Polymeric Intermediates Research Articles

Designing Heterodiatomic Carbon Hydrangea Superstructures via Machine Learning-Regulated Solvent-Precursor Interactions for Superior Zinc Storage.

Carbon superstructures with exquisite morphologies and functionalities show appealing prospects in energy realms, but the systematic tailoring of their microstructures remains a perplexing topic. Here, hydrangea-shaped heterodiatomic carbon superstructures (CHS) are designed using a solution phase manufacturing route, wherein machine learning workflow is applied to screen precursor-matched solvent for optimizing solvent-precursor interaction. Based on the established solubility parameter model and molecular growth kinetics simulation, ethanol as the optimal solvent stimulates thermodynamic solubilization and growth of polymeric intermediates to evoke CHS. Featured with surface-active motifs and consecutive charge transfer paths, CHS allows high accessibility of zincophilic sites and fast ion migration with low energy barriers. A anion-cation hybrid charge storage mechanism of CHS cathode is disclosed, which entails physical alternate uptake of Zn2+/CF3SO3 - ions at electroactive sites and chemical bipedal redox of Zn2+ ions with carbonyl/pyridine motifs. Such a beneficial electrochemistry contributes to all-round improvement in Zn-ion storage, involving excellent capacities (231 mAh g-1 at 0.5 A g-1; 132 mAh g-1 at 50 A g-1), high energy density (152Wh kg-1), and long-lasting cyclability (100000 cycles). This work expands the design versatilities of superstructure materials and will accelerate experimental procedures during carbon manufacturing through machine learning in the future.

Solvent-guided nanoarchitecturing of heterodiatomic carbon superstructures for high-performance zinc-ion hybrid capacitors

Designing well-structured carbon nanomaterials is crucial for promoting zinc-ion hybrid capacitors with high-kinetics and large-current Zn2+-storage viability. Herein we report the solvent-guided nanoarchitecturing of polyimide precursor to customize versatile heterodiatomic carbon superstructures (CS). Modulating the solvent-precursor interaction through a solubility parameter model and molecular dynamic simulation optimizes the thermodynamic solubilization (–2.14 eV) and growth kinetics (–9.22 eV) of polymeric intermediates with a minimum energy obstruction. The solvent-optimized CS exhibit well-defined spherical topology, ion-compatible pore channels and favorable dual-function motifs, affording more ample-exposed zincophilic platforms and high-speed ion transport routes. As a consequence, the assembled Zn||CS hybrid capacitor activates superior electrochemical activity and durability, including superior rate capacities (240 mAh g−1 at 0.5 A g−1, 108 mAh g−1 at 100 A g−1), high energy density (145 Wh kg−1) and ultralong lifespan (300,000 cycles at 50 A g−1). Marriage of experimental studies and theoretical calculations unravel the alternate storage of opposite charges in CS cathode, which involves high-kinetics physical Zn2+/CF3SO3− uptake at zincophilic sites and chemical redox of Zn2+ ions with carbonyl/pyridine motifs to initiate O−Zn−N bonds. Molecular dynamics simulations demonstrate that diffusion kinetics of Zn2+ ions is greatly facilitated by > 10 Å micropores with low energy barriers, but is blocked by < 7 Å micropores. This work provides new insights into the structural engineering of carbon superstructures for advanced energy storage.

In situ organic Fenton-like catalysis triggered by anodic polymeric intermediates for electrochemical water purification

Organic Fenton-like catalysis has been recently developed for water purification, but redox-active compounds have to be ex situ added as oxidant activators, causing secondary pollution problem. Electrochemical oxidation is widely used for pollutant degradation, but suffers from severe electrode fouling caused by high-resistance polymeric intermediates. Herein, we develop an in situ organic Fenton-like catalysis by using the redox-active polymeric intermediates, e.g., benzoquinone, hydroquinone, and quinhydrone, generated in electrochemical pollutant oxidation as H2O2 activators. By taking phenol as a target pollutant, we demonstrate that the in situ organic Fenton-like catalysis not only improves pollutant degradation, but also refreshes working electrode with a better catalytic stability. Both 1O2 nonradical and ·OH radical are generated in the anodic phenol conversion in the in situ organic Fenton-like catalysis. Our findings might provide a new opportunity to develop a simple, efficient, and cost-effective strategy for electrochemical water purification.

New polymeric adsorbent materials used for removal of phenolic derivatives from wastewaters

Abstract Phenolic compounds are produced in thermal cracking processes, drugs and herbicides synthesis and other industrial processes. Such compounds exhibit high toxicity for aquatic environment and for aquatic life. So, due to their high toxicity is important to treat waters with phenols content. For the treatment of waste waters containing phenols or phenolic compounds several unconventional methods are applied, such as: inverse osmosis, coagulation, solvent extraction, flotation–coagulation combined processes, adsorption, and anaerobic processes. From all used remediation processes adsorption has a higher applicability degree due to its main advantages: simplicity, ease of use and operation and high efficiency. Through time activated carbon and ashes were used as adsorbent materials for phenols remediation, but such materials present the main disadvantage of low regeneration degree. Thus, it is important to develop and use new adsorbents with higher regeneration degree and longer life time. Polymeric materials have been used for removal of organic compounds and/or metal ions from contaminated water due to their versatility in functionality, morphology and texture properties. Chemical modification of polymeric matrices with pendant functional groups is a valuable method used to improve the surface and interface chemistry of polymeric adsorbents, to achieve better adsorption performance and to design tailor-made adsorbents with respect to specific pollutants. In present study new adsorbent materials were obtained starting from chloromethylated styrene-divinylbenzene copolymers with different degrees of crosslinking (6.7%, 12% and respectively 15% DVB), functionalized by reaction with 3-hydroxibenzaldehyde. The polymeric intermediates were further modified by polymer-analogous reaction with iso-propylamine and diethylphosphite with the aim to improve their adsorptive properties. The obtained polymeric adsorbents were tested for remediation of waters containing phenol (P), 2,3-dimethylphenol (2,3-DMP) and 2,4,6-trimethyl-phenol (2,4,6-TMP). Based on obtained experimental data the adsorption mechanism, process kinetics and thermodynamics were studied.

Synthesis of nanocrystalline LiCoO2powders by polymeric combustion process: an investigation on the effect of different carboxylic acids as fuel

AbstractLayer-structured nanocrystalline LiCoO2 powders were prepared by polymeric combustion process using metal nitrates and different carboxylic acids as precursors. Three different carboxylic acids named citric, tartaric, and polyacrylic were experimented in order to synthesize ultrafine LiCoO2 nanopowders. The combustion behavior of polymeric intermediates and the formation of LiCoO2 structures were identified through thermogravimetry and differential thermal analyzer (TG/DTA), FTIR, XRD, SEM, and TEM investigations. The correlation between the microstructure of the polymeric intermediates and their thermal degradation profile was observed by their scanning electron micrographs and TG/DTA thermograms. The result found that the effective combustion was occurred only in citric acid (CA)-derived polymeric intermediate due to its porous microstructure, which leads to the formation of phase pure LiCoO2 powders with no organic residual. The TEM analysis reveals that the particle size of the synthesized LiC...

Formation and Degradation of Intermediate Hemoglobin Polymers are Responsible for the Cooperativity of Oxygen Binding Isotherms

According to the MWC model, cooperativity is due to the equilibrium between the lower affinity T form and the higher affinity R form at the beginning and end of oxygen binding isotherm. The model disregards the energy barrier necessary for preventing the T and R forms relaxing into a single conformation system. Also, the difference between the binding Gibbs free energy of the two affinities at pH 9.0 is ΔG=2000 cal/mole. It means that at equilibrium the energy level of the T form increases by 2.0 Kcal/mole. This increase is inconsistent with the zero sum of heat exchanges needed for equilibriums. To solve these problems we tested the response of the isotherm to osmotic pressure, heat, and protein concentration. Osmotic stress reveals a higher volume/surface ratio of the T form, suggesting a more spherical shape. Increasing protein concentration decreases the oxygen affinity of the system indicating formation of transient polymeric forms, with low oxygen affinity. Enthalpies of the intermediates show a strong absorption of heat at the third oxygenation step. This is the heat necessary for polymerizing tetrameric Hb into quinary structures, as in the fibers of HbS, The net absorption and release of heat, of the enthalpies of the conformational changes, is a negative ΔG=-2000 cal/mole, reflecting the degradation of the quinary polymers into the quaternary T and R forms. This heat released to the system compensates to zero the energy absorbed by the T form upon deoxygenation. It should be stressed that the high energy level of polymeric intermediates is the energy barrier preventing the direct relaxation of the T and R conformations into one another. This molecular mechanics explains the cooperativity of oxygen binding isotherm.

Low temperature processing and magnetic properties of zinc ferrite nanoparticles

Zinc ferrite nanoparticles were successfully synthesized by Pechini process and the effect of the calcination temperature and precursors on microstructure was investigated in detail using XRD, FT-IR, SEM, and TEM techniques. The thermal behavior of polymeric intermediates was studied by STA (TG–DTG–DTA) thermograms. Magnetic properties were studied by VSM technique. Results indicated that nanocrystalline zinc ferrite particles with a single-phase spinel structure were obtained. The nanoparticles possessed a spherical morphology with a particle size of 18–62nm depending on the calcination temperature and precursor where higher calcination temperatures resulted in larger particles. It was also found that larger particles formed when polyethylene glycol-1000 (PEG) is used as precursor, while using ethylene glycol (EG) leaded to a smaller particle size. Magnetic properties of the samples were found to be greatly affected by the average crystallite size. The saturation magnetization values increased from 0.72 to 7.21emu/g when the calcination temperature was raised from 400 to 900°C. At a constant calcination temperature, the samples prepared with EG showed lower magnetization than those prepared with PEG. Results also showed that the utilization of PEG precursor decreased the porosity content of polymeric intermediates, which caused a poor combustion with long duration resulting in residual organic impurities in the samples. We show that magnetic characteristics of zinc ferrite nanoparticles can be precisely tuned by changing the calcination temperature and the precursors, expanding the range of practical applications of this material.

Preparation and Characterization of Barium Titanate (BaTiO3) Nano-Powders by Pechini Sol-Gel Method

In this work, barium titanate (BaTiO3) powders were synthesized via two Pechini sol-gel processes using citric acid and polyethylene glycol-6000 as chelating agents. Attempts had been made to understand the thermal behavior of the polymeric intermediates with the help of thermogravimetry-differential scanning calorimetry (TG-DTG-DSC) thermograms. The structural coordination of as-prepared polymeric intermediates was investigated by Fourier transform infrared (FTIR) analysis. The phase and structure of the powders calcined at different temperatures were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Preparation of the polymeric precursors can influence the mechanism of the BaTiO3 synthesis. The formed intermediate phase BaCO3 appears in gel-2 system, and BaCO3 phase does not disappear at 720°C. The formed intermediate phases of gel-1 differ from that of gel-2. The intermediate phases of gel-1 are anatase TiO2 and rutile TiO2, and the intermediate phase BaCO3 doesn't appear in gel-1system. When the powders are calcined at 720°C, the particles of gel-1 system are agglomerated spheres with about 25 nm, but the particles of gel-2 system have varied shapes.

Preparation and characterization of single-phase α-Fe 2O 3 nano-powders by Pechini sol–gel method

In this work, single-phase α-Fe 2O 3 nano-particles were first synthesized via Pechini sol–gel method using citric acid and polyethylene glycol-6000 as chelating agents. The structural coordination of as-prepared polymeric intermediates was investigated by FTIR analysis. Thermal behavior of the polymeric intermediates was studied by TG-DTG-DSC thermograms. The structure of the powders calcined at different temperatures was characterized by XRD and FESEM. The single-phase α-Fe 2O 3 nano-powders with uniform size were prepared when the polymeric intermediate calcined at 600 °C, and the lowest particle size was found to be 30 nm.

Effect of Pressure on Thermal Stability and Decomposition of KDP Crystal

Effect of pressure on thermal behavior of KDP crystals is investigated by using the in-situ infrared reflective spectra. Compared with that under normal atmosphere, the onset temperature of decomposition under pressure of 1 MPa is improved to from 210°C to 213°C, suggesting that the thermal stability of KDP is enhanced. Under pressure of 2 MPa, the thermal stability is deteriorated and KDP begins to decompose at 183°C. Under normal atmosphere KDP decomposes in route of translating to K4P2O7 firstly, and then to KPO3. Under pressures of 1 MPa and 2MPa, KDP translates to KPO3 directly without any other polymeric intermediates.

Acrylamide assisted polymeric citrate route for the synthesis of nanocrystalline ZrO 2 powder

Nanocrystalline ZrO 2 powders have been prepared using acrylamide assisted polymeric citrate combustion (autoignition) route. Process parameters (i.e., total metal ions to citric acid ratio) were varied for the formation of polymeric resin in order to obtain the final product with desired properties (organic free, smaller crystallite size, etc.). The effect of three different citric acid amounts in the formation of nanocrystalline ZrO 2 powder was investigated using FTIR, XRD, TG/DTA and SEM-EDS, respectively, to identify the structural coordination, phase, thermal behavior and microstructure of the polymeric intermediates as well as the final ZrO 2 powders. Organic free ZrO 2 powder with two different phases of metastable t-ZrO 2 and m-ZrO 2 were prepared by calcining the polymeric intermediates at 600 °C. The lowest crystallite was found to be 18 and 16 nm, respectively, for the t-ZrO 2 and m-ZrO 2 phases prepared with total metal ions to citric acid ratio of 1:3.

Autoreduction of Pd−Co and Pt−Co Cyanogels: Exploration of Cyanometalate Coordination Chemistry at Elevated Temperatures

Cyanogels are coordination polymers made from the reaction of a chlorometalate and a cyanometalate in aqueous solution, which undergo a sol-gel transition to form stable gels. At temperatures above 240 degrees C, the cyanide ligand acts as a reducing agent and reduces the metal centers to lower oxidation states. To understand the mechanism of the autoreduction, the thermal reduction of the Pd-Co cyanogel system formed by the reaction of PdCl4(2-) and Co(CN)6(3-) was studied in an inert atmosphere. It was found that the reduction proceeds through two polymeric cyanide-containing intermediates, CoPd(CN)4 and Pd(CN)2, that form upon reduction of Co(3+) to Co(2+) and involves a significant rearrangement of the coordination structure. The two intermediates upon further heating reduce to metallic products, which by solid-state diffusion form a single Pd/Co alloy product. CoPd(CN)4 was found to have a hydrated form Co(H2O)2Pd(CN)4 x 4 H2O with a layered structure crystallizing in an orthorhombic Pnma space group. The Pt-Co cyanogel was found to autoreduce via a similar route. CoPt(CN)4 was confirmed as an intermediate. Understanding of the mechanism of the cyanogel autoreduction is an important step toward better understanding of opportunities that cyanogels offer in materials chemistry, as well as an expansion of the knowledge of coordination chemistry at elevated temperatures in general.

Ammonium carboxylates assisted combustion process for the synthesis of nanocrystalline LiCoO 2 powders

Nanocrystalline LiCoO 2 powders were synthesized by combustion process using three different ammonium carboxylates named ammonium acetate (AA), ammonium citrate (AC) and ammonium tartarate (AT) as fuels and metal nitrates as the source of metal ions as well as oxidants. Effect of three different ammonium carboxylates on the synthesis of nanocrystalline LiCoO 2 powders was investigated through FTIR, XRD, TG/DTA and SEM techniques. FTIR and XRD analysis confirmed that the LiCoO 2 phase could obtain by calcining the polymeric intermediates at 450 °C for 12 h. Among the three different fuels, ammonium citrate assisted combustion process exhibited the formation of organic free phase pure nanocrystalline LiCoO 2 powders. The average crystallite size of the LiCoO 2 powder prepared at 450 °C for 12 h by ammonium citrate assisted process is found to be 24 nm.

Novel urea assisted polymeric citrate route for the synthesis of nanocrystalline spinel LiMn 2O 4 powders

Urea assisted polymeric citrate route was investigated for the synthesis of nanocrystalline spinel LiMn 2O 4 powders using metal nitrates/acetates, citric acid and urea under acidic condition at 300 °C. Optimum total metal ions to urea ratio was identified for the synthesis of organic free, phase pure nanocrystalline LiMn 2O 4 powders. Addition of urea changes the microstructure and combustion mechanism of polymeric intermediates as well as the structural coordination and phase formation of the LiMn 2O 4 powders, which are, respectively, confirmed through SEM, TG/DTA, FTIR and XRD analysis. Organic free phase pure nanocrystalline LiMn 2O 4 powder was synthesized by urea assisted polymeric citrate route with the total metal ions to urea ratio of 1:2 at 300 °C and the average crystallite size was found to be 19 nm.

Synthesis and electrochemical studies on Al 2O 3 coated LiNi 0.5Co 0.44Fe 0.06VO 4 for lithium ion batteries

LiNi 0.5Co 0.44Fe 0.06VO 4 cathode material has been synthesized by a citric acid:polyethylene glycol polymeric method at 723 K for 5 h in air. The surface of the LiNi 0.5Co 0.44Fe 0.06VO 4 was coated with various wt.% of Al 2O 3 by a wet chemical procedure and heat treated 873 K for 2 h in air. The samples were characterized by XRD, FTIR, SEM, and TEM techniques. XRD patterns expose that the complete crystalline phase occurred at 723 K and there was no indication of new peaks for the coated samples. FTIR spectra show that the complete removal of organic residues and the formation of LiNi 0.5Co 0.44Fe 0.06VO 4. TG/DTGA results reveal that the formation of LiNi 0.5Co 0.44Fe 0.06VO 4 occurred between 480 and 670 K and the complete crystalline occurred at 723 K. SEM micrographs show the various morphological stages of the polymeric intermediates. TEM micrographs of the pristine LiNi 0.5Co 0.44Fe 0.06VO 4 reveal that the particle size ranged from 130 to 150 nm and Al 2O 3 coating on the fine particles was compact and had an average thickness of about 15 nm. The charge–discharge experiments were carried out between 2.8 and 4.9 V (versus Li) at a current rate of 0.15 C. The 1.0 wt.% Al 2O 3 coated sample had the best electrochemical performance, with an initial capacity of 65 mAh g −1 and capacity retention of 60% after 50 cycles. The electrochemical impedance behavior suggests that the failure of pristine cathode performance is associated with an increase in the impedance growth on the surface of the cathode material upon continuous cycling.

Synthesis and characterization of a new inverse spinel LiNi1/3Co1/3Mn1/3VO4 for lithium-ion batteries

An electrochemically active LiNi1/3Co1/3Mn1/3VO4 cathode material was synthesized by a citric acid:polyethylene glycol (CA:PEG) polymeric method, followed by calcination at 723 K for 5 h in air. X-ray diffraction (XRD) patterns showed the complete formation of a crystalline phase occurred when heated at 723 K. Scanning electron microscope (SEM) micrographs showed the various stages of morphology for the polymeric intermediates of the LiNi1/3Co1/3Mn1/3VO4 compound. Transmission electron microscope (TEM) imaging exposed that particle size ranged from ∼170 to 190 nm. The cells using LiNi1/3Co1/3Mn1/3VO4 as a cathode could be cycled between 2.8 and 4.9 V (vs. Li) at a current rate of 0.15C. The galvanostatic cycling study suggests that cycle stability and capacity retention were enhanced for LiNi1/3Co1/3Mn1/3VO4 prepared with a CA:PEG ratio of 3:1. The dQ/dV vs. voltage plots revealed the redox potentials and slower impedance growth for the synthesized LiNi1/3Co1/3Mn1/3VO4 cathode material.

Effect of different ethylene glycol precursors on the Pechini process for the synthesis of nano-crystalline LiNi 0.5Co 0.5VO 4 powders

Effect of different ethylene glycol (ethylene glycol, polyethylene glycol-400 and polyethylene glycol-4000) precursors on the Pechini process for the synthesis of nano-crystalline LiNi 0.5Co 0.5VO 4 powders was investigated. The structural coordination of as-prepared and calcined polymeric intermediates was investigated by FTIR analysis. Thermal behavior of the polymeric intermediates was studied by DSC thermograms. Effect of different ethylene glycols on the microstructure of polymeric intermediates was identified by SEM analysis. The inverse spinel phase of the obtained LiNi 0.5Co 0.5VO 4 powders was confirmed by comparing the X-ray diffraction spectra with JCPDS data and the crystallite size was calculated using XRD data and Scherrer's formula. The lowest crystallite size was found to be 49 nm for the calcined polymeric intermediate, at 450 °C for 12 h, prepared with ethylene glycol (EG).

Effect of ethylene glycol on polyacrylic acid based combustion process for the synthesis of nano-crystalline nickel ferrite (NiFe 2O 4)

Nano-crystalline nickel ferrite (NiFe 2O 4) was synthesized using combustion process with metal nitrates as Ni and Fe ion sources and polyacrylic acid (PAA) as a chelating agent. The effect of ethylene glycol (EG) addition to polyacrylic acid on the synthesis of nano-crystalline NiFe 2O 4 powders was investigated through DSC, FTIR, SEM and XRD measurements. Thermal behavior, structural coordination, microstructure and crystalline phase formation of as prepared and also calcined polymeric intermediates were, respectively, obtained from the analysis of DSC, FTIR, SEM and XRD results. The crystallite size was calculated using XRD data and Scherrer's formula. The smallest crystallite size is found to be 14 nm for the phase pure NiFe 2O 4 powder obtained from the polymeric intermediates, calcined at 450 °C for 12 h, synthesized by PAA based gel combustion route with the total metal ions to EG ratio (M/EG) of 1:0.5.

Glycerol-assisted gel combustion synthesis of nano-crystalline LiNiVO 4 powders for secondary lithium batteries

Glycerol assisted gel combustion route (GGCR) was used for the synthesis of nano-crystalline inverse spinel LiNiVO 4 powders, with metal nitrates, citric acid and glycerol for three different total metal ions to glycerol ratios (M/G) as 1:1, 1:2 and 1:3. In this study, the effect of total metal ion to glycerol ratio on the formation of the nano-crystalline LiNiVO 4 phase was investigated and discussed. The thermal behavior and structural coordination of the as prepared as well as the calcined polymeric intermediates at different temperatures were investigated, respectively, using the DSC and FTIR measurements. The microstructure of the polymeric intermediates was identified by taking the scanning electron microscopy (SEM) pictures. The formation of the inverse spinel LiNiVO 4 phase, obtained from the calcined intermediates, was confirmed by comparing the observed X-ray diffraction spectra with the respective JCPDS standard. The crystallite size was calculated using the Scherrer's formula and the smallest crystallite size of 39 nm was observed for the LiNiVO 4 powders obtained from the polymeric intermediate, calcined at 450 °C for 12 h, synthesized using the GGCR with M/G=1:1.

HPMA Copolymers Platinates Containing Dicarboxylato Ligands. Preparation, Characterisation and In Vitro and In Vivo Evaluation

N -(2-Hydroxypropyl)methacrylamide (HPMA) copolymer platinates were prepared from polymeric intermediates containing Gly-Phe-Leu-Gly side chains terminating in either malonate or aspartate dicarboxylato ligands. Platinum(II) was bound by reaction of the dicarboxylato ligands with cis -[Pt(NH 3) 2 (H 2 O) 2] 2+. The HPMA copolymer platinates obtained had a Mw of 29,000-31,000 Da and a platinum loading of approximately 10 wt% (by AAS). This is close to the theoretical maximum value. The release rate of platinum species in vitro at pH 7.4 correlated with the expected stability of the 6 and 7 membered chelate rings; 14%/24 h platinum released in the case of the malonate and 68%/24 h platinum released in the case of the aspartate. Cisplatin and the aspartate conjugate displayed similar toxicity in vitro against B16F10 and COR-L23 cells while the malonate was at least 8-fold less toxic. The malonate conjugate showed significantly improved activity (T / C =1.27-1.5) when compared with cisplatin (T / C =1.18) that was not active when administered intravenously to treat a subcutaneous B16F10 tumour. The conjugate was at least 20-fold less toxic than cisplatin in vivo. After i.v. administration, the platinum accumulation in B16F10 tumour tissue showed a 19-fold increase in Pt AUC for the malonate conjugate when compared to cisplatin administered equi-dose at its maximum tolerated dose (MTD) (1 mg/kg).