in proteins responsible for Ca2+ homeostasis, and skinned cardiac fibers exhibited reduced passive tension generation with preserved contractility. Verapamil abolished the differences in Ca2+ mobilization between Mfsd2b(+/+) and Mfsd2b(-/-) ACM suggesting that S1P inhibits L-type-Ca2+ channels (LTCC). In agreement, intracellular S1P activated the inhibitory LTCC phosphatase PP2A in ACM and PP2A activity was increased in Mfsd2b(-/-) hearts. We suggest that myocardial S1P protects from hypertension-induced left-ventricular remodeling by inhibiting LTCC through PP2A activation. Pharmacologic inhibition of Mfsd2b may thus offer a novel approach to heart failure.
Ethyl cellulose-block-poly(benzyl glutamate) block copolymer compatibilizers for ethyl cellulose/poly(ethylene terephthalate) blends
Chinn, Abigail F.; Trindade Coutinho, Isabela; Kethireddy, Saipranavi Reddy; Williams, Noah R.; Knott, Kenneth M.; Moore, Robert B.; Matson, John B. (Royal Society Chemistry, 2024-08-27)
Blends of petroleum-based polymers with bio-sourced polymers are an alternative to polymers derived from non-renewable resources. However, polymer blends are usually immiscible, and a compatibilizer, often a block copolymer, is required to improve mixing. In this work, we synthesized a block copolymer of ethyl cellulose (ECel) and poly(benzyl glutamate), termed ECel-block-poly(BG), and we applied it as a compatibilizer for ECel/poly(ethylene terephthalate) (ECel/PET) blends. To synthesize this block copolymer, two ECel-NH2 macroinitiators were evaluated for ring-opening polymerization of benzyl glutamate-N-thiocarboxyanhydride (BG-NTA), one with the amine directly attached to the ECel reducing chain end, and the other with a short PEG linker between ECel and the amine initiator. The PEG-containing macroinitiator led to the synthesis of a block copolymer that was unimodal by size-exclusion chromatography (SEC) while the other initiator led to uncontrolled homopolymerization of BG-NTA, presumably due to steric hindrance near the primary amine. A series of solvent studies revealed that polymerization of BG-NTA in CH2Cl2 was the best system for obtaining the ECel-block-poly(BG) block copolymer, achieving 95% conversion based on H-1 NMR spectroscopy. The success of chain extension and molecular weight analysis were evaluated using SEC with multi-angle light scattering (SEC-MALS). Blends composed of 70% ECel and 30% PET with different weight percentages (wt%) of block copolymer compatibilizer were made via solvent casting from hexafluoroisopropanol. Phase contrast optical microscopy and small-angle laser light scattering were used to probe the effectiveness of the ECel-block-poly(BG) block copolymer as a compatibilizer (5-30 wt%) for the 70/30 ECel/PET blends. A decrease in average domain size from 15 +/- 4 mu m in the base blend (without compatibilizer) to 2 +/- 1 mu m in the blend containing 30 wt% ECel-block-poly(BG) indicated successful compatibilization of the blend.
Macromorphological Control of Zr-Based Metal-Organic Frameworks for Hydrolysis of a Nerve Agent Simulant
Gibbons, Bradley; Johnson, Eric M.; Javed, Mohammad Khurram; Yang, Xiaozhou; Morris, Amanda J. (American Chemical Society, 2024-09-18)
Zirconium-based metal-organic frameworks (MOFs) have become one of the most promising materials for the adsorption and destruction of chemical warfare agents. While numerous studies have shown differences in reactivity based on MOF topology and postsynthetic modification, the understanding of how modifying MOF macromorphology is less understood. MOF xerogels demonstrate modified defect levels and larger porosity, which increase the number of and access to potential active sites. Indeed, UiO-66 and NU-901 xerogels display reaction rates 2 and 3 times higher, respectively, for the hydrolysis of DMNP relative to their powder morphologies. Upon recycling, MOF-808 xerogel outperforms MOF-808 powder, previously noted as the fastest Zr6 MOF for hydrolysis of organophosphate nerve agents. The increase in reactivity is largely driven by a higher external surface area and the introduction of mesoporosity to previously microporous materials.
Customizing STEM organogels using PET-RAFT polymerization
Bowman, Zaya; Baker, Jared G.; Hughes, Madeleine J.; Nguyen, Jessica D.; Garcia, Mathew; Tamrat, Nahome; Worch, Joshua C.; Figg, C. Adrian (Royal Society Chemistry, 2024-10-01)
Photoinduced electron/energy transfer (PET) reversible addition-fragmentation chain transfer (RAFT) polymerization results in more uniform polymer networks compared to networks synthesized by thermally initiated RAFT polymerizations. However, how PET-RAFT polymerizations affect molecular weight control and physical properties during parent-to-daughter block copolymer network synthesis is unclear. Herein, we synthesized a structurally tailored and engineered macromolecular (STEM) organogel composed of poly(methyl acrylate) and a degradable crosslinker. Chain extensions on the STEM organogel were performed using PET-RAFT polymerization of either methyl acrylate (MA) or N,N-dimethylacrylamide (DMA) with or without additional crosslinker. We found that physical properties were dependent on monomer composition and crosslinking. The swelling ratios of the diblock networks were similar in DMAc. Conversely, swelling ratios in water increased by 430% for networks extended with MA and 5200% for networks extended with DMA compared to the parent organogels. Rheological analysis showed a tunable modulus from 1000-4000 Pa. However, size exclusion chromatography analysis of the degraded gels revealed that the PET-RAFT polymerization chain extension yielded disperse block copolymers with poor control over the molecular weight. These results indicate that PET-RAFT polymerizations can be used to expand organogel networks to block copolymer networks to modulate physical properties, but control over the chain extension polymerization is lost. Looking forward, this report points to opportunities to gain control over PET-RAFT block copolymer network synthesis via secondary reversible deactivation pathways. PET-RAFT polymerization was used to modify STEM organogels, while degradable linkers enabled the characterization of the resulting block copolymers.
Electrospun Lithium Porous Nanosorbent Fibers for Enhanced Lithium Adsorption and Sustainable Applications
Pan, Yanan; Zhang, Yue; Thompson, Connor; Liu, Guoliang; Zhang, Wencai (American Chemical Society, 2024-09-30)
Electrospun nanosorbent fibers specifically designed for efficient lithium extraction were developed, exhibiting superior physicochemical properties. These fibers were fabricated using a polyacrylonitrile/dimethylformamide matrix, with viscosity and dynamic mechanical analysis showing that optimal interactions were achieved at lower contents of layered double hydroxide. This meticulous adjustment in formulation led to the creation of lithium porous nanosorbent fibers (Li-PNFs-1). Li-PNFs-1 exhibited outstanding mechanical attributes, including a yield stress of 0.09 MPa, a tensile strength of 2.48 MPa, and an elongation at a break of 19.7%. Additionally, they demonstrated pronounced hydrophilicity and hierarchical porous architecture, which greatly favor rapid wetting kinetics and lithium adsorption. Morphologically, they exhibited uniform smoothness with a diameter averaging 546 nm, indicative of orderly crystalline growth and a dense molecular arrangement. X-ray photoelectron spectroscopy and density functional theory using Cambridge Serial Total Energy Package revealed modifications in the spatial and electronic configurations of polyacrylonitrile due to hydrogen bonding, facilitating lithium adsorption capacity up to 13.45 mg/g under optimal conditions. Besides, kinetics and isotherm showed rapid equilibrium within 60 min and confirmed the chemical and selective nature of Li+ uptake. These fibers demonstrated consistent adsorption performance across multiple cycles, highlighting their potential for sustainable use in industrial applications.
Restricted Open-Shell Cluster Mean-Field theory for Strongly Correlated Systems
Bachhar, Arnab; Mayhall, Nicholas J. (American Chemical Society, 2024-10-07)
The cluster-based Mean Field method (cMF) and it is second order perturbative correction was introduced by Jimenez-Hoyos and Scuseria to reduce the cost of modeling strongly correlated systems by dividing an active space up into small clusters, which are individually solved in the mean-field presence of each other. In that work, clusters with unpaired electrons are treated by allowing the alpha and beta orbitals to spin polarize. While that provided significant energetic stabilization, the resulting cMF wave function was spin-contaminated, making it difficult to use as a reference state for spin-pure post-cMF methods. In this work, we propose the Restricted Open-shell cMF (RO-cMF) method, extending the cMF approach to systems with open-shell clusters, while not permitting spin-polarization. While the resulting RO-cMF energies are necessarily higher in energy than the unrestricted orbital cMF, the new RO-cMF provides a simple reference state for post-cMF methods that recover the missing intercluster correlations. We provide a detailed explanation of the method, and report demonstrative calculations of exchange coupling constants for three systems: a di-iron complex, a dichromium complex, and a dimerized organic radical. We also report the first perturbatively corrected RO-cMF-PT2 results as well.

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