Single Solvent Systems Research Articles

Investigation of piroctone olamine delivery to the skin from single, binary and ternary solvent systems.

Disruption of the protective stratum corneum barrier increases the skin's vulnerability to microorganisms and facilitates conditions such as dandruff. Dandruff is a disorder of the scalp that causes increased scaling of the SC and is associated with Malassezia fungus. Consequently, many anti-dandruff commercial products use anti-fungal active ingredients such as piroctone olamine also known as Octopirox (OPX). OPX is an active ingredient used in a number of topical preparations for the management of dandruff. The characterization of the physicochemical properties of OPX was previously reported. The aim of the present work was to investigate a range of solvent systems for their effects on OPX interaction with human skin. The solvents used in this study were propylene glycol (PG), diethylene glycol monoethyl ether or Transcutol® (TC), PG monolaurate (PGML), isopropyl myristate (IPM), caprylic/capric triglyceride or Labrafac™ Lipophile WL 1349 (LAB), PG caprylate or Capryol® 90 (CAP), isostearyl isostearate (ISIS) and Plurol® Oleique CC 497 (PIOI). The single solvent systems evaluated were PG, TC, PGML, IPM, ISIS and CAP. For the binary solvent systems, PG and TC were examined. Ternary solvent systems consisted of: PG, TC and LAB; PG, PGML and LAB; and PG, TC and IPM. The concentration of OPX used was 1% (w/v). Heat-separated human epidermis was used for 24 h permeation experiments performed under finite dose conditions; mass balance studies were also conducted. For the six single solvents examined no permeation was evident. Skin permeation of OPX was observed for binary and ternary solvent systems. The highest permeation for all PG:TC binary solvent system ratios tested was from the PG:TC (75:25) system. For the ternary solvent systems investigated, highest cumulative permeation of OPX was observed for PG:PGML:LAB (60:30:10). Considering all systems, PG:TC (75:25) delivered the greatest amount of OPX through the skin. Although OPX is deposited in the skin following the application of neat solvents, higher skin retention values were generally observed for binary and ternary systems. To our knowledge, this is the first study to examine the permeation behaviour of OPX for a range of single, binary and ternary solvent systems.

Pyrolysis of hydrochars obtained from blackcurrant pomace in single and binary solvent systems

The two-stage conversion of blackcurrant pomace as an industrial wet-type waste is presented. Firstly, the pomace was hydrothermally processed in a single solvent (water) and a binary solvent system (water mixed with isopropanol) at low and moderate processing temperatures (225 and 275 °C, respectively). More specifically, the focus was put on investigating the effect of operating conditions on the change in the yield distribution of bioproducts, particularly solid hydrochar. Also, the composition, textural properties, and morphology of hydrochars were examined by DRIFT and XRD, low-temperature nitrogen adsorption, and SEM, respectively. In the subsequent step, the upgrading of resultant hydrochars via fast pyrolysis by using microscale techniques (pyrolysis coupled with gas chromatography and mass spectrometry) and thermogravimetric analysis was done. The studies proved that the proposed approach allows to obtain alternative products exhibiting high energy density (21.9–29.3 MJ kg−1) that could be useful for power and heat generation. It was found that conversion in the binary solvent system involves a noticeably deeper decomposition of the pristine biomass structure. Furthermore, through two-stage processing, it is possible to obtain value-added chemicals, such as hydrocarbons, with the potential to serve as advanced biocomponents or reagents for the chemical industry.

Biphenyl-Induced Superhelix in l -Phenylalanine-Based Supramolecular Self-Assembly with Dynamic Morphology Transitions

Biphenyl-Induced Superhelix in <scp>l</scp> -Phenylalanine-Based Supramolecular Self-Assembly with Dynamic Morphology Transitions

Binary Solvent Systems for Piezoelectric Printing Crack-Free PAM/ZrOx Hybrid Thin Films through Nanostructure Modulation.

Polymer/oxide hybrid thin films, which have excellent electrical and mechanical performance, can be effectively fabricated through the sol-gel process, showing great potential in the future printed electronics. However, gelation of polymer/oxide ink systems can easily occur during a thermal process in which case capillary stress can lead to the crack of printed films due to the long period of stress accumulation. To solve this problem, the effect of different solvent systems on formed PAM/ZrOx hybrid films, which were printed by piezoelectric printing, was studied in this paper, including single solvent systems of glycol and binary solvent systems of glycol and water. The result showed that the microstructure characteristics and mechanical properties of hybrid nanostructures formed in different solvent systems varied significantly, and crack behavior can be regulated by simply adjusting the water volume ratio of the solvent system. The crack formation was significantly inhibited when the water volume ratio reached 25%.

Highly Efficient Synthesis of Glucose Fatty Acid Esters Catalyzed by High Performance Lipase Preparations

Glucose fatty acid esters were synthesized using cross-linked enzyme aggregates (CLEAs), protein coated microcrystals (PCMCs) and cross-linked protein coated microcrystals (CLPCMCs) of Candida antarctica lipase B (CALB) as biocatalyst designs in single and mixed solvent systems. Up to 90% conversion and more than 99% regioselectivity were obtained using vinyl acetate as the acyl donor in a solvent system composed of 2-methyl-2-butanol (2M2B) and 30% (v/v) DMSO, with CALB CLEAs within 45 min. Similar results were obtained with CALB CLPCMCs as the biocatalyst under the same reaction conditions. This approach was then extended to the synthesis of glucose esters with higher acyl chain length. The synthetic strategy used in this work can potentially be extended for the fast and regioselective esterification/transesterification of other sugars as well.

Development of metallosupramolecular phosphatases based on the combinatorial self-assembly of metal complexes and organic building blocks for the catalytic hydrolysis of phosphate monoesters

The phosphorylation and dephosphorylation of proteins and other intracellular molecules are important reactions in living systems and are generally controlled by the action of kinases and phosphatases. The design and synthesis of artificial mimics of natural enzymes are important research subjects in bioorganic and bioinorganic chemistry. A supramolecular strategy based on the three-dimensional self-assembly of molecular building blocks would be useful for the construction of artificial supramolecular complexes. The main focus of this review is on artificial mimics of natural phosphatases that contain dimetallic cores in their active sites. Previous examples of artificial mimics of alkaline phosphatases (AP) constructed covalently are initially presented, then followed by a description of artificial metallosupramolecular complexes formed by the combinatorial self-assembly of different bis(Zn2+-cyclen) complexes containing 2,2′-bipyridyl (bpy) linker (cyclen = 1,4,7,10-tetraazacyclododecane), cyanuric acid or barbital (Bar) units, and Cu2+ ion in single or two-phase solvent systems. It is now thought that the appropriate combination of the various building blocks and solvent systems (single- and two-phase solvent systems) can strongly assist in developing the artificial systems that accelerate and catalyze the hydrolysis of a phosphate monoester, mono(p-nitrophenyl) phosphate (MNP). Such approaches would be useful in terms of understanding the mechanism of action of naturally occurring enzymes and to develop biologically active, bioorthogonal, and versatile supramolecular catalysts.

Study of Polymorphism on Pargeverine Hydrochloride

Objectives: Screening active pharmaceutical ingredients for polymorphs is of utmost importance in drug development to enable stable APIs, robust manufacturing processes and reduction of costs incurred in switching over crystal forms. The current study deals with exploring polymorphism in Pargeverine Hydrochloride using different solvents and solvent systems. Methods: Drug was crystallized by slow solvent evaporation of filtered saturated solution using either single or mixed solvent systems. The resultant crystals were evaluated for physical appearance and by Fourier transform Infrared Spectroscopy, Differential Scanning Calorimetry and Powder X-Ray Diffraction. Results: The physical appearance, melting points, pattern of heat flow for phase transition, peak temperature and the IR spectra and Powder X-Ray Diffraction pattern of the crystals of Pargeverine Hydrochloride in single and mixed solvent systems (50 solvent systems) did not show any marked difference from that of pure drug. Conclusion: From the results, it can be concluded that there were minimal possibilities of polymorph formation for Pargeverine HCl in the solvent/s or combination of solvents attempted, thus need for any specific controls to inhibit transition during its routine manufacturing process may not be required.

Exploiting the unique specialty of hydrazone functionality: Synthesis of a highly sensitive UV–Vis active solvatochromic probe

The unique physico-chemical attributes of the hydrazone functionality have been extensively studied for a diverse range of chemical, biological and analytical applications. The synthesis of a highly sensitive hydrazone based UV–Vis active solvatochromic probe that exhibits excellent sensitivity toward sensing of solvent polarity, microstructural changes and onset of micellization in aqueous systems was carried out. Specifically, synthesis of 2,4-dinitrophenyl-2-(2-nitrobenzylidene)hydrazone (DNPNBH), through an easy to carry, atom economical, one-pot single step approach via use of low-cost precursors viz. ortho-nitrobenzaldehyde and 2,4-dinitrophenyl hydrazine is presented. The UV–Vis absorption features of the synthesized hydrazone exhibit excellent sensitivity toward the polarity of its immediate microenvironment. The microenvironment polarity sensing potential of DNPNBH is demonstrated for some single solvent systems and DMF-Water mixture as a model binary solvent system and the results are supported by quantum mechanical calculations. Use of the DNPNBH as a probe (at concentrations many orders lower than required for conventional probes) to precisely reflect the onset of micellization and estimation of critical micelle concentration (CMC) of amphiphilic molecules (5.25 mM for SDS, 1.53 mM for CTAB and 0.055 mM for Brij56) in aqueous solutions is also demonstrated. The results clearly qualify the synthesized hydrazone as a highly sensitive UV–Vis probe that can be employed for reliable sensing of solvent polarity, composition dependence of physicochemical attributes in mixed solvent systems and the estimation of CMC of surfactant systems via spectrophotometry.

Topical delivery of niacinamide: Influence of neat solvents

Niacinamide (NIA) has been widely used in cosmetic and personal care formulations for several skin conditions. Permeation of topical NIA has been confirmed in a number of studies under infinite dose conditions. However, there is limited information in the literature regarding permeation of NIA following application of topical formulations in amounts that reflect the real-life use of such products by consumers. The aim of the present work was therefore to investigate skin delivery of NIA from single solvent systems in porcine skin under finite dose conditions. A secondary aim was to probe the processes underlying the previously reported low recovery of NIA following in vitro permeation and mass balance studies. The solubility and stability of NIA in various single solvent systems was examined. The solvents investigated included Transcutol® P (TC), propylene glycol (PG), 1-2 hexanediol (HEX), 1-2 pentanediol (1-2P), 1-5 pentanediol (1-5P), 1-3 butanediol (1-3B), glycerol (GLY) and dimethyl isosorbide (DMI). Skin permeation and deposition of the molecule was investigated in full thickness porcine skin in vitro finite dose Franz-type diffusion experiments followed by mass balance studies. Stability of NIA for 72h in the solvents was confirmed. The solubility of NIA in the solvents ranged from 82.9±0.8 to 311.9±4.5mg/mL. TC delivered the highest percentage permeation of NIA at 24h, 32.6±12.1% of the applied dose. Low total recovery of NIA after mass balance studies was observed for some vehicles, with values ranging from 55.2±12.8% to 106.3±2.3%. This reflected the formation of a number of NIA degradation by-products in the receptor phase during the permeation studies. Identification of other vehicles for synergistic enhancement of NIA skin delivery will be the subject of future work.

3-O-ethyl-l-ascorbic acid: Characterisation and investigation of single solvent systems for delivery to the skin

l-ascorbic acid (AA), commonly known as vitamin C, has been widely used in topical formulations for many years as an antioxidant and anti-aging ingredient. However, the physicochemical properties of AA are not optimal for skin uptake and the molecule is also unstable, readily undergoing oxidation on exposure to air. The compound 3-o-ethyl-l-ascorbic acid (EA) has been developed as a stable vitamin C derivative and has been used in topical products. The aims of this work were to conduct a comprehensive characterisation of physicochemical properties of EA as well as to investigate the influence of various neat solvents on EA skin delivery. Nuclear magnetic resonance (NMR), mass spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterise the molecule. The pKa of the compound and the partition coefficient logP(o/w) were experimentally determined. A new HPLC method for analysis of the molecule was also developed and validated. A number of solvents for topical preparations were selected based on their wide use as excipients in topical formulations, their potential to act as skin penetration enhancers and their favourable safety profiles. The solubility and stability of EA was examined. Skin permeation of the molecule in full thickness porcine skin in vitro was investigated using Franz-type diffusion cells. The melting point, log P(o/w) value and pKa value of EA were determined to be 114.39 ± 0.5 °C, −1.07 ± 0.03 and 7.72 ± 0.01 respectively. Skin penetration of EA was evident for the following vehicles 1,2 hexanediol (HEX), glycerol (GLY), propylene glycol (PG), 1,2 pentanediol (1-2P), isopropyl alcohol (IPA), propylene glycol monolaurate (PGML) and propylene glycol monocaprylate (PGMC). Skin uptake but no permeation through the skin was observed for Transcutol® (TC) and dipropylene glycol (DiPG), while no penetration was observed for the solvents 1,5 pentanediol (1-5P) and tripropylene glycol (TriPG). The findings of the permeation experiments confirm the potential of simple formulations to deliver EA to the skin. Studies are ongoing to identify complex vehicles for synergistic enhancement of EA skin penetration. To our knowledge this is the first study to conduct a comprehensive characterization of EA and examine its skin uptake and permeation properties in porcine skin.

Evaluation of radiochemical purities of routinely used radiopharmaceuticals: Three years’ experience of a single institute

Introduction: Radiochemical purity (RCP) is a routine quality control test carried out at nuclear medicine to determine the concentration of various chemical species present in the radiopharmaceuticals (RPs). The present work describes three years of experience in a single institute for the measurement of these impurities in the RPs preparations. Methods: The RCP of different cold kit preparations were performed by chromatographic methods. Specifically, a small drop of the aliquot was spotted on the specific paper acting as the stationary phase and then developed in different solvents as mobile phases. The developed chromatograms were then quantified for various chemical species by Mini TLC scanner or well type counter. Results: The retention factor (Rf) values for the different chemical species in the labeling of RP were measured by using single, double or triple solvent systems. It was observed that 2.70% of the kits had RCP less than the acceptable limit whereas 97.30% kits were found within the permissible levels. Conclusion: Chromatographic techniques used for the assessment of RCP offer sufficiently good results for identification and separation of different chemical impurities.

Water-Chloroform Interface Assisted Microstructure Tuning of Polypyrrole-Silver Sheets.

The liquid-liquid interface of two immiscible solvents remarkably controls the morphology of polymeric nanostructures as compared to the polymerization in single solvent systems. The polymerization of pyrrole in the water-chloroform medium using silver nitrate (AgNO3) as oxidant yields polypyrrole/silver (PPy/Ag) sheets. The water-chloroform interface acts as a template for the growth of PPy/Ag hybrids into sheets by preventing the secondary growth of silver associated pyrrole oligomers in a three-dimensional (3-D) manner. On the contrary, the 3-D growth of pyrrole oligomers into spherical shapes at the water-chloroform interface is observed when ammonium persulfate (APS) is used as the oxidant. Transmission electron microscopic and scanning electron microscopic images reveal the sheetlike morphology of PPy/Ag with a relatively uniform distribution of Ag NPs (∼100 nm) on PPy sheets. The ratio of aqueous-organic bisolvent and the concentration/type of oxidant have a distinct effect on morphology, crystallinity, and electrical properties of PPy/Ag sheets. The dispersed PPy/Ag sheets are stable in moderately polar solvents up to 2 weeks. The electrochemical behavior of PPy/Ag sheets is confirmed by H2O2 sensing capability through cyclic voltammetry experiments. The antibacterial activity toward E. coli and S. aureus is quantitatively assessed using the minimum bactericidal concentration (MBC) determination.

Solubility and thermodynamic properties of 5-nitrofurazone form γ in mono-solvents and binary solvent mixtures

In this work, the solubility of the γ - polymorphic form of 5-nitrofurazone (5-nitro-2-furaldehyde semi-carbazone) in mono-solvent systems and binary solvent mixtures was measured from 278.15 to 313.15 K, using a UV spectroscopic method. The results revealed that the solubility increased with increasing temperature in all investigated solvents within this temperature range. The experimental solubility data in the single solvent systems was well represented with the modified Apelblat equation and the NRTL model, while the λh equation and the NRTL model were used to correlate the experimental solubility data in the case of the binary solvent mixtures. In all cases, these models were shown to have an average relative deviation of lower than 5%. In addition, the thermodynamic mixing and dissolution properties of the γ - form of 5-nitrofurazone, in all investigated mono-solvent systems and binary solvent mixtures, were calculated based on NRTL model and experimental solubility data.

In Situ GIWAXS Analysis of Solvent and Additive Effects on PTB7 Thin Film Microstructure Evolution during Spin Coating.

The influence of solvent and processing additives on the pathways and rates of crystalline morphology formation for spin-coated semiconducting PTB7 (poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)-carbonyl]-thieno[3,4-b]thiophenediyl]]) thin films is investigated by in situ grazing incidence wide-angle X-ray scattering (GIWAXS) and optical reflectance, to better understand polymer solar cell (PSC) optimization approaches. In situ characterization of PTB7 film formation from chloroform (CF), chlorobenzene (CB), and 1,2-dichlorobenzene (DCB) solutions, as well as CB solutions with 1% and 3% v/v of the processing additives 1-chloronapthalene (CN), diphenylether (DPE), and 1,8-diiodooctane (DIO), reveals multiple crystallization pathways with: (i) single-solvent systems exhibiting rapid (<3 s) crystallization after a solvent boiling point-dependent film thinning transition, (ii) solvent + additive systems exhibiting different crystallization pathways and crystallite formation times from minutes (CN, DPE) to 1.5 h (DIO). Identifying crystalline intermediates has implications for bulk-heterojunction PSC morphology optimization via optimized spin-casting processes.

Solubility and Dissolution Thermodynamic Data of Cefpiramide in Pure Solvents and Binary Solvents

The solubility of cefpiramide in five pure solvents (water, ethanol, 1-propanol, 2-propanol, and 1-butanol) and two binary solvent systems (water + ethanol or water + 2-propanol) was measured by a steady-state method, from 278.2 to 303.2 K, under atmospheric pressure. The initial mole fraction of alcohol (ethanol or 2-propanol) in the binary systems ranged from 0 to 1. It is found that the solubility increases with increasing temperature in the experimental range and shows a quasi-S-shaped curve with the increase of the initial mole fraction of alcohol. The modified Apelblat equation was used to simulate the solubility data, and gives a maximum mean relative deviation (MRD) of 0.47% for the single solvent systems, and a maximum MRD of 1.03 and 1.15% for the ethanol + water and 2-propanol + water systems, respectively. The combined model of the Jouyban–Acree and modified Apelblat equations, both temperature-dependent and solvent-composition-dependent, was simplified to correlate the solubility data of binary solvent mixtures in the initial mole fraction range of alcohol from 0 to 0.9, and gives a MRD of 9.83 and 6.49% for the ethanol +water and 2-propanol + water systems, respectively. The dissolution thermodynamic properties in the pure solvents and two binary mixtures were calculated based on the van’t Hoff equation. The calculation results indicate that the dissolution process of cefpiramide is endothermic in the pure solvents, and entropically driven in the four alcohols but not in water. The dissolution process is endothermic in the two binary mixtures.

Prediction of the solubility in lipidic solvent mixture: Investigation of the modeling approach and thermodynamic analysis of solubility

Self-micro emulsifying drug delivery system (SMEDDS) is one of the methods to improve solubility and bioavailability of poorly soluble drug(s). The knowledge of the solubility of pharmaceuticals in pure lipidic solvents and solvent mixtures is crucial for designing the SMEDDS of poorly soluble drug substances. Since, experiments are very time consuming, a model, which allows for solubility predictions in solvent mixtures based on less experimental data is desirable for efficiency. Solvents employed were Labrafil® M1944CS and Labrasol® as lipidic solvents; Capryol-90®, Capryol-PGMC® and Tween®-80 as surfactants; Transcutol® and PEG-400 as co-solvents. Solubilities of both drugs were determined in single solvent systems at temperature (T) range of 283–333K. In present study, we investigated the applicability of the thermodynamic model to understand the solubility behavior of drugs in the lipiodic solvents. By using the Van’t Hoff and general solubility theory, the thermodynamic functions like Gibbs free energy, enthalpy and entropy of solution, mixing and solvation for drug in single and mixed solvents were understood. The thermodynamic parameters were understood in the framework of drug–solvent interaction based on their chemical similarity and dissimilarity. Clotrimazole and Fluconazole were used as active ingredients whose solubility was measured in single solvent as a function of temperature and the data obtained were used to derive mathematical models which can predict solubility in multi-component solvent mixtures. Model dependent parameters for each drug were calculated at each temperature. The experimental solubility data of solute in mixed solvent system were measured experimentally and further correlated with the calculates values obtained from exponent model and log-linear model of Yalkowsky. The good correlation was observed between experimental solubility and predicted solubility.

Electrospinning of Grooved Polystyrene Fibers: Effect of Solvent Systems.

Secondary surface texture is of great significance to morphological variety and further expands the application areas of electrospun nanofibers. This paper presents the possibility of directly electrospinning grooved polystyrene (PS) fibers using both single and binary solvent systems. Solvents were classified as low boiling point solvent (LBPS): dichloromethane (DCM), acetone (ACE), and tetrahydrofuran (THF); high boiling point solvent (HBPS): N,N-dimethylformamide (DMF) and cyclohexanone (CYCo); and non-solvent (NS): 1-butanol (BuOH). By the systematic selection and combination of these solvents at given parameters, we found that single solvent systems produced non-grooved fibers. LBPS/DMF solvent systems resulted in fibers with different grooved textures, while LBPS/CYCo led to fibers with double grooved texture. Grooved fibers can also be fabricated from LBPS/LBPS, NS/LBPS, and NS/HBPS systems under specific conditions. The results indicated that the difference of evaporation rate (DER) between the two solvents played a key role in the formation of grooved texture. The formation of this unique texture should be attributed to three separate mechanisms, namely void-based elongation, wrinkle-based elongation, and collapsed jet-based elongation. Our findings can serve as guidelines for the preparation of ultrafine fibers with grooved secondary texture.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-0949-5) contains supplementary material, which is available to authorized users.

Comparative Study on the Solid Electrolyte Interface Formation by the Reduction of Alkyl Carbonates in Lithium Ion Battery

One of the major concerns in lithium ion battery is the composition of the electrolytes as it governs some of the vital physicochemical properties of the electrolytes such as viscosity, ionic conductivity, thermal stability and wettability. Most important properties of lithium ion batteries are related to the properties of the solid electrolyte interface (SEI) layer formed on the electrode surface. The SEI in turn is mainly dependent on the electrolyte composition [1]. Therefore, understanding the nature, mechanism and property of the SEI formation in different electrolyte composition is crucial in selecting electrolytes. In this work, we report a direct comparison of the reduction of propylene carbonate (PC), ethylene carbonate (EC) and diethyl carbonate (DEC) as a single, binary and ternary solvent systems. Battery performance test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) is employed to study the nature of the surface films formed. The reduction products are determined by using ex-situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), in the glove box, after employing linear sweep voltammetry (LSV) to certain potential regions. EC/PC/DEC based electrolyte shows better capacity retention and less impedance than the EC/PC system. In all systems, the FTIR results indicate the formation of (CH3CH2OCO2Li)2 and Li2CO3 due to the reduction of PC. EC is reduced to (CH2OCO2Li)2 and Li2CO3 in both the binary and ternary solvent system. The FTIR result at the potential where DEC reduction occurs shows the formation of (CH2=CH-OCO2CH2CH3)Li which is less stable and forms a less-passivating layer in the first cycle. However, this product can further react with another species in the subsequent cycles and form a stable SEI. [1] A.J. Gmitter, J. Gural, G.G. Amatucci, J. Power Sources, 217 (2012) 21-28.[2] K. Xu, J. Electrochem. Soc., 156 (2009) A751-A755.[3] G.V. Zhuang, H. Yang, B. Blizanac, P.N. Ross, Electrochem. Solid-State Lett, 8 (2005) A441-A445.

Comparative Study on the Solid Electrolyte Interface Formation by the Reduction of Alkyl Carbonates in Lithium ion Battery

Mixed alkyl carbonates are widely used as solvent for a various lithium-ion battery applications. Understanding the behavior of each solvent in the mixed system is crucial for controlling the electrolyte composition. In this paper, we report a systematic electrochemical and spectroscopic comparison of the reduction of propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) when used as single (PC), binary (EC/PC, EC/DEC), and ternary (EC/PC/DEC) solvent systems. The reduction products are identified based on Fourier transform infrared spectroscopy (FTIR) after employing linear sweep voltammetry to certain potential regions and their possible formation mechanisms are discussed. FTIR analyses revealed that the reduction of EC and PC was not considerably influenced by the presence of other alkyl carbonates. However, DEC exhibited a different reduction product when used in EC/DEC and EC/PC/DEC solvent systems. The reduction of EC occurred before that of PC and DEC and produced a passivating surface film that prevented carbon exfoliation caused by PC. Battery performance test, cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscope is employed to study the surface films formed. The binary EC/DEC solvent system demonstrated more favorable performance, smaller impedance, and higher Li+ ion diffusivity than did the other solvent systems used in this study.

Solvent Effects on the Growth Morphology and Phase Purity of CL-20

The performance and stability of the high energy secondary explosive 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW, also known as CL-20) can be affected by factors including the phase purity of the bulk material, as well as the particle size, morphology, and defect density of the individual crystallites. Slow evaporation crystallization of CL-20 from 16 different single solvent and co-solvent systems was performed. The phase purity of the bulk material obtained was analyzed by powder X-ray diffraction, optical microscopy, and differential scanning calorimetry. These complementary methods confirmed that under most of the slow evaporation conditions examined, a concomitant mixture of two or more crystalline phases was usually obtained. Numerous individual crystal morphologies were determined using single crystal X-ray goniometry and compared against calculated BFDH morphologies. Examination of the packing interactions in the different CL-20 phases via Hirshfeld surface analysis provides some insight into why concomitant polymorphism is so frequently observed.