Journal Articles
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Item A continuous flow microreactor as a practical tool for the synthesis of active pharmaceutical ingredients(Institution of Chemical Engineers, 2024) Bhaskar, K.; Rashed, M.; Bhat, K.; Lee, J.; Kim, K.-H.; Buruga, K.Continuous flow processing has become a key technology to maximize the capabilities of chemical syntheses. Numerous new tactics have been devised to synthesize various chemicals including active pharmaceutical ingredients (APIs) via a continuous flow system using microreactors. This review aims to illustrate the holistic system approach and diverse applications of continuous flow microreactors for the synthesis of APIs (with respect to type, design, and fabrication). This review also highlights the applicability of continuous flow microreactors in the synthesis of APIs in contrast to conventional batch-type methods along with a discussion of their merits and demerits. Overall, this review is expected to offer valuable insights into the utility of continuous flow microreactor technology for the upscaled production of commercially feasible APIs. © 2024 The Institution of Chemical EngineersItem Donor-acceptor polymers by solid state eutectic melt reaction for optoelectronic applications(Elsevier Ltd, 2017) Bathula, C.; Kang, Y.; Buruga, K.We report, the synthesis of novel donor–acceptor conjugated polymers based on benzo[1,2-b:4,5-b?]dithiophene (BDT) donor and 4,7-bis(5-bromothiophen-2-yl)benzo[c] [1,2,5]thiadiazole (DTBT) acceptor by solvent-free eutectic melt polymerization reaction (EMP). The most important fact is, reaction between solid reactants actually proceeds through bulk liquid phases, due to the formation of eutectics between the reactants and product(s) and any evolution of heat. In the present study, crystalline solid with moderately high vapor pressure and low melting temperature such as naphthalene is explored for forming eutectics in melt polymerization reaction. The HOMO and LUMO energy levels of the polymer P2 synthesized by EMP were found to be ?5.30 eV and ?3.77 eV. Optical bandgap was determined to be 1.53 eV. The solid-state reactions are important not only due to their high efficiency and selectivity but also for their more economical and eco-friendly procedures involved in the reaction. © 2017 Elsevier B.V.Item Optical, Electrochemical and Thermal Studies of Conjugated Polymers Synthesized by Eutectic Melt Reaction(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Bathula, C.; Buruga, K.; Kang, Y.; Khazi, I.A.M.This paper reports on the synthesis of a novel donor–acceptor conjugated polymers, P1 and P2 by solvent free eutectic melt polymerization reaction. Triisopropylsilylethynyl(TIPS) substituted benzo[1,2-b:4,5-b?]dithiophene(BDT) is used as donor, thienithiophene(TT) and thienopyrroledione(TPD) are utilized as acceptors for demonstrating eutectic polymerization. The most important fact in the solvent-free reaction between solid reactants actually proceeds through bulk liquid phases. Such liquid phases are possible due to the formation of eutectics between the reactants and product(s) and any evolution of heat. Naphthalene is explored in this reaction for forming eutectics with the reactants, resulting in desired polymers. Thermal stability, optical and electrochemical properties of these polymers were determined. Optical band gaps of the polymers were found to be 1.58 and 1.65 eV. Electrochemical studies by cyclic voltametry experiment revealed HOMO and LUMO energy levels to be ?5.22, ?5.60 eV, and ?3.76, ?4.16 eV, respectively. The polymers were thermally stable up to 285–400 °C. Thermal, optical and electrochemical studies indicated these materials to be promising candidates in organic electronic applications. © 2017, Springer Science+Business Media New York.Item Microwave assisted synthesis of bithiophene based donor-acceptor-donor oligomers and their optoelectronic performances(Elsevier B.V., 2017) Bathula, C.; Buruga, K.; Lee, S.K.; Khazi, I.A.M.; Kang, Y.In this article we present the synthesis of two novel bithiophene based symmetrical ? conjugated oligomers with donor-acceptor-donor (D-A-D) structures by microwave assisted PdCl2(dppf) catalyzed Suzuki coupling reaction. These molecules contain electron rich bithiophene as a donor, dithienothiadiazole[3,4-c]pyridine and phthalic anhydride units as acceptors. The shorter reaction time, excellent yields and easy product isolation are the advantages of this method. The photophysical prerequisites for electronic application such as strong and broad optical absorption, thermal stability, and compatible energy levels were determined for synthesized oligomers. Optical band gap for the oligomers is found to be 1.72–1.90 eV. The results demonstrated the novel oligomers to be promising candidates in organic optoelectronic applications. © 2017 Elsevier B.V.Item Green synthesis of palladium nanoparticles using fenugreek tea and their catalytic applications in organic reactions(Elsevier B.V., 2017) Mallikarjuna, K.; Bathula, C.; Buruga, K.; Shrestha, N.K.; Noh, Y.-Y.; Kim, H.In this communication, we present the fenugreek tea aided green synthesis of Pd nanoparticles (PdNPs@FT). The synthesized PdNPs were characterized by UV–Visible spectroscopy, scanning electron microscopy (SEM), small area electron diffraction (SAED), fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). FT-IR manifested that polyol and amide groups present in fenugreek may have participated in the synthesis of palladium nanoparticles. PdNPs@FT exhibited high catalytic activity towards hydrogenation of 4-nitrophenol to 4-aminophenol. PdNPs@FT catalyzed Suzuki–Miyaura coupling reaction between bromobenzene and phenyl boronic acid gave desired biphenyl in excellent yield. © 2017 Elsevier B.V.Item Selenophene based benzodithiophene polymers as potential candidates for optoelectronic applications(Elsevier Ltd, 2018) Bathula, C.; Khadtare, S.; Buruga, K.; Kadam, A.; Shrestha, N.K.; Noh, Y.-Y.This work reports on the synthesis and characterization of two novel conjugated polymers consisting of selenophene substituted benzo[1,2-b:4,5-b?]dithiophene (SeBDT) donor, and dithienothiadiazole[3,4-c]pyridine(DTPyT)-P1 or thieno[3,4]pyrroledione(TPD)-P2 acceptors. The synthesized polymers are characterized for the significant photophysical prerequisites essential for organic electronics such as strong and broad optical absorption, thermal stability, and compatible highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels. The polymers are thermally stable up to 280–370 °C, and the optical band gaps for P1, P2 calculated from their film absorption edges are found to be 1.53 and 1.84 eV, respectively. In addition, the electrochemical studies of P1, P2 reveal the HOMO and LUMO energy levels of ?5.02,-5.04 eV, and ?3.49, ?3.20 eV, respectively, suggesting these materials to be potential candidates for the applications in organic electronics. © 2017 Elsevier LtdItem A facile synthesis of halloysite nanotubes based polymer nanocomposites for glass coating application(Elsevier Ltd, 2018) Buruga, K.; Kalathi, J.T.Halloysite-based polymethyl methacrylate (HNT-PMMA) and polystyrene (HNT-PS) nanocomposite coatings for glasses were synthesized by ultrasound-assisted solution blending method. The coatings were then dip-coated on four different types of soda-lime glass and the spectral, mechanical properties of the coated glasses were analyzed. The coated glass samples displayed a better scratch resistance and surface hydrophobicity, compared to uncoated samples, without any significant changes in their inherent spectral properties. The thermal and mechanical properties (Tg and tensile strength) of the nanocomposites were also enhanced compared to neat polymers. The improvement in thermal and scratch resistance of the coatings is ascribed to the inclusion of halloysite nanotubes (HNTs) in the polymer matrix. Hence, HNT-based PMMA/PS nanocomposite coatings can be effectively used for glasses in automotive and architectural applications. © 2017 Elsevier B.V.Item Polystyrene-halloysite nano tube membranes for water purification(Korean Society of Industrial Engineering Chemistry A-803 Twin Bldg 275-3 Yangjae-Dong Seocho-Kul Seoul 137-130, 2018) Buruga, K.; Kalathi, J.T.; Kim, K.-H.; Ok, Y.S.; Boukhvalov, B.Membrane technologies are a sustainable solution for treatment of water and wastewater. Here, the technical feasibility of polystyrene-halloysite nanotube (PS-HNT) membranes, fabricated by an ultrasound-assisted solution casting method, was explored for water purification. To this end, the effects of various solvents on the structure, morphology, thermal, and mechanical properties of PS-HNT membranes were investigated. Introduction of HNTs (5 wt%) into the polystyrene matrix demonstrated excellent thermal and mechanical properties along with good water flux, rejection of unwanted components, recovery, and regeneration cycles. These membranes were overall useful enough to purify real wastewater collected from pulp and paper mill. © 2017 The Korean Society of Industrial and Engineering ChemistryItem Fabrication of ?-MPS-Modified HNT–PMMA Nanocomposites by Ultrasound-Assisted Miniemulsion Polymerization(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Buruga, K.; Kalathi, J.T.Halloysite nanotubes (HNTs) were modified with ?-methacryloxypropyltrimethoxysilane (?-MPS) to improve their interaction with the polymer, and the modified HNTs (MHNTs) were subsequently used for the synthesis of MHNT–polymethylmethacrylate (PMMA) nanocomposites by miniemulsion polymerization assisted by ultrasound. Reduced agglomeration of HNTs due to modification with ?-MPS was evident from scanning electron microscopy analysis. Modification of HNTs and exfoliation of MHNTs in the polymer nanocomposite were confirmed by the presence of their respective characteristic peaks in Fourier-transform infrared spectra and x-ray diffraction patterns. Transmission electron microscopic analysis showed that the surface of the MHNTs differed significantly from that of unmodified HNTs. MHNT–PMMA nanocomposite exhibited significantly higher glass-transition temperature (Tg) compared with neat PMMA or unmodified HNT–PMMA nanocomposite. Hence, such modification of HNTs along with miniemulsion polymerization assisted by ultrasound is a promising approach to achieve better dispersion of HNTs in the polymer and to obtain nanocomposites with enhanced properties. © 2018, The Minerals, Metals & Materials Society.Item Performance of halloysite nanotube/poly(styrene-co-methylmethacrylate) nanocomposite coatings for the protection of soda-lime glass(Elsevier Ltd, 2019) Buruga, K.; Kalathi, J.T.Polymer-based coatings for the protection of glass surfaces are used considerably in the construction and automotive industries. This research article focuses on the potential use of halloysite nanotubes (HNT)/Poly(Styrene-co-Methylmethacrylate) (PS-co-PMMA) nanocomposites as coatings for the protection of soda-lime glass. The effect of HNT content and coating thickness on the spectral properties of the glass, morphology, surface-wettability, and thermo-mechanical properties of the nanocomposite coatings were investigated and reported. The inherent spectral behavior of glass was not altered significantly by the coatings when the content of HNTs in coatings was ? 5 wt %. The coated glasses also exhibited a slight increase in the solar skin protection factor (SSPF), but notable improvement in the solar material protection factor (SMPF) when the HNT content was high in coatings. Thermogravimetric analysis (TGA) revealed that the HNT/PS-co-PMMA nanocomposite coatings possess excellent thermal stability compared to the neat copolymer. The surface wettability of coated glasses by water droplets decreased substantially due to coatings as evident from contact angle measurements. The HNT/PS-co-PMMA nanocomposites also displayed enhanced tensile strength and scratch resistance with increasing HNT content of coatings up to 5 wt%. Overall, the performance of the coated glass was enhanced by the coatings. © 2018 Elsevier B.V.