Visible-light Catalysed Trifluoromethylthiolation and Related Dearomative Spirocyclizations

We conceptualized a radical cyclization approach for the synthesis of SCF₃, SAr, SO₂Ar and COAr featured spirocyclic [4.5] and [5.5] trienone between biaryls and ArSO₂H or ArCOCO₂H in presence of RFTA as a photocatalyst whereas the insertion of ArSSAr or AgSCF₃ devoid of photocatalyst via an energetically demanding dearomative transformation under visible-light catalysis. The photo-excited charge transfer complex with biaryl tethered ynones provides a way to promote S-centered radical generation followed by its insertion to enable a wide range of biologically important molecules.     

Poly(3‐dodecyl thiophene)—Organically modified montmorillonite clay nanocomposites: Influence of chain regioregularity and preparation condition on physical,mechanical, optical,and conductivity properties

The properties of regioregular(R) (98.5 mol % H‐T) and regioirregular(I) (80.5 mol % H‐T) poly(3‐dodecyl thiophene)(P3DDT)—organically modified montmorillonite (om‐MMT) clay nanocomposites obtained from solvent‐cast and melt‐cooled procedures are compared. The solvent‐cast P3DDTI nanocomposites showed partially exfoliated clay structure but P3DDTR nanocomposites showed multistack exfoliation. Type 1 crystalline polymorph was produced in solvent‐cast systems whereas melt‐cooled P3DDTI samples showed mesomorphic structure. Storage modulus of P3DDTI nanocomposites increased with clay concentration showing a maximum increase of 255%. The UV‐vis spectra showed blue shift of π–π* transition band and photoluminescence spectra indicated seven times increase of normalized intensity in solvent cast P3DDTI composites. DC conductivity and I–V characteristic curves showed increased insulating properties with om‐clay concentration. The physical, mechanical, and optical properties of P3DDTI nanocomposites are more improved than that of P3DDTR nanocomposites and from their pristine polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Sorption and permeation of acetic acid–water mixtures by pervaporation using copolymer membrane

Poly (acrylonitrile‐co‐methyl acrylate) copolymer designated as PANMA was used for making pervaporation membrane. This membrane was used for separation of acetic acid–water mixtures over the concentration range of 80–99.5 wt% acetic acid in water. Interaction parameters based on Flory–Huggins lattice model and engaged species induced clustering (ENSIC) model was used to explain swelling of the membranes. Coupling in sorption was explained in terms of activity coefficient of water and acid in feed and membrane using Flory–Huggins model and also by interpolating ENSIC parameters. Flow coupling in pervaporation was also determined from phenomenological deviation coefficients. Intrinsic membrane properties like partial permeability and membrane selectivity of the solvents were also determined. Diffusion coefficient and plasticization coefficient of the solvents were obtained using a modified solution–diffusion model. The copolymer membrane showed high flux and water selectivity for highly concentrated acid. Thus, at 30°C temperature 1–20 wt% water in feed was concentrated to 82–84 wt% water in permeate and for 0.95 wt% water in feed, the membrane showed thickness normalized flux and water selectivity of 1.71 kg m^?2 h^?1 mμ and 409, respectively. OLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Polyacrylic acid (poly-A) as a chelant and dispersant

Polyacrylic acid was synthesized in water by persulfate-initiated polymerization (solution polymerization) of glacial acrylic acid in the absence of a chain-transfer agent. The final product is odorless and colorless. Chelation for calcium ions using a calcium electrode show that our poly(acrylic acid) has a higher chelation capacity than that of existing commercial poly(acrylic acids). A design of experiments was performed to optimize the synthesis conditions to obtain poly(acrylic acid) with a high maximum chelation value. These studies also helped us to gain insight into its high chelation capacity. The chelation capacity for calcium reaches its highest values when polymerization near isothermal conditions is done ∼ 95°C with an acrylic acid concentration of ≤21 wt % and an addition time >1 h. These conditions favor higher molecular weight poly(acrylic acid) with a polydispersity ∼ 4. The dispersion properties of our poly(acrylic acid) are similar to those of the commercial ones. This dual capability of chelation and dispersion is absent in commercial chelants such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and their analogs. At pH > 7, chelation of calcium by our poly(acrylic acid) is much higher than that observed with EDTA. Characterization by NMR, Raman, FTIR, and molecular modeling are included in an attempt to understand structural features that can explain the higher chelation capacity of our atactic poly(acrylic acid).     

INVESTIGATION OF A NOVEL MICROREACTOR FOR ENHANCING MIXING AND CONVERSION

A novel microreactor with a network of omega-shaped microchannels has been designed, fabricated, and tested for enhanced chemical species mixing and reaction conversion. Fluidic and mixing properties of the omega channel reactor have been investigated by means of computational fluid dynamic (CFD) simulation. Also, a stochastic model describing particle transport in the axial direction was applied to characterize the residence time distribution or the cumulative probability of a particle exiting the microreactor over time. Both fluidic simulation and stochastic model approaches revealed the advantage of the omega-shaped microchannels as compared to straight or zigzag-shaped microchannels. Fischer-Tropsch reactions were carried out using sol-gel encapsulated iron and cobalt catalysts in the omega-shaped microchannels. The experimental results showed that the conversion rate for the omega-shaped microchannels was considerably higher than that for the conventional straight microchannel or for the zigzag-shaped microchannels. These results were consistent with the fluidic simulation and the stochastic modeling results.     

Effect of layered silicate on EPDM/EVA blend nanocomposite: Dynamic mechanical,thermal, and swelling properties

Polymer blend nanocomposites have been developed by solution method using ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA‐45) copolymer, and organically modified layered silicate. Morphological investigation made by wide‐angle X‐ray diffraction and transmission electron microscopic analysis indicates intercalated structure of EPDM/EVA nanocomposites with partial disorder. Scanning electron microscopic studies exhibit the phase behavior of EPDM/EVA blend nanocomposites. Dynamic mechanical thermal analysis shows a significant increase in storage modulus in the rubbery plateau. The decrease in damping (tan δ) value and enhanced glass‐transition temperature (T_g) demonstrate the reinforcing effect of layered silicate in the EPDM/EVA blend matrix. The tensile modulus of these nanocomposites also showed a significant improvement with the filler content. The main chain scission of EPDM/EVA blend nanocomposites compared with the neat EPDM/EVA blend showed substantial improvement in thermal stability in nitrogen, whereas a sizeable increase is observed in air. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Interface engineering for the improvement of mechanical and thermal properties of covalent functionalized graphene/epoxy composites

Functionalized reduced graphene oxide (GO)/epoxy composites are fabricated through solution mixing. GO is functionalized using 3‐amino‐1,2,4‐triazole (TZ) in presence of potassium hydroxide (KOH). KOH is expected to serve dual role as catalyst for nucleophilic addition reaction between GO and TZ, and also as reducing agent. The grafting of TZ moiety on GO is confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis. The prepared composites show remarkable improvement in mechanical and thermal stability. The fracture toughness of the composites (critical stress intensity factor, K_IC) achieved from single edge notched bending testing is improved by ～111% against pure epoxy at 0.1 wt % loading of TZ functionalized GO. Further, the tensile strength and Young's modulus are improved by ～30.5% and 35%, respectively. Thermal stability of the composites as investigated by thermogravimetric analysis showed 29 °C rise in onset degradation temperature for 0.1 wt % TZ functionalized GO incorporated composite. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46124.     

Chemical functionalization of graphene and its applications

Functionalization and dispersion of graphene sheets are of crucial importance for their end applications. Chemical functionalization of graphene enables this material to be processed by solvent-assisted techniques, such as layer-by-layer assembly, spin-coating, and filtration. It also prevents the agglomeration of single layer graphene during reduction and maintains the inherent properties of graphene. Therefore, a detailed review on the advances of chemical functionalization of graphene is presented. Synthesis and characterization of graphene have also been reviewed in the current article. The functionalization of graphene can be performed by covalent and noncovalent modification techniques. In both cases, surface modification of graphene oxide followed by reduction has been carried out to obtain functionalized graphene. It has been found that both the covalent and noncovalent modification techniques are very effective in the preparation of processable graphene. However, the electrical conductivity of the functionalized graphene has been observed to decrease significantly compared to pure graphene. Moreover, the surface area of the functionalized graphene prepared by covalent and non-covalent techniques decreases significantly due to the destructive chemical oxidation of flake graphite followed by sonication, functionalization and chemical reduction. In order to overcome these problems, several studies have been reported on the preparation of functionalized graphene directly from graphite (one-step process). In all these cases, surface modification of graphene can prevent agglomeration and facilitates the formation of stable dispersions. Surface modified graphene can be used for the fabrication of polymer nanocomposites, super-capacitor devices, drug delivery system, solar cells, memory devices, transistor device, biosensor, etc.     

ECG signal classification and arrhythmia detection using ELM-RNN

Arrhythmia is a unique type of heart disease which produces inefficient and irregular heartbeat. This is a cardiac disease which is diagnosed through electrocardiogram (ECG) procedure. Several studies have been focused on the speed and accuracy on the learning algorithm by applying pattern recognition, artificial intelligence in the classification algorithm. In this work a novel classification algorithm is planned based on ELM (Extreme Learning Machine) with Recurrent Neural Network (RNN) by using morphological filtering. The popular publicly available ECG arrhythmia database (MIT-BIH arrhythmia DB) is used to express the performance of the proposed algorithm where the level of accuracy is compared with the existing similar types of work. The comparative study shows that performance of our proposed model is much faster than the models working with RBFN (radial basis function network), BPBB(back propagation neural network) and Support Vector Machine. The experimental result with the MIT BIH database with hidden neurons of ELM with RNN, the accuracy is 96.41%, sensitivity 93.62% and specificity 92.66%. The classification methodology follows main four steps the heart beat detection, the ECG feature extraction, feature selection and the construction of the proposed classifier.

     

Separation of toluene–methanol mixtures by pervaporation using crosslink IPN membranes

Polyvinyl alcohol (PVOH) has been chemically modified by crosslink copolymerization of acrylic acid (AA) and hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH to produce a full interpenetrating network (IPN) membrane termed as PVAH. Accordingly, three such full crosslink IPNs membranes, i.e. PVAHI, PVAHII and PVAHIII containing varied weight ratio of PVOH and copolymer have been synthesized and used for pervaporative separation of methanol from its mixtures with toluene. For comparison, a conventional PVOH membrane crosslinked with glutaraldehyde has also been used for the same pervaporation study. The flux and selectivity of these IPN membranes were found to be much higher than the conventional glutaraldehyde crosslinked PVOH membrane. Among the three membranes, PVAHII with 50 wt% polyAH incorporation showed optimum performance in terms of flux and methanol selectivity.