Oil Bath Research Articles

Ultrasound‐assisted formic acid–choline chloride deep eutectic solvent pretreatment of cotton straw to extracted lignin

AbstractDeep eutectic solvent (DES) is a new type of green solvent that can be used for the separation of lignocellulosic components. In this study, ultrasound‐assisted DES pretreatment was used to treat cotton straw, which could retain most of the cellulose in cotton straw and separate hemicellulose and lignin at the same time. Here, DESs with different molar ratios were prepared using choline chloride as hydrogen bond acceptor and formic acid as hydrogen bond donor. Simultaneously changing the ultrasonic frequency and DESs synergistic extraction of lignin. Results show that the ultrasonic power is 32 kHz (room temperature), ultrasound 30 min, oil bath heat 3 h under the best conditions can significantly extract lignin, and the yield of lignin is 87.7% and the purity reached 97.3%. The characteristic peaks of FT‐IR confirmed the extraction of lignin. The structural characteristics of 2D‐HSQC also confirmed the effective separation of lignin, and x‐ray diffraction (XRD) and scanning electron microscope (SEM) confirmed the effect of ultrasound‐assisted DES pretreatment on lignocellulose structure. In short, this study provides a feasible method for the separation of lignocellulose.

Kinetic studies on the radical ring‐opening polymerization of 2‐methylene‐1,3,6‐trioxocane

AbstractRadical ring‐opening polymerization (RROP) of cyclic ketene acetals allows for the synthesis of functional and biodegradable polyesters. To gain a better understanding of RROP, kinetic studies of this reaction method are thus essential but still rare. In here we conducted kinetic experiments on RROP of 2‐methylene‐1,3,6‐trioxocan (MTC) for the first time. In line with earlier findings, the kinetic behavior could be distributed into a chain growth, stationary and step growth behavior probably caused by dominating branching and recombination reactions impacting the polymerization with increasing conversion. The impact of reaction conditions, such as monomer concentration, reaction temperature and source of energy input (Oil bath, microwave, UV light) were varied systematically. All of these factors were studied towards their influence on polymerization rate constant, density of branches (DB), polymer dispersity and molar mass. While each of these factors were impacted by the reaction conditions, the DB was only depending on monomer conversion. Elution fractionation of PMTC samples with high conversion proved decreasing DB with increasing molar mass. Altogether, this study gives a holistic insight into the kinetics of MTC under various means of free RROP, paving the way for developing a more hydrophilic polyester with adjustable DB and molecular weight.

COPOLYMERIZATION OF UNSATURATED OLIGOESTERS MODIFIED WITH NITROGEN-CONTAINING COMPOUNDS WITH METHYL METHACRYLATE

In the present work, the kinetics of radical copolymerization in solution at the initial stages of polyglycol maleinate phthalates modified with nitrogen-containing compounds with methyl methacrylate in a ratio of 1:1 was studied. Cyclohexanone was used as a solvent, and benzoyl peroxide was used as an initiator. The study was carried out at temperatures of 50 and 60 °C by dilatometry using collapsible dilatometers and a centrifuge. 13 amine-containing compounds of different types were chosen as modifiers. Also, for comparison, the possibility of using amides and hydrazines as modifiers was checked. Polycondensation was carried out in an oil bath at 175 °C and with vigorous stirring with water withdrawal until a constant acid number was reached. It is shown that the addition of 0.1 mol/l modifier during the polycondensation of a mixture of maleic and phthalic anhydrides with ethylene glycol makes it possible to obtain an unsaturated oligoester, for which the temperature coefficient of the reaction of its copolymerization with methyl methacrylate is significantly reduced. This allows for non-isothermal curing to increase the volume of the copolymer block without the risk of overheating and destruction. Of the studied amines, para-aminoacetophenone turned out to be the most effective; its use as a modifier makes it possible to reduce the temperature coefficient of the reaction from 2.1 to 1.7. The rate of copolymerization at the initial stages for the studied modified systems decreases from 2 to 20 times. The results of the work allow us to propose a technology for the production of polymeric materials by molding them in blocks of much larger sizes than with the use of traditional unsaturated oligomers. Also, calculations were carried out according to a special technique and the maximum size of a copolymer block in the form of a cylinder was determined, in which the height is equal to the radius, which can be obtained by forming it in a non-isothermal mode in a thin layer form with convection air cooling and the maximum allowable temperature in the system is 90 °C. It is shown that the volume of such a block, when using some modified oligomers, increases significantly. Some physical and mechanical characteristics of the obtained copolymers with methyl methacrylate were determined, and it was shown that modification with nitrogen-containing compounds does not improve or worsen the studied characteristics.

Construction of novel NH2-MIL-125(Ti)@ZnIn2S4 Z-scheme heterojunction and its photocatalytic performance regulation

In this work, a series of ZnIn2S4 nanosheets encapsulated NH2-MIL-125(Ti) heterostructures (NM-125(Ti)@ZIS) have been rationally designed and established through a facile oil bath method. The photocatalytic Cr(VI) reduction and H2 evolution performance on NM-125(Ti)@ZIS were elaborately modulated by adjusting the mass ratio of two components, introducing S vacancy and loading cocatalysts. The experimental results demonstrate that the optimized NM-125(Ti)@ZIS heterostructure with mass ratio 3:1 of NM-125(Ti) to ZIS has an excellent Cr(VI) reduction performance in neutral solution, giving 98% reduction efficiency within 60 min. Moreover, the NM-125(Ti)@ZIS heterostructure, following the introduction of sulfur vacancies and the incorporation of Pt nanoclusters, demonstrates an optimal visible light (λ > 420 nm) hydrogen evolution rate of 4.708 mmol/g/h, which is 5.82 times greater than that of pristine ZIS. A thorough investigation of the microstructures and photoelectrochemical properties of the NM-125(Ti)@ZIS heterostructures reveals that the intimate contact interface, sulfur vacancy, and Pt nanocluster serve to effectively enhance charge separation efficiency, thereby improving the photocatalytic performance. Further analysis on the charges behavior at the interface verifies that a novel Z-scheme heterojunction has been constructed between ZnIn2S4 and NH2-MIL-125(Ti).

Generalized analytical model for evaluating the gear power losses transition changing from windage to churning behavior

Although splash lubrication is usually adopted in the intermediate or tail gearbox of helicopters at low or moderate speed, and it appears that the oil jet lubrication used in a high-speed main reducer of helicopters would be turned into the splash lubrication that only a small part of gears is immersed in the oil sump due to the lubricating oil deposition by the mismatch between the oil feed and return. The classic drag power losses model is either used for the churning behavior of common splash lubrication or the windage behavior of oil jet lubrication, and is no longer suitable for this transition phenomenon of these two behaviors coexist. In this paper, a theoretical analytical method by introducing the windage contribution factor and air-oil ratio evolution model is proposed to predict the associated power losses for one single spur gear rotating partially immersed in an oil bath. To verify the accuracy and correctness, the theoretical calculations are then compared with the existing experimental data from Quiban et al. [33]. Based on this method, a generalized analytical model to evaluate the gear drag power losses for the windage, churning phenomenon and their transition behavior are established.

Reductive amination of furfural and furfurylamine with methoxides and MIL-53-NH2(Al)-derived Ru catalyst

BackgroundDifurfurylamine (DiFAM)22DiFAM: difurfurylamine. is a valuable chemical used in pharmaceuticals or polymers, but an efficient synthesis is rarely reported. One such method involves the imination of furfural (FAL)33FAL: furfural. and furfurylamine (FAM)44FAM: furfurylamine. to form difurfurylimine (DiFIM),55DiFIM: difurfurylimine. followed by the hydrogenation of DiFIM to produce DiFAM. This process can be carried out effectively using Ru nanoparticles and borohydrides as catalyst and reducing agent, respectively. Understanding the mechanism of this reaction is crucial for designing similar systems in the future. MethodsThe materials Ru@Al2O3 and Ru/γ-Al2O3 were synthesized via in situ synthesis and impregnation, respectively. Characterization was then performed to verify the physicochemical properties of the materials. The catalytic reaction was carried out in an 80 °C oil bath with stirring for 1 h. Simulations were performed using density functional theory (DFT).66DFT: density functional theory. Significant findingsRu@Al2O3 obtained from MIL-53-NH2(Ru, Al) demonstrated a higher dispersion of Ru NPs due to their interaction with the –NH2 ligands on MIL-53-NH2(Al). Moreover, DFT calculations predicted that the methanolysis products of borohydrides could reduce the activation energy of the reaction by forming a stable transition state. These factors combined to yield an impressive ca. 92% of DiFAM and provide new insights for designing hydrogenation systems.

Growth and optical properties of ZnO nanorods on the full surface of porous silicon by sol–gel method and oil bath method

A method for the preparation of composites that allow the growth of ZnO nanorod structures on the full surface of porous silicon (polished surface, pore walls, and pore bottoms) is presented. The porous silicon is obtained by electrochemical etching of P-type silicon (100). The nanorods were grown in two steps: a sol–gel method and an oil bath method. The morphology of ZnO nanorods at different concentrations of the growth solution was investigated using scanning electron microscopy. X-ray diffraction confirmed the formation of ZnO hexagonal fibrous zincite structures. UV–Vis absorption spectroscopy confirmed that the composites possess good light absorption in the broad spectral region. In the wavelength range of 300 to 400 nm, the light absorption value of the porous silicon/zinc oxide (porous Si/ZnO) nanorods was increased by ~25% compared to that of the porous Si/ZnO films. The photoluminescence spectra confirmed the luminescence performance of the composites. Finally, the optical properties of the composites were further verified by simulation calculations.

Procedure to generate a selection chart for microwave sol-gel synthesis of nanoparticles

Numerical simulation is used to compare the temperature distribution existing during microwave or conventional heating by hot oil bath of a reaction volume. The simulation is applied to the sol-gel synthesis of TiO2 nanopowders, considering temperature dependent materials parameters. A WR340-based single mode applicator operating at 2.45 GHz is considered, with a cylindrical load positioned in regions of predominant electric field. A temperature homogeneity index, defined as the ratio between the average temperature and its standard deviation at a certain time, is used to compare homogeneity of conventional and microwave heating at different power densities, from 370 to 7400 W/L. Based on that comparison, a selection chart of the more homogenous heating process as a function of power density and average temperature of the reaction volume is defined and can be used to select the experimental conditions expected to lead to a more or less homogeneous particle size of the products.A dedicated instrumented model, including three optical fibres, is developed as well, for validation purposes. Experimental validation showed a very good predictive capability of the model, with errors on estimated temperature lower than 3 °C at temperatures lower than 80 °C.

Investigation of the Processes Occurring During the Operation of the Torque Converter Hub in the Belarusian Autoworks Gearbox during CAE Modeling

The main objective of the study is to identify and eliminate the causes of breakdowns in the torque converter hubs of mining dump trucks Belarusian Autoworks. The relevance of the work carried out: during the operation of dump trucks based on Belarusian Autoworks vehicles, in open pit conditions, according to enterprises operating such equipment, in the period from 2019 to 2021, 75% of the failures and breakdowns of equipment occurred due to the fact that the hub of the torque converter impeller is intensively loaded a part, which during its operation is affected not only by mechanical loads, but also by temperature and others leading to the failure of the specified unit in 85% of cases. For example, hydrodynamic forces that arise during the period of immersion of gear teeth in an oil bath, and so on. Therefore, it is proposed to conduct a comprehensive study of the processes occurring with the wheel hub and identify the main loaded places. Taking into account the analysis carried out, it is possible to produce a batch of wheel hubs with updated parameters and conduct their full-scale tests. The novelty of the work carried out lies in the analysis of the operating conditions of the hub, which revealed a high boundary pressure that occurs at the point of transition from the air to the oil bath. The object of research is the study of the processes that occur during the operation of the torque converter hub, which affect the structure and occur in the hub itself. Research objectives: - learn the ways and methods of conducting CAE analysis; - analyze the design parameters of the installation that occur in the torque converter bushing. Research methods: When performing the dissertation work, methods of physical and mathematical modeling and system analysis of information, laboratory, bench and operational tests using computer and high-precision measuring equipment were used

The oil bath thermal cycling absorption process design and separation process research

Thermal cycling absorption process (TCAP) has been developed for years to support the separation of hydrogen isotopes, which has the characteristics of high separation efficiency and high recovery rate. The design of separation column structure, heating and cooling (H&C) system and technological parameters are the basis of TCAP technical process study and are the key points of TCAP engineering research. In this work, an improved separation system has been designed and built based on an oil bath H&C system for the first time. The separation column in this facility is 45 m long and the packing weight in the column is up to 8 kg. The separation experiments were carried out based on this facility, and the process parameters were adjusted according to the size of the separation column, which proved the superior performance of this facility. The separation experiments show that for 50% D2 - 50% H2 feed gas, the deuterium abundance can reach to 99% and the steady state extraction can be realized in production mode with the processing capacity over 400 standard L per day. Another experiment has been carried out with 1% D2 - 99% H2 feed gas, and the deuterium abundance exceeded 10%, verifying the separation ability at low abundance deuterium feed gas. Furthermore, the extraction rate can reach to 25% column capacity when the deuterium abundance in production gas is 5%.

Ultrathin PdCu Nanosheet as Bifunctional Electrocatalysts for Formate Oxidation Reaction and Oxygen Reduction Reaction.

The development of robust nonplatinum electrocatalysts to enhance the performance of formate oxidation reaction (FOR) and oxygen reduction reaction (ORR) is one of the key issues for the commercialization of direct formate fuel cells (DFFCs), but still challenging. Herein, a structurally controlled 3D flower-like PdCu nanosheet (NS) catalyst is synthesized by a method of oil bath reduction under mild conditions as a bifunctional electrocatalyst for DFFCs. Under the dual tuning on the composition and intermetallic phase, the PdCu nanosheet catalyst exhibits 8.67 times higher mass activity for anodic formate oxidation reaction than the commercial Pd/C. For the cathodic ORR, a positive shift half-wave potential is obtained for PdCu nanosheets exceeding Pt/C. Moreover, after a long-term stability test, the current density of the PdCu nanosheet catalyst for FOR and ORR can be well maintained with the least activity decay. When the PdCu NSs are used as optimized anode and cathode electrodes for DFFCs enable a peak power density as high as 53 mW cm-2 at room temperature, which is about 1.3 times higher than that of the commercial Pd/C and Pt/C as anode and cathode electrodes. This work provides a potential strategy to improve the catalytic performance of non-Pt-based nanocatalysts.

Phase transformation and physical properties of binding materials fabricated from solid waste FGD gypsum by oil bath heating and the micromorphology and formation mechanism of their hydration products

This work provides a novel approach to fabricate binding materials from flue gas desulfurization (FGD) gypsum. Results show that high performance binding materials composed of 96% hemihydrate gypsum (HH) and 4% anhydrite are prepared by calcining FGD gypsum at 190 ℃ for 90 min. They present low setting times and high mechanical strength, because HH promotes the saturation of [SO4]2- and Ca2+ ions in solution, leading to increases in their hydration activity and arrangement tightness of hydration product. Moreover, their hydration product dihydrate gypsum displays a stick-like structure with smooth surface and grows along [001] orientation by screw dislocation mechanism.

Development of an analytical model to predict the churning power losses of an orthogonal face gear

As one of the basic energy dissipations for one orthogonal face gear running partially submerged in an oil bath, there is no open literature concerned on the churning power losses of the face gear. This paper proposed a series of formulas to predict the churning losses for one orthogonal face gear running partially submerged in an oil bath. The analytical model of churning drag forces is based on fluid mechanics and boundary layer theory which enables quantitatively calculating the influences of the rotating speed, fluid attributes, and gear geometric construction with the minimum effort. Then, an ad hoc test bench was set up to carry out the specific splash lubrication tests for single face gear at different rotating speeds and initial immersion depth. Finally, considering both the churning and windage effects, a physical-based model adopting the real-time immersion depth instead of the static immersion depth is developed to calculate the total load-independent losses of a splash lubricated face gear. From this, the theoretical results are compared well with sets of directly measured experimental findings. Meanwhile, the model is also exploited to quantitate the contributions of each part in the total load-independent losses for one face gear under splash lubrication condition.

Green and Low-temperature Synthesis of Carbon Dots for Simple Detection of Kaempferol.

As a common flavonols, kaempferol (Kae) has a broad market as health food and medicine for its anti-inflammatory, anti-oxidation, and anti-cancer properties. In this study, a novel convenient and simple fluorescent sensor based on carbon dots (CDs) for the detection of Kae was developed. The fluorescent CDs, with excellent photo-luminescence (PL) and up-conversion luminescence (UCPL) properties, were successfully prepared by low-temperature oil bath reaction based on ascorbic acid as carbon source at 90°C in one pot. Under the optimal conditions, the fluorescence (FL) intensity of CDs was gradually quenched by the increasing addition of Kae with a linear relationship between F0/F and Kae concentration in a wide range from 5 µM to 100 µM with a detection limit of 0.38 µM. And this designed sensor was favourably applied for the detection of Kae in actual sample (xin-da-kang tablets). Moreover, the proposed CDs has great application prospects as a drug-sensor for detecting Kae due to its simple operation, economical and green materials, low equipment requirement, and rapid detection.

Time-Dependent Austempering of High Carbon Steel using Epoxidized Cotton Seed Oil

The work seeks to ascertain the potential of austempering time on the microstructure and mechanical properties of high carbon steel using epoxidized cotton seed oil bath. Five sets of high carbon steel (HCS) samples were heated to an austenitizing temperature of 830°C in the furnace, soaked at that temperature for 1 hour and quenched interruptedly at a temperature of 310°C in epoxidized cotton seed oil (ECO) bath for 15 – 75 minutes (at regular intervals of 15 minutes for different samples’ sets). Subsequently, samples air-cooled at ambient temperature. Hounsfield tensometer, Indentec universal hardness tester and Izod impact tester were used to determine the mechanical properties of the austempered samples. From the outcome of the investigation, appreciable improvement was noted in tensile strength (1210 N/mm2), hardness (397 HBN) and impact strength (12.1 J/mm) of the austempered samples. Further, samples were subjected to metallographic sample preparation, succeeded by microstructural examination using scanning electron microscope (SEM). The structures observed to be majorly bainite. The austempering time of 15 minutes produced the outstanding combination of mechanical properties.

Construction of highly dispersed NH2-MIL-101(Fe)/g-C3N4 heterostructure with excellent photocatalytic redox capability

Through a facile oil bath method, a novel highly dispersed NH2-MIL-101(Fe)/carboxylated g-C3N4 (NM-101(Fe)/CCN) heterostructure was prepared using the chemical bonding between carboxyl groups and -NH2 groups. Compared with the octahedral morphology of pure NM-101(Fe), the chemical bonding interaction promoted the heterogeneous nucleation and growth of NM-101(Fe) to form nanometer-sized granular morphology, which was homogeneously dispersed on CCN surface. Cr(Ⅵ) and ciprofloxacin (CIP) were selected as the typical pollutant models in micro-polluted water sources. The results showed that 10 %NM-101(Fe)/CCN heterostructure could remove 97 % of Cr(Ⅵ) in 60 min and 88 % of ciprofloxacin (CIP) in 120 min. In the dual pollutant system of Cr(Ⅵ) and CIP, Cr(Ⅵ) reduction and CIP degradation can promote each other, and the degradation efficiency of CIP reached 96 % within 120 min. The apparent rate constant of 10 %NM-101(Fe) /CCN heterostructure for Cr(Ⅵ) reduction was 4.30 and 9.67 times of that of NM-101(Fe) and CCN, respectively, which may be ascribed to the interface electric field and good interface bonding of heterojunction. The charges separation efficiency was significantly improved, which effectively enhanced the photocatalytic activity.

New protocol for functionalization of fullerene soot with dinitrobenzene groups from a non-diazonium resource

The nitrobenzene functionalized fullerene soot has been considered as a potentially energetic material. In our previous study, the in situ produced nitrobenzene diazonium ions have been used for the synthesis of 2-nitrobenzene, 4-nitrobenzene and 2,4-dinitrobenzene functionalized fullerene soot nanoparticles with moderate oxygen (14.91 wt%) and nitrogen (6.27 wt%) contents. In the present study, a new protocol for the functionalization of fullerene soot with 3,5-dinitrobenzene groups from a non-diazonium resource is reported. The functionalization of fullerene soot is performed through Ag(I)-catalyzed decarboxylative oxidation of 3,5-dinitrobenzoic acid (DNBA) under conventional heating or microwave irradiation. The effects of various parameters such as the oil bath temperature and the amounts of substrate (DNBA), catalyst (AgNO3) and oxidant (K2S2O8) on these reactions are evaluated. The synthesized compounds are characterized by FT-IR, Raman, XRD, SEM-EDX and elemental mapping analysis, FE-SEM and TEM along with particle size analysis, as well as TGA-DSC. The DSC thermograms of functionalized fullerene soot show a single exothermic peak attributed to the exothermic decomposition of 3,5-dinitrobenzene groups. Some of these compounds have up to 82.16 wt% oxygen and 6.10 wt% nitrogen contents. These findings are important for development of the energetic materials with improved oxygen content.

Benzeneseleninic Acid Promoting the Selenofunctionalization of 2- Naphthol Derivatives: Synthesis and Antioxidant Activity of 1- Organoselanyl-naphthalen-2-ols

Background: We report the synthesis and antioxidant evaluation of 1-organoselanyl-naphthalen-2-ols. The title compounds were selectively prepared through the selenofunctionalization of 2-naphthol derivatives using benzeneseleninic acids as a selenium source. Objective: We aimed at synthesizing 1-organoselanyl-naphthalen-2-ol by functionalizing 2-naphthol with arylseleninic acids using glycerol as the solvent and further evaluating the pharmacological activity. Methods: The products were synthesized at 70 °C using glycerol as a solvent in an oil bath. Reactive species (RS) tests, DPPH radical scavenging activity assay, and ABTS+ radical scavenging activity assay were performed. A statistical analysis of the data was performed. Results and Discussion: A total of fifteen 1-organoselanyl-naphthalen-2-ols were selectively obtained in yields of 58-95% in 0.25-48 h of reaction. Additionally, all the synthesized seleno-derivatives exhibited antioxidant activity, as revealed by their ability to scavenge DPPH and ABTS+ radicals and reduce the reactive species (RS) levels. Conclusion: The synthesis of 1-arylselanyl-naphthalen-2-ols was developed under mild reaction conditions using benzeneseleninic acid derivatives in reactions with 2-naphthol. All synthesized 2-naphthol derivatives exhibited antioxidant activity, as revealed by their DPPH and ABTS+ radical scavenging activity and reduced RS levels.

The Effect of Adding V and Nb Microalloy Elements on the Bake Hardening Properties of ULC Steel before and after Annealing

Bake hardening (BH) is a vital part of special steel production. Studies in this field have focused on steels under homogeneous yielding, but until now, none have been conducted on the phenomena that occur for steels under heterogeneous yielding. In the current study, the effect of adding Nb and V alloying elements on the strength of ultra-low carbon (ULC) steel after bake hardening was investigated. The effects of pre-strain, grain size, and recrystallization annealing temperature were analyzed, as well as the effect of Nb and V on the yield stress caused by the bake hardening process. For this purpose, five types of alloys with different V and Nb contents were melted, cast in an induction furnace, and subjected to hot hammering and hot rolling. Then, cold rolling was applied to the samples by ~80%. To eliminate the effects of cold working, tensile samples were subjected to recrystallization annealing at 750 and 800 °C for 30 min, and the samples were quickly quenched in a mixture of a NaCl solution and ice. The annealed samples were subjected to a pre-tensile strain in the range of 2-12% and then aged in a silicone oil bath at 180 °C for 30 min. Then they were subjected to a tensile test. The obtained results showed that with the increase of the pre-strain and the annealing temperature, the values of baking hardness increased. The presence of V in the composition of steel reduced the annealing temperature.

Preparation and Characterization of a Novel Hyperbranched Polyester Polymers Using A2+B3 Monomers

Abstract Compared to linear analogs, hyperbranched polymers (HBPs) have gotten much attention in the last decade because of their intrinsic globular topologies and distinctive features like low viscosity, high solubility, and a high degree of functionality. In this work, four types of hyperbranched polyester polymer HBPs have been synthesized using the A2+B3 polycondensation methodology. Firstly, the starting material B3 monomer (Pyrimidine-2,4,6-triol) has been synthesized using urea and malonic acid with the presence of sodium Na as the catalyst for the reaction. Secondly, four types of materials (tartaric acid TA, adipic acid AD, maleic acid MA, and phthalic anhydride PA) as A2 monomers were added to the starting material B3 monomer in an oil bath to prepare the four types of HBP. The chemical structure of HBPs was characterized by FTIR, and 1H-NMR. The molecular weight of the prepared HBPs was characterized by gel permeation chromatography GPC, and thermal properties were characterized by differential scanning calorimetry DSC and thermal gravimetric analysis TGA. FTIR results showed that there are new bands, such as C-O-C between A2 and B3 monomers, as indicated by 1H-NMR. In addition, GPC shows that the prepared polymers have a narrow molecular weight distribution with good thermal stability, as indicated by DSC and TGA.