Insolubility In Organic Solvents Research Articles

Efficient production and characterization of melanin from Thermothelomyces hinnuleus SP1, isolated from the coal mines of Chhattisgarh, India.

In the present study, fungi were isolated and screened from barren land in south-eastern Coalfields limited (SECL) in Chhattisgarh, India. Out of 14 isolated fungi, only three fungal isolates exhibited pigmentation in screening studies. The isolated fungal strain SP1 exhibited the highest pigmentation, which was further utilized for in vivo production, purification, and characterization of melanin pigment. The physical and chemical properties of the fungal pigment showed insolubility in organic solvents and water, solubility in alkali, precipitation in acid, and decolorization with oxidizing agents. The physiochemical characterization and analytical studies of the extracted pigment using ultraviolet-visible spectroscopy and Fourier transform infrared (FTIR) confirmed it as a melanin pigment. The melanin-producing fungus SP1 was identified as Thermothelomyces hinnuleus based on 18S-rRNA sequence analysis. Furthermore, to enhance melanin production, a response surface methodology (RSM) was employed, specifically utilizing the central composite design (CCD). This approach focused on selecting efficient growth as well as progressive yield parameters such as optimal temperature (34.4°C), pH (5.0), and trace element concentration (56.24 mg). By implementing the suggested optimal conditions, the production rate of melanin increased by 62%, resulting in a yield of 28.3 mg/100 mL, which is comparatively higher than the actual yield (17.48 ± 2.19 mg/100 mL). Thus, T. hinnuleus SP1 holds great promise as a newly isolated fungal strain that could be used for the industrial production of melanin.

Synthesis and modification of poly (p‐phenylene terephthalamide) for production of light‐weight hybrid composite armors reinforced with polymer composite nanofiber mats

AbstractPoly (p‐phenylene terephthalamide) (PPTA) polymer was synthesized and then modified to eliminate the processing difficulties arising from its insolubility in organic solvents. The chemical structures of the synthesized PPTA and N‐butyl PPTA (BPPTA) were confirmed by elemental analysis, x‐ray diffraction, Fourier transform infrared (FTIR), and 13C‐NMR spectroscopy studies. As a result of modification, an aramid derivative that is soluble in some common solvents was obtained and added into polyacrylonitrile (PAN) matrix in solution. PAN/BPPTA composite nanofiber mats (CNMs) were fabricated by electrospinning. Mechanical tests showed that tensile strength increased by 119% with 3% BPPTA content. The fabricated CNMs were combined with aramid fabrics to produce laminated hybrid armors and ballistic tests were performed following the NATO Stanag 2920 standard. This is the first report about the integration of CNMs into multilayer armor configurations and resulted in improved ballistic limit velocity (V50) with a relatively very small weight gain and emergence of new energy absorption mechanisms.Highlights Alkylation of the para‐aramid yielded an organo‐soluble aramid derivative. Tensile strength of PAN nanofiber mat increased by 119% with 3% N‐butyl PPTA. Integration of the CNMs resulted in new ballistic impact absorption mechanisms. CNMs contribute to V50 with a very low mass gain due to their high surface area/mass.

Parahydrogen‐Induced Polarization of a Labeled, Cancer‐Targeting DNA Aptamer

AbstractEnhancing NMR signals of biomacromolecules by hyperpolarization offers exciting opportunities for diagnostic applications. However, their hyperpolarization via parahydrogen remains challenging as specific catalytic interactions are required, which are difficult to tune due to the large size of the biomolecule and its insolubility in organic solvents. Herein, we show the unprecedented hyperpolarization of the cancer‐targeting DNA aptamer AS1411. By screening different molecular motifs for an unsaturated label in nucleosides and in DNA oligomers, we were able to identify structural prerequisites for the hyperpolarization of AS1411. Finally, adjusting the polarity of AS1411 by complexing the DNA backbone with amino polyethylene glycol chains allowed the hydrogenation of the label with parahydrogen while the DNA structure remains stable to maintain its biological function. Our results are expected to advance hyperpolarized molecular imaging technology for disease detection in the future.

Parahydrogen-Induced Polarization of a Labeled, Cancer-Targeting DNA Aptamer.

Enhancing NMR signals of biomacromolecules by hyperpolarization offers exciting opportunities for diagnostic applications. However, their hyperpolarization via parahydrogen remains challenging as specific catalytic interactions are required, which are difficult to tune due to the large size of the biomolecule and its insolubility in organic solvents. Herein, we show the unprecedented hyperpolarization of the cancer-targeting DNA aptamer AS1411. By screening different molecular motifs for an unsaturated label in nucleosides and in DNA oligomers, we were able to identify structural prerequisites for the hyperpolarization of AS1411. Finally, adjusting the polarity of AS1411 by complexing the DNA backbone with amino polyethylene glycol chains allowed the hydrogenation of the label with parahydrogen while the DNA structure remains stable to maintain its biological function. Our results are expected to advance hyperpolarized molecular imaging technology for disease detection in the future.

Silicon Carbamates by CO2 Fixation: Brønsted Acid Labile Precursor of a Lewis Superacid.

Treatment of Lewis superacidic Si(catCl)2(MeCN)2 and tetramethylpiperidine (TMP) or hexahydropyrimidopyrimidine (hppH) with CO2 leads to an FLP-type formation of silicon carbamates. The employed Lewis base determines the hapticity at silicon and the reactivity of the carbamates in subsequent transformations. Upon treatment with a Brønsted acid, the carbamates liberate CO2 and reactivate the Lewis superacidic behavior of 1. Hence, the CO2 fixation products serve as valuable surrogates for Si(catCl)2 that circumvent its insolubility in organic solvents. Quantum chemical computations support all of the experimental observations.

Network Formation and Physical Properties of Epoxy Resins for Future Practical Applications.

Epoxy resins are used in various fields in a wide range of applications such as coatings, adhesives, modeling compounds, impregnation materials, high-performance composites, insulating materials, and encapsulating and packaging materials for electronic devices. To achieve the desired properties, it is necessary to obtain a better understanding of how the network formation and physical state change involved in the curing reaction affect the resultant network architecture and physical properties. However, this is not necessarily easy because of their infusibility at higher temperatures and insolubility in organic solvents. In this paper, we summarize the knowledge related to these issues which has been gathered using various experimental techniques in conjunction with molecular dynamics simulations. This should provide useful ideas for researchers who aim to design and construct various thermosetting polymer systems including currently popular materials such as vitrimers over epoxy resins.

Nitroacetonitrile and Its Synthetic Equivalents.

Nitroacetonitrile (NAN) serves as a cyano(nitro)methylating agent facilitating the construction of polyfunctionalized compounds; however, its explosive property is a significant drawback in terms of practical handling. Alkali metal salts of NAN are thermally stable, but their insolubility in organic solvents restricts their use as a synthetic reagents. On the contrary, dipyrrolidinium cyano-aci-nitroacetate is soluble in common organic solvents and thermally stable, allowing for its use as an alternative synthetic equivalent of nitroacetonitrile for the construction of polyfunctionalized frameworks via cyano(nitro)methylation.

Advances in the Modification of Starch via Esterification for Enhanced Properties

Starch, a renewable polysaccharide, has attracted growing interest as an alternative industrial feedstock due to its biodegradability, low cost, and readily available hydroxyl (–OH) group, thereby according it the potential of possible modification. Despite its environmental suitability, several factors such as brittleness, sensitivity to enzymes and acids, insolubility in organic solvents etc., have been reported to limit its application as feedstock in some industrial processes. However, techniques of chemical modification aimed towards overcoming these shortcomings have been reported to proceed via substitution, degradation or cross-linking. The degree of substitution (DS) for modified starch is targeted within high (1.5–3), medium (0.2–1.5), and low (0.01–0.2). This is as it relates to their application as thickener or stabilizer in food industry, development of thermoplastic and biodegradable materials. Impact of reaction medium and catalyst type are examined as it affects the degree of substitution. During esterification, the reaction either occurs on the whole starch chains to form conventional starch esters or occurs at the outer surface of the starch molecule, leaving the internal crystalline structure intact. Consequently, the degree of rupturing with subsequent esterification of starch has been reported to be dependent on the agent used, hence classifying the esters formed as organic or inorganic. Therefore, this review examines various findings targeted at starch modification with a direct focus on improving the degree of substitution (DS) via double esterification.

Photoswitchable Solubility of Fullerene-Doped Polymer Thin Films

Controlling polymer film solubility is of fundamental and practical interest and is typically achieved by synthetically modifying the polymer structure to insert reactive groups. Here, we demonstrate that the addition of fullerenes or its derivatives (C60 or phenyl-C61-butyric acid methyl ester, PCBM) to polymers, followed by ultraviolet (UV) illumination can change the film solubility. Contrary to most synthetic polymers which dissolve in organic solvents but not in water, the fullerene-doped polymer films (such as polystyrene) can dissolve in water, yet remain stable in organic solvents. This photoswitchable solubility effect is not observed in either film constituents individually and derives from a synergy of photochemistries. Firstly, polymer photooxidation generates macroradicals which crosslink with radical-scavenging PCBM, thereby contributing to the films' insolubility in organic solvents. Secondly, light exposure enhances polymer photooxidation in the presence of PCBM via the singlet oxygen pathway. This results in polymer backbone scission and formation of photooxidised products which can form hydrogen bonds with water, both contributing to water solubility. Nevertheless, the illuminated doped polymer thin films are mechanically robust, exhibiting significantly increased modulus and density compared to their pristine counterpart, such that they can remain intact, even upon sonication in conventional organic solvents. We further demonstrate the application of this solubility-switching effect in dual tone photolithography, via a facile, economical and environmentally benign solution-processing route made possible by the photoactive nature of polymer-PCBM thin films.

Structural Investigation of Hybrid Peptide Foldamers Composed of α-Dipeptide Equivalent β-Oxy-δ5 -amino Acids.

Due to their equivalent lengths, δ-amino acids can serve as surrogates of α-dipeptides. However, δ-amino acids with proteinogenic side chains have not been well studied because of synthetic difficulties and because of their insolubility in organic solvents. Recently we reported the spontaneous supramolecular gelation of δ-peptides composed of β(O)-δ5 -amino acids. Here, we report the incorporation of β(O)-δ5 -amino acids as guests into the host α-helix, α,γ-hybrid peptide 12-helix and their single-crystal conformations. In addition, we studied the solution conformations of hybrid peptides composed of 1:1 alternating α and β(O)-δ5 -amino acids. In contrast to the control α-helix structures, the crystal structure of peptides with β(O)-δ5 -amino acids exhibit α-helical conformations consisting of both 13- and 10-membered H-bonds. The α,δ-hybrid peptide adopted mixed 13/11-helix conformation in solution with alternating H-bond directionality. Crystal-structure analysis revealed that the α,γ4 -hybrid peptide accommodated the guest β(O)-δ5 -amino acid without significant deviation to the overall helix folding. The results reported here emphasize that β(O)-δ5 -amino acids with proteinogenic side chains can be accommodated into regular α-helix or 12-helix as guests without much deviation of the overall helix folding of the peptides.

Ultraviolet-Assisted Direct Ink Write to Additively Manufacture All-Aromatic Polyimides.

All-aromatic polyimides have degradation temperatures above 500 °C, excellent mechanical strength, and chemical resistance, and are thus ideal polymers for high-temperature applications. However, their all-aromatic structure impedes additive manufacturing (AM) because of the lack of melt processability and insolubility in organic solvents. Recently, our group demonstrated the design of UV-curable polyamic acids (PAA), the precursor of polyimides, to enable their processing using vat photopolymerization AM. This work leverages our previous synthetic strategy and combines it with the high solution viscosity of nonisolated PAA to yield suitable UV-curable inks for UV-assisted direct ink write (UV-DIW). UV-DIW enabled the design of complex three-dimensional structures comprising of thin features, such as truss structures. Dynamic mechanical analysis of printed and imidized specimens confirmed the thermomechanical properties typical of all-aromatic polyimides, showing a storage modulus above 1 GPa up to 400 °C. Processing polyimide precursors via DIW presents opportunity for multimaterial printing of multifunctional components, such as three-dimensional integrated electronics.

Low Density, Thermally Stable, and Intrinsic Flame Retardant Poly(bis(benzimidazo)Benzophenanthroline‐dione) Sponge

AbstractLow density (≤13.9 mg cm−3), compressible poly(bis(benzimidazo)benzophenanthroline‐dione) (BBB) sponges with high temperature resistance are reported. The processing of BBB is limited due to its insolubility in organic solvents and infusibility. Therefore, the sponges are made in two steps: first, the BBB fibers are prepared by electrospinning the starting monomers with a template polymer followed by polycondensation of monomers on solid fibers at high temperature. In the second step, the BBB fibers are mechanically cut and self‐assembled from a dispersion during freeze‐drying. The use of poly(vinyl alcohol) is critical in getting self‐assembled hierarchically double‐pore‐structured, mechanically stable sponges. The sponges show very high pyrolytic stability, high compressibility (more than 92% recovery after 50% compression), very low thermal conductivity (0.028–0.038 W mK−1), and high oil absorption capacity.

Thixotropic Supramolecular Pectin-Poly(Ethylene Glycol) Methacrylate (PEGMA) Hydrogels.

Pectin is an anionic, water-soluble polymer predominantly consisting of covalently 1,4-linked α-d-galacturonic acid units. This naturally occurring, renewable and biodegradable polymer is underutilized in polymer science due to its insolubility in organic solvents, which renders conventional polymerization methods impractical. To circumvent this problem, cerium-initiated radical polymerization was utilized to graft methoxy-poly(ethylene glycol) methacrylate (mPEGMA) onto pectin in water. The copolymers were characterized by 1H nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), and used in the formation of supramolecular hydrogels through the addition of α-cyclodextrin (α-CD) to induce crosslinking. These hydrogels possessed thixotropic properties; shear-thinning to liquid upon agitation but settling into gels at rest. In contrast to most of the other hydrogels produced through the use of poly(ethylene glycol) (PEG)-grafted polymers, the pectin-PEGMA/α-CD hydrogels were unaffected by temperature changes.

Isolation and Structure Determination of a Missing Endohedral Fullerene La@C70 through In Situ Trifluoromethylation

AbstractD5h‐symmetric fullerene C70 (D5h‐C70) is one of the most abundant members of the fullerene family. One longstanding mystery in the field of fullerene chemistry is whether D5h‐C70 is capable of accommodating a rare‐earth metal atom to form an endohedral metallofullerene M@D5h‐C70, which would be expected to show novel electronic properties. The molecular structure of La@C70 remains unresolved since its discovery three decades ago because of its extremely high instability under ambient conditions and insolubility in organic solvents. Herein, we report the single‐crystal X‐ray structure of La@C70(CF3)3, which was obtained through in situ exohedral functionalization by means of trifluoromethylation. The X‐ray crystallographic study reveals that La@C70(CF3)3 is the first example of an endohedral rare‐earth fullerene based on D5h‐C70. The dramatically enhanced stability of La@C70(CF3)3 compared to La@C70 can be ascribed to trifluoromethylation‐induced bandgap enlargement.

Isolation and Structure Determination of a Missing Endohedral Fullerene La@C70 through In Situ Trifluoromethylation.

D5h-symmetric fullerene C70 (D5h-C70) is one of the most abundant members of the fullerene family. One longstanding mystery in the field of fullerene chemistry is whether D5h-C70 is capable of accommodating a rare-earth metal atom to form an endohedral metallofullerene M@D5h-C70, which would be expected to show novel electronic properties. The molecular structure of La@C70 remains unresolved since its discovery three decades ago because of its extremely high instability under ambient conditions and insolubility in organic solvents. Herein, we report the single-crystal X-ray structure of La@C70(CF3)3, which was obtained through in situ exohedral functionalization by means of trifluoromethylation. The X-ray crystallographic study reveals that La@C70(CF3)3 is the first example of an endohedral rare-earth fullerene based on D5h-C70. The dramatically enhanced stability of La@C70(CF3)3 compared to La@C70 can be ascribed to trifluoromethylation-induced bandgap enlargement.

Dilithium Benzenediacrylate As Organic Electrode Material: Life, Death and Rise of the Lithium Phoenix

Organic materials issued from biomass could constitute a viable option as replacements for inorganic materials in Li-ion battery electrodes. Due to their low-cost production, recyclability and structural diversity, many organic materials have been investigated as electrodes for Li-ion cells, such as organic sulfurs, nitroxide radicals, conjugated carbonyl derivatives and disulfides [1,2]. Conjugated carboxylates have become the perhaps most promising type of organic electrode material due to their high theoretical capacity, fast reaction kinetics and structural diversity [3]. The example chosen for this study is dilithium trans-trans benzenediacrylate, an organic material with a practical capacity of approx. 200 mAh*g-1 and an average potential of 1.2 V vs Li+/Li0 [4]. We have previously reported on several properties of this material and its cycling behavior in half cells [5]. Due to that this compound is easily soluble in water and insoluble in organic solvents (such as the carbonates used as electrolytes), a method of extraction from spent cells and recycling of this compound has been used with promising results. This method is based on the extraction of the active material by dissolution in water followed by filtrations/drying sequences. Its insolubility in organic solvents allows separation of the active material from other components by a washing step [6], after which it can be combusted to Li2CO3. This method is also dependant on the choice of battery electrolyte, and better performance can be observed using an electrolyte system with stability in presence of water. According to these properties, an idealized recycling process can be obtained, presented in Fig. 1. This facilitates the recycling of lithium from the battery, and a new cell can be constructed from the ashes of a spent device, with only addition of new biomass-derived materials – a Phoenix-like transformation. Fig. 1. Idealized recycling process of organic electrode materials from spent batteries. So far, this method has mainly been applied to prototype cells in which the organic compound was cycled vs. Li or LFP. Here, a similar method is presented using pouch cells, with addition of binders whose separation from active material pose a problem, not least if water soluble components such as CMC (carboxymethylcellulose) are used. Therefore, additional steps in the procedure have been included to better separate the binder from the active material. Moreover, the cycling behavior of the active organic material in full cells will be presented, as well as recycling strategies from spent batteries.

Using Stable Radicals To Protect Pentacene Derivatives from Photodegradation

A radical solution: The photochemical instability and insolubility in organic solvents of pentacene derivatives prevent their use in molecular electronics. These issues were solved by using pentacene derivatives with stable radicals (Y=radical moiety, 1 a and 2 a) that have a lifetime of 2077 min in organic solvents under ambient light. The corresponding nonradical pentacene derivatives (Y=radical precursor, 1 b and 2 b) decay on exposure to light. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Immobilization of β-Cyclodextrin as Insoluble β-Cyclodextrin Polymer and Its Catalytic Performance

Insoluble β-cyclodextrin polymers were prepared from β-cyclodextrin (β-CD) using epichlorohydrin (EPI) as crosslinking agent under basic conditions. The polymers were characterized by Fourier Transform Infrared (FTIR), Thermogravimetry (TG), X-ray diffraction (XRD) and TG-FTIR. The results demonstrated that the polymerization between EPI and β-CD indeed occurred, and a number of CD rings were interconnected to form a three-dimensional network. Moreover, different factors influencing the polymerization, e.g. molar ratio of EPI to β-CD, the concentration of NaOH and reaction temperature, have been investigated. The polymer prepared under the optimal conditions (the molar ratio EPI: β-CD of 44, the NaOH concentration 50% in mass, and the temperature at 65 °C) showed excellent thermal stability and insolubility in organic solvents or strong acid/base. In addition, the β-cyclodextrin polymers also presented high catalytic activity for aqueous oxidation of benzyl alcohol with hypochlorite as oxidant.

Silica Chloride-Catalyzed Microwave-Assisted Efficient and Selective One-Pot Synthesis of Amides from Aldehydes

The amide function is ubiquitous in organic and biological chemistry. Amides are used as protecting groups in organic synthesis as they offer the advantages of very good stability to a wide range of conditions. They play an important role as technical polymers, pharmaceuticals, agrochemicals, peptides and proteins. Amides are formed by the reaction of a carboxylic acid with an amine. The other alternative methods include Schotten-Baumann reaction, Beckmann rearrangement, Willgerodt reaction, Ugi reaction, Chapmann rearrangement, dehydrogenative acylation. Conversion of aldoximes to amides is present in the literature. We also have carried out the inter-conversion of amides to nitriles and vice versa. In recent years, solid-phase synthesis has become one of the most important tools in organic synthesis. Silica chloride is prepared by treating SOCl2 with silica gel (Scheme 1). Due to its insolubility in organic solvents and the presence of labile Si-Cl bond which gives rise to Lewis acid centres, and nucleophile accepting property, it can be used for different purposes. SiO2-Cl catalyzed protection of carbonyl compounds and synthesis of amidoalkyl-2-naphthols are well known reactions. Silica chloride is also used for the preparation of other silica bonded reagents. The extent of chlorination of the silica surface was determined by taking 1 g SiO2-Cl in 25 mL boiled distilled water and titrated against 0.1N NaOH (9.3 mL). The amount of immobilized Cl has been found to be 0.93 miliquivalents/ g SiO2. 3

Self-crosslinked anion exchange membranes by bromination of benzylmethyl-containing poly(sulfone)s for direct methanol fuel cells

A series of novel anion exchange membranes based on poly(arylene ether sulfone) were fabricated. And the synthesized 1, 1, 2, 3, 3-pentamethylguanidine was used as a hydrophilic group. Bromination reaction rather than chloromethylation was used for the preparation of target conductive polymers. Fourier transform infrared spectroscopy (FTIR), 1H NMR and mass spectrometry (MS) were used to characterize the as-synthesized polymers. The ratio of hydrophilic to hydrophobic monomers was varied to study the structure-property of the membranes. The performance of the membrane with both hydrophilic/hydrophobic segments was improved over the membrane with sole hydrophilic segments. The self-crosslinking structure of the as-prepared membranes is partly responsible for their very low methanol permeability with the minimum of 1.02 × 10−9 cm−2⋅S−1 at 30 °C and insolubility in organic solvents considered. The structural dependence of water uptake is in the range of 25–87%. The as-prepared membranes did not suffer from serious membrane swelling. The ionic exchange capacity (IEC) reached a maximum of 1.21 mmol⋅g−1. The ionic conductivity of the membrane in deionized water is 6.00 and 13.00 × 10−2 S⋅cm−1 at 30 and 80 °C respectively.