Acrylonitrile Research Articles

Synthesis and thermal behavior of acrylonitrile/guanidine crotonate copolymer for carbon fiber precursor

AbstractThe thermal oxidation stabilization of polyacrylonitrile (PAN) copolymer is a highly exothermic process. It significantly impacts the quality of the finished PAN‐based carbon fiber, which is often addressed by adding appropriate comonomers. This paper synthesized guanidine crotonate (GCA) as a comonomer and copolymerized with acrylonitrile (AN) to prepare P(AN‐GCA). DSC analysis revealed that when compared to PAN and P(AN‐CA) copolymers, the initial exothermic temperature, maximum exothermic heat flux, and heat flux of P(AN‐GCA) copolymer were greatly reduced. FT‐IR spectroscopy showed that the degree of pre‐oxidation increased with the increasing comonomer GCA content, indicating that the addition of comonomer GCA could promote PAN pre‐oxidation cyclization and improve the copolymer's degree of pre‐oxidation. The activation energies of PAN and P(AN‐GCA) were 160 and 126 KJ/mol, respectively. It was shown that the addition of GCA could effectively reduce the activation energy of the cyclization reaction of the polymer while simultaneously promoting it. TGA analysis shows that the introduction of GCA improves the copolymer's thermal stability, and the yield at 800°C is more than 54%, which is at least 19% higher than PAN homopolymer. P(AN‐GCA) has the potential to be carbon fiber precursor.

Microplastic Transport and Accumulation in Rural Waterbodies: Insights from a Small Catchment in East China.

Microplastic (MP) pollution in agricultural ecosystems is an emerging environmental concern, with limited knowledge of its transport and accumulation in rural waterbodies. This study investigates the distribution and sources of MP in drainage ditches influenced by pond connectivity, land use, and soil properties within a small catchment in Nanjing, East China. Sediment was collected from ditches in 18 sites across forest, agricultural, horticultural, and urban areas. Using laser-directed infrared spectroscopy (LDIR), 922 MP particles were identified. Six materials were dominant: fluororubber (FR), polyethylene terephthalate (PET), polyurethane (PU), acrylonitrile (ACR), chlorinated polyethylene (CPE), and polyethylene (PE). MP concentrations varied by land use and pond connectivity, with ditches above ponds exhibiting higher counts (1700 particles/kg) than those below (1050 particles/kg), indicating that ponds act as MP sinks. The analysis revealed site-specific MP sources, with FR linked to road runoff and PET associated with agricultural practices. Correlations between MP shape and soil properties showed that more compact and filled shapes were more commonly associated with coarser soils. PE particle size was negatively correlated with organic matter. This study highlights the need for targeted strategies to reduce MP pollution in rural landscapes, such as reducing plastic use, ditch maintenance, and improved road runoff management.

Synthesis and Characterization of cellulose-derived superabsorbent hydrogel and its applications in the treatment of wastewater containing heavy metal ions

A cellulose xanthate (CX) based polymer hydrogel has been synthesized using free radical graft polymerization technique. Two monomers Acrylic Acid (AA) and Acrylonitrile (AN) were reacted with cellulose xanthate to synthesize the desired hydrogel CX-g-poly(AA-co-AN). The synthesized hydrogel has been characterized by various techniques viz. Thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV), Field emission scanning electron microscope (FESEM) and Point zero charge (PZC). This hydrogel has been employed for the removal of toxic metal ions from wastewater. The maximum percentage removal has been found to be 97.5 (±4.87)% for Cu2+ ions and 96.1 (±4.80)% for Co2+ ions under optimum pH 6. The calculated adsorption capacities have been found to be 330.03 (±35.3) mg/g for Cu2+ ions and 325.73 (±22.4) mg/g for Co2+ ions using the Langmuir Adsorption isotherm model. The thermodynamic parameters depicted that the process was endothermic, and spontaneous. The adsorption kinetics data shows excellent fit with pseudo-second-order kinetic model. The synthesized hydrogel exhibits a high swelling ratio of 846.85 (±42.36) g/g and retention ratio of 50.12 (±2.50) % in distilled water. Also, the synthesized hydrogel showed good reusability, exhibiting percentage removal 83.2% for Cu2+ ions and 81.3% for Co2+ ions in the fifth cycle.

In Situ Formation of Acidic Comonomer during Thermal Treatment of Copolymers of Acrylonitrile and Its Influence on the Cyclization Reaction.

Binary and ternary copolymers of acrylonitrile (AN), tert-butyl acrylate (TBA), and n-butyl acrylate (BA) are synthesized through conventional radical polymerization in DMSO in the presence of 2-mercaptoethanol. The thermal behavior of binary and ternary copolymers is studied under argon atmosphere and in air. It is demonstrated that the copolymers of AN contain 1-10 mol.% of TBA split isobutylene upon heating above 160 °C, resulting in the formation of the units of acrylic acid in the chain. The carboxylic groups formed in situ are responsible for the ionic mechanism of cyclization, which starts at lower temperatures compared with pure polyacrylonitrile (PAN) or AN copolymer with BA. The activation energy of cyclization through ionic and radical mechanisms depends on copolymer composition. For the ionic mechanism, the activation energy lies in the range ca. 100-130 kJ/mole, while for the radical mechanism, it lies in the range ca. 150-190 kJ/mole. The increase in the TBA molar part in the copolymer is followed by faster consumption of nitrile groups and the evolution of a ladder structure in both binary and ternary copolymers. Thus, the incorporation of a certain amount of TBA in PAN or its copolymer with BA allows tuning the temperature range of cyclization. This feature seems attractive for applications in the production of melt-spun PAN by choosing the appropriate copolymer composition and heating mode.

Systematic Investigation on the Swelling Response and Oil Resistance of NBR Using the Prediction Models Determined by the Modified Flory-Huggins Interaction Parameter.

The equilibrium swelling test was employed to determine the swelling response of Nitrile Butadiene Rubber (NBR) with various acrylonitrile (ACN) contents, and the three-dimensional solubility parameter (HSP) and modified Flory-Huggins interaction parameter (χHSP) were used to establish the prediction model of the oil-resistant property. The results indicate that the energy difference (Ra) between NBR and solvents calculated by HSP values can be correlated with the swelling response qualitatively with an inversed "S-shape", and high swelling response occurs at Ra < 8 MPa1/2 for NBR. For the purpose of establishing the prediction model, the new modified χHSP value has been calculated and fitted with the swelling response using exponential and logarithmic fittings, respectively. Two prediction models considering all the possible influencing factors have been obtained to determine the swelling response and oil resistance of NBR-based rubber products in bio-fuels, represented by the bio-diesel and IRM 903 test oil in this work. The swelling response of NBR can be evaluated precisely, and high swelling regions can be predicted and avoided in the new emerging fuels through the prediction models. Thus, the oil resistance of NBR-based rubber products, such as seals, holes and gaskets can be well predicted now.

Fabrication of Flexible Wearable Mechanosensors Utilizing Piezoelectric Hydrogels Mechanically Enhanced by Dipole-Dipole Interactions.

Conductive hydrogels have been increasingly employed to construct wearable mechanosensors due to their excellent mechanical flexibility close to that of soft tissues. In this work, piezoelectric hydrogels are prepared through free radical copolymerization of acrylamide (AM) and acrylonitrile (AN) and further utilized in assembling flexible wearable mechanosensors. Introduction of the polyacrylonitrile (PAN) component in the copolymers endows the hydrogels with excellent piezoelectric properties. Meanwhile, significant enhancement of mechanical properties has been accessed by forming dipole-dipole interactions, which results in a tensile strength of 0.51 MPa. Flexible wearable mechanosensors are fabricated by utilizing piezoelectric hydrogels as key signal converting materials. Self-powered piezoelectric pressure sensors are assembled with a sensitivity (S) of 0.2 V kPa-1. Additionally, resistive strain sensors (gauge factor (GF): 0.84, strain range: 0-250%) and capacitive pressure sensors (S: 0.23 kPa-1, pressure range: 0-8 kPa) are fabricated by utilizing such hydrogels. These flexible wearable mechanosensors can monitor diverse body movements such as joint bending, walking, running, and stair climbing. This work is anticipated to offer promising soft materials for efficient mechanical-to-electrical signal conversion and provides new insights into the development of various wearable mechanosensors.

Insights of mechanism and kinetics of acrylonitrile aqueous precipitation polymerization

Aqueous precipitation polymerization is commonly used in the industry due to its efficient heat dissipation, reaction stability and production flexibility. However, its mechanisms and kinetics are still partially unclear. The ammonium persulfate-ammonium sulfite monohydrate (APS-AS) initiated aqueous phase precipitation polymerization of acrylonitrile (AN) at low concentration was deeply investigated, with the APS initiation system as a control. The apparent kinetic equations for the APS and APS-AS initiation systems were determined to be Rp= K[AN]1.706[(NH4)2S2O8]0.704 and Rp= K[AN]3[(NH4)2S2O8]0.704[(NH4)2S2O3]−1.055, respectively. Monitoring AN distribution in the aqueous and polyacrylonitrile (PAN) phases revealed a rapid transition of the reaction site from the aqueous phase to the PAN phase following polymer precipitation. Zeta potential and primary particle number exposed that the nucleation site disparities between initiation systems led to different predominant factors affecting the polymerization rate. The change in molecular weight during polymerization had a maximum due to its dependence on the monomer concentration. The crystallinity of the product initially increased during polymerization, then decreased and eventually stabilized. Scanning electron microscopy (SEM) revealed that the diameter of the internal particles was larger, while the surface particles were smaller after coagulation. These findings offer crucial insights for optimizing aqueous precipitation polymerization and PAN particle property control.

Survey of complex organic molecules in starless and pre-stellar cores in the Perseus molecular cloud

ABSTRACT Cold ($\sim$10 K) and dense ($\sim 10^{5}$ cm$^{-3}$) cores of gas and dust within molecular clouds, known as starless and dynamically evolved pre-stellar cores, are the birthplaces of low-mass (M$\le$ few M$_\odot$) stars. As detections of interstellar complex organic molecules, or COMs, in starless cores has increased, abundance comparisons suggest that some COMs might be seeded early in the star formation process and inherited to later stages (i.e. protostellar discs and eventually comets). To date observations of COMs in starless cores have been limited, with most detections reported solely in the Taurus molecular cloud. It is therefore still a question whether different environments affect abundances. We have surveyed 35 starless and pre-stellar cores in the Perseus molecular cloud with the Arizona Radio Observatory (ARO) 12 m telescope detecting both methanol, CH$_3$OH, and acetaldehyde, CH$_3$CHO, in 100 per cent and 49 per cent of the sample, respectively. In the sub-sample of 15 cores where CH$_3$CHO was detected at $\gt 3\sigma$ ($\sim$18 mK) with the ARO 12 m, follow-up observations with the Yebes 40 m telescope were carried out. Detections of formic acid, t-HCOOH, ketene, H$_2$CCO, methyl cyanide, CH$_3$CN, vinyl cyanide, CH$_2$CHCN, methyl formate, HCOOCH$_3$, and dimethyl ether, CH$_3$OCH$_3$, are seen in at least 20 per cent of the cores. We discuss detection statistics, calculate column densities, and compare abundances across various stages of low-mass star formation. Our findings have more than doubled COM detection statistics in cold cores and show COMs are prevalent in the gas before star and planet formation in the Perseus molecular cloud.

RELAXATION BEHAVIOR OF 3D PRINTED NBR-BASED RUBBER O-RINGS AS THE INNER PART OF ROD SEALS

ABSTRACT The viscoelastic properties of rubber polymer–based compounds are crucial for further applications but challenging in the manufacturing process using additive manufacturing techniques. The fact that the first layer is attached to the printing bed restricts free relaxation after extrusion and the part shows a strong contraction along the printing direction after release and especially after vulcanization. In this study, the molar mass distribution and the acrylonitrile (ACN) content of an NBR-based compound for the fabrication of O-rings for rod seal applications were varied to demonstrate the different degree of contraction resulting from three-dimensional printing. An ACN content of 34% and an average molar mass of 2.47·105 g·mol−1 with a dispersity index of 2.6 was found to be a suitable compromise between the degree of contraction and compression set as a criterion for the application as O-ring as the inner part of rod seals.

Theoretical investigation of interstellar 3-pyrroline: formation and, rotational and vibrational spectroscopy

ABSTRACT The recent detection of CN-functionalized aromatics partly addresses the long-standing mystery of the apparent absence of five- and six-membered rings in interstellar environments. Nitrogen (N)-heterocycles, which are crucial as the fundamental structures of nucleobases, have been a focus of these aromatic searches due to their biological significance. Although N-heterocycles have not been conclusively detected in astrophysical environments, their presence in chondrites and meteorites signifies their interstellar and circumstellar connection. Precise spectral data identify the unique signatures of molecules, confirming their presence in space. In this light, this work reports an extensive computational investigation on interstellar 3-pyrroline, a five-membered ring N-heterocycle. This includes an alternative formation route in cold interstellar environments and highly accurate rotational and vibrational spectroscopy. The results indicate that 3-pyrroline can form on dust grain surfaces from vinyl cyanide, as its formation from pyrrole through double hydrogenation may lead to the formation of pyrrole itself via an H2-abstraction process. 3-Pyrroline’s rotational transition at 52.3 GHz offers a potential tool for its detection in cold interstellar regions. Additionally, the strongest infrared (IR) features of 3-pyrroline at 16.09 and $\sim$3.50 $\mu$m are observable with JWST. The provided data are crucial for laboratory identification and future interstellar observations of 3-pyrroline at both radio and IR wavelengths.

Accelerated Development and Optimization of Adiponitrile Production via Kolbe Electrolysis of Biomass-Derived Precursors

Environmental and societal pressures are demanding a transition from fossil-based resources to renewable and sustainable feedstocks for the production of materials. In this context, biomass streams emerge as scalable candidates for creating sustainable chemicals. Electrocatalytic transformation of biomass can facilitate the production of chemicals under mild conditions and can be easily integrated with renewable energy sources. These transformations could lead to the production of sustainable monomers and polymers from biomass, significantly enhancing the sustainability of plastics production. Amongst a large number of plastics manufactured by the chemical industry, Nylon 6,6 is one of the most important fossil-derived polymers for the production of high-performance textiles and structural materials. Central to Nylon 6,6 production is adiponitrile (ADN), predominantly synthesized via energy-intensive thermochemical processes. An alternative route, electrochemical hydrodimerization of acrylonitrile (AN), although successful, still depends on fossil feedstocks. A promising sustainable source for ADN is renewable glutamic acid, derived from hydrolysis of waste proteins.1,2 This process involves transforming glutamic acid to 3-cyanopropanoic acid (CPA) and then to ADN through Kolbe electrolysis, a reaction with a historical background and multiple pathways. Our study utilizes an electrochemical reaction engineering approach to examine the Kolbe electrolysis of CPA to ADN and AN, focusing on a hierarchical research methodology. This approach allowed us to simultaneously accelerate the exploration of numerous reaction parameters while also conducting detailed studies under optimal conditions. This method has enabled us to gain deeper insights into the factors controlling reaction selectivity. We discovered that platinum electrodes favor ADN formation, with selectivity increasing at higher current densities. Optimal CPA concentrations, the presence of larger alkali cations, solvent composition, and controlled pH levels significantly influence ADN production, reducing side reactions such as the oxygen evolution reaction (OER). When using graphite electrodes, an increase in AN production was observed, with the solvent composition playing a crucial role in determining the rate of ADN formation. Our investigation has led to a deeper understanding of the electrochemical conversion of CPA to ADN, revealing key parameters that influence reaction selectivity and rate. The insights obtained from this study are not only pivotal for the specific case of ADN production but also have broader implications for a range of electrochemical decarboxylation reactions. The hierarchical research approach employed here demonstrates its potential for speeding the development of sustainable electrochemical processes. Our insights and methodology used for the electrosynthesis of ADN from biomass-derived feedstocks can be deployed to the deployed to the development of other biomass transformations advancing our ability to produce essential chemicals sustainably.

(Invited) Electrochemical Engineering Approaches for High-Performing Electrosynthesis of Polymer Precursors

The chemical industry accounts for ~5% of the US energy utilization and >30% of the US energy-derived industrial CO2 emissions. Amongst these processes, the production of organic chemical commodities, many of which are used as polymer precursors, account for the majority of the energy utilization (>1200 TBTU/y). The electrification of these processes via the implementation of electro-organic reactions could accelerate the decarbonization of the chemical industry, and bring additional sustainability advantages over their thermo-chemical counterparts. Currently, however, two major challenges prevent the deployment of electro-organic reactions: their low selectivity and their low production rates. To circumvent these barriers, our group deploys electrochemical reaction engineering principles to engineer electrode/electrolyte interfaces and design high-performing electro-organic processes. In this presentation, I will discuss how we implement this approach to understand and improve the performance of electro-organic reactions for the production of large-scale precursors for the production of Nylon 6,6 and polyethylene.The production of Nylon 6,6 involves the step-growth polymerization of 1,6-hexanediamine (HMDA) with adipic acid. HMDA is currently produced by the hydrogenation of adiponitrile (ADN). Here, I will present our insights into the electrohydrodimerization of acrylonitrile (AN) to adiponitrile (ADN). This is one of the largest electro-organic reaction deployed in industry and serves as a model process for the development of practical organic electrochemical processes. Our investigations on ADN uncovered relationships between the microenvironment at and near the electrical double layer (EDL) and reaction performance metrics (i.e., selectivity, efficiency, and productivity). I will discuss general guidelines for electrolyte formulation, dynamic electrochemical operation, the implementation of convective forces to mitigate transport limitations, ultimately leading in the conversion of AN to ADN at Faradaic efficiencies >80% and current densities of 100’s mA/cm2. Our learnings on ADN electrosynthesis helped us to engineer the electrocatalytic hydrogenation of ADN to HMDA, achieving the highest reported selectivity to date for this reaction (>95%). I will also show how similar electrochemical engineering approaches allowed us to elucidate factors that control performance in the electrochemical production of ADN from glutamic acid, an abundant and inexpensive bio-based feedstock, and of ethylene from bio-derived propionic acid. Through our studies, we aim to electrify and bring sustainability to chemical manufacturing, one reaction at a time.

Polymerized Acrylonitrile Artificial SEI for Long-Life Li-Metal Battery and Enhanced Stability for Li/Li10GeP2S12 Interface

Lithium metal anode batteries have attracted significant attention as a promising energy storage technology, offering a high theoretical specific capacity and low electrochemical potential. Utilizing lithium metal as the anode material can substantially increase energy density compared to conventional lithium-ion batteries. However, the practical application of lithium metal anodes has encountered notable challenges, primarily due to the formation of dendritic structures during cycling. These dendrites pose safety risks and degrade battery performance. Addressing these challenges necessitates the development of a reliable and effective protection layer for lithium metal. This study presents a cost-effective and convenient method to produce lithium metal protective layers by creating ex-situ polymer layers using acrylonitrile (AN). This method extends the lifetime of lithium metal anodes by a remarkable factor of six under high current (1 mA/cm²) cycling conditions. While the cycle life of bare lithium metal is approximately 150 hours under high current conditions, AN-treated lithium metal anodes exhibit an impressive longevity of over 900 hours.Furthermore, with the increasing attentions on solid-state electrolytes – which address the safety concerns and energy density limitations associated with conventional liquid electrolytes in lithium-ion batteries, the interface between Li metal and solid-state electrolytes has been the major challenges. For example, Li10GeP2S12 (LGPS) stands out among these solid electrolyte materials, boasting high ionic conductivity (1 x 10⁻² S cm⁻¹). Nonetheless, the severe instability of the interface between lithium metal anodes and solid electrolytes, including dendrite formation and electrolyte degradation, hindering their practical implementation. This work also goes deeply to explore the stability and performance of Li | LGPS systems by utilizing a polymerized acrylonitrile interfacial. By elucidating the mechanisms governing the interfacial layers, this low-cost fabrication of AN-treated lithium metal holds significant potential for advancing the commercialization of future lithium-metal batteries, surpassing the capabilities of traditional lithium-ion batteries.

Structure and thermal properties of acrylic copolymer gels: effect of composition and cross-linking method

Two approaches to the synthesis of hydrogels based on polyacrylamide (pAAm) with copolymers were compared in the paper—traditional chemical cross-linking and physical cross-linking with montmorillonite (MMT). The main aim of the work was to find an adequate replacement of the chemical toxic cross-linking agent MBAAm (N,N'-methylene-bis-acrylamide) by using non-toxic—natural clay MMT for synthesis of pAAm gels, which are planned to be used as soil conditioners. A series of hydrogels based on acrylic monomers (acrylamide (AAm), acrylonitrile (AN), acrylic acid (AA)) physically cross–linked by MMT and chemically cross-linked were synthesized. For the synthesized gels, the influence of the synthesis method on the formation of the structure and the mechanism of thermal destruction in the presence of air was analyzed using a set of physicochemical methods: FTIR, XRD, SEM, DSC and TG/DTG. According to FTIR and XRD data, pAAm-MMT and pAAm-AN-MMT samples formed an intercalated/exfoliated structure, whereas pAAm-AA-MMT had an intercalated structure. The endothermic reaction of decomposition of xerogels based on acrylic polymers with and without MMT was observed using DSC and derivative thermogravimetry analyses, coupled with measurement of FTIR spectra of volatile products of thermolysis. All studied composites were relatively thermoresistant, which had three distinct regions of phase transitions and their thermal decomposition occurred at a temperature range 310–465 °C.Graphical

Hitting two birds with one stone: DPAC derivatization with o-carborane resulted in improved photochemical stability and enhanced sensing performance

Innovative design of sensing materials is pivotal for the development of high-performance fluorescence film sensors (FFSs). In this work, we combined one or two o-carboranyl units into the skeleton of N,N′-diphenyldihydrodibenzo[a,c]phenazine (DPAC), a well-known fluorophore, and obtained two new DPAC derivatives, CbDPAC-Ph and bis-CbDPAC-Ph. We found incorporation of o-carborane not only enriches the stacking of DPAC, enhancing photostability and increasing the Stokes shift, but also facilitates analyte mass transfer in the fluorescent active layer due to increased molecular channels. Further studies revealed that the FFSs based on bis-CbDPAC-Ph exhibit outstanding cyclic stability and are highly sensitive to acrylonitrile (ACN), with a detection limit of 22 ppb, significantly lower than the 450-ppb threshold value recommended by the Risk Assessment Committee (RAC) of Europe for workplaces. Moreover, with a response time within 2 s and a full recovery time of less than 2 min, this device shows promising potential for developing into a portable ACN detector.

Theoretical studies on the aqueous phase and graphene heterogeneous degradation of acrylamide and acrylonitrile by HO, ClO, and BrO radicals

The newly discovered ClO• and BrO• contribute to pollutant degradation in advanced oxidation processes, while acrylamide (AM) and acrylonitrile (ACN) are always the focus of scientists concerned due to their continuous production and highly toxic effects. Moreover, various particles with a graphene-like structure are the companions of AM/ACN in dry/wet sedimentation or aqueous phase existence, which play an important role in heterogeneous oxidation. Thus, this work focuses on the reaction mechanism and environmental effect of AM/ACN with ClO•/BrO•/HO• in the water environment under the influence of graphene (GP). The results show that although the reactivity sequence of AM and ACN takes the order of with HO• > with BrO• > with ClO•, the easiest channel always occurs at the same C-position of the two reactants. The reaction rate constants (k) of AM with three radicals are 2 times larger than that with ACN, and amide groups have a better ability to activate CC bonds than cyanide groups. The existence of GP can accelerate the target reaction, and the k increased by 9–13 orders of magnitude. The toxicity assessment results show that the toxic effect of most products is lower than that of parent compounds, but the environmental risk of products from ClO•/BrO•-adducts is higher than those from HO•-adducts. The oxidative degradation process based on ClO• and BrO• deserves special attention, and the catalytic effect of GP and its derivatives on the oxidation process is non-negligible.

CN and CCH derivatives of ethylene and ethane: Confirmation of the detection of CH3CH2CCH in TMC-1

We present a study of CH3CH2CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN in TMC-1 using the QUIJOTE line survey. We confirm the presence of CH3CH2CCH in TMC-1, which was previously reported as tentative by our group. From a detailed study of the ethynyl and cyanide derivatives of CH2CH2 and CH3CH3 in TMC-1, we found that the CH2CHCCH/CH2CHCN and CH3CH2CCH/CH3CH2CN abundance ratios are 1.5±0.1 and 4.8±0.5, respectively. The derived CH2CHCCH/CH3CH2CCH abundance ratio is 15.3±0.8, and that of CH2CHCN over CH3CH2CN is 48±5. All the single substituted isotopologs of vinyl cyanide have been detected, and we found that the first and second carbon substitutions in CH2CHCN provide a 12C/13C ratio in line with that found for other three-carbon bearing species such as HCCNC and HNCCC. However, the third 13C isotopolog, CH2CH13CN, presents an increase in its abundance similar to that found for HCCCN. Finally, we observed eight b-type transitions of CH2CHCN, and we find that their intensity cannot be fitted adopting the dipole moment µb derived previously. These transitions involve the same rotational levels as those of the a-type transitions. From their intensity, we obtain µb = 0.80±0.03 D, which is found to be in between earlier values derived in the laboratory using intensity measurements or the Stark effect. Our chemical model indicates that the abundances of CH3CH2 CCH, CH3CH2CN, CH2CHCCH, and CH2CHCN observed in TMC-1 can be explained in terms of gas-phase reactions.

RELAXATION BEHAVIOR OF 3D PRINTED NBR-BASED RUBBER O-RINGS AS INNER PART OF ROD SEALS

ABSTRACT The viscoelastic properties of rubber polymer-based compounds are crucial for further applications but challenging in the manufacturing process using additive manufacturing techniques. The fact that the first layer is attached to the printing bed restricts free relaxation after extrusion, that the part shows a strong contraction along the printing direction after release and especially after vulcanization. In this study, the molar mass distribution and acrylonitrile (ACN) content of an NBR-based compound for the fabrication of O-rings for rod seal applications was varied to demonstrate the different degree of contraction resulting from 3D printing. An ACN content of 34% and an average molar mass Mw of 2.47·105 g·mol−1 with a dispersity index D of 2.6 was found to be a suitable compromise between the degree of contraction and compression set as a criterion for the application as O-ring as inner part of rod seals.

Detection of syringic acid in food extracts using molecular imprinted polyacrylonitrile infused graphite electrode

A highly sensitive, cost-effective, and reproducible electrochemical sensor has been developed using acrylonitrile (AN) molecularly imprinted polymer (MIP) over graphite (MIP-AN@G electrode) for the first time to detect phenolic compound, syringic acid (SA), in food extracts. The primary objective of the recognition of specific health-beneficial compounds like SA is to assess the overall quality of fruits and vegetables. Introducing UV–visible (UV–vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM), the characterization of the fabricated MIP-AN@G electrode material has been performed. To investigate the electrode’s analytical characteristics, a tri-electrode system employing differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques was used. Rigorous analysis revealed that the electrode could exhibit high repeatability, high reproducibility, reasonably good stability, and a wide linearity window from 10 μM to 100 μM concentrations with a satisfactory lower limit of SA detection (LOD) of 0.32 μM, and a lower limit of quantification (LOQ) of 1.06 μM. The sensor’s detection competence has been further tested in cauliflower, oregano, and black olives samples, and high accuracies of over 99% were achieved in each case when compared to the high-performance liquid chromatography (HPLC) analysis. Further, the t-test statistical analysis yields satisfactory results for the SA concentrations present in the three real samples.

Microphase Separation 3D Printing of Binary Inorganic Polymer Precursors to Prepare Nanostructured Carbon‐Ceramic Multimaterials

AbstractTraditionally, combining carbon and ceramic materials has been challenging due to their different chemical and physical properties. Despite the development of numerous methodologies for their synthesis, these techniques frequently necessitate intricate, multi‐stage protocols and specialized equipment. This study introduces a novel approach for fabricating nanostructured carbon‐ceramic multimaterials through polymerization‐induced microphase separation 3D printing. By combining inorganic precursors, polycarbosilane, and acrylonitrile (AN) within a photocurable resin, heterogeneous nanostructured materials composed of PAN‐preceramic and sacrificial polymer phases are 3D printed. Upon pyrolysis, PAN‐preceramic domains transformed into a carbon‐ceramic matrix while sacrificial polymer domains thermally decomposed to yield nanoscale voids. The utilization of synchrotron X‐ray spectroscopy and microscopy techniques revealed that the phase compositions and microstructure of the resulting multi‐materials are significantly influenced by the initial composition of the resins. The co‐existence of ceramic and carbon phases within a single 3D printed material brought together a combination of properties from both phases, such as the low thermal conductivity of ceramics and the relatively high electrical conductivity of carbon, along with the exceptional chemical resistance. The insights into the microstructure, atomic configuration, and property relationships of the resulting materials have broad implications for the development of multi‐phase nanostructured hybrid materials.