NIRAJ VISHWAKARMA - Academia.edu (original) (raw)

Papers by NIRAJ VISHWAKARMA

Chemical Engineering Journal, 2023

Journal of Applied Polymer Science, 2012

Novel amphiphilic ABA-type poly(D-gluconamidoethyl methacrylate)-b-polyurethane-b-poly(D-gluconam... more Novel amphiphilic ABA-type poly(D-gluconamidoethyl methacrylate)-b-polyurethane-b-poly(D-gluconamidoethyl methacrylate) (PGAMA-b-PU-b-PGAMA) tri-block copolymers were successfully synthesized via the combination of the step-growth and copper-catalyzed atom transfer radical polymerization (ATRP). Dihydroxy polyurethane (HO-PU-OH) was synthesized by the step-growth polymerization of hexamethylene diisocyanate with poly(tetramethylene glycol). PGAMA-b-PU-b-PGAMA block copolymers were synthesized via copper-catalyzed ATRP of GAMA in N, N-dimethyl formamide at 20°C in the presence of 2, 2′-bipyridyl using Br-PU-Br as macroinitiator and characterized by 1H-NMR spectroscopy and GPC. The resulting block copolymer forms spherical micelles in water as observed in TEM study, and also supported by 1H NMR spectroscopy and light scattering. Miceller size increases with increase in hydrophilic PGAMA chain length as revealed by DLS study. The critical micellar concentration values of the resulting block copolymers increased with the increase of the chain length of the PGAMA block. Thermal properties of these block copolymers were studied by thermo-gravimetric analysis, and differential scanning calorimetric study. Spherical Ag-nanoparticles were successfully synthesized using these block copolymers as stabilizer. The dimension of Ag nanoparticle was tailored by altering the chain length of the hydrophilic block of the copolymer. A mechanism has been proposed for the formation of stable and regulated Ag nanoparticle using various chain length of hydrophilic PGAMA block of the tri-block copolymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

International Journal of Biological Macromolecules

Journal of Macromolecular Science, Part A, 2020

Double hydrophilic ABA-type amphiphilic polyurethane (PU)-based poly(N-vinylpyrrolidone) (PNVP)-b... more Double hydrophilic ABA-type amphiphilic polyurethane (PU)-based poly(N-vinylpyrrolidone) (PNVP)-b-PUb -PNVP and poly(N-isopropylacrylamide) (PNIPAM)-b-PUb -PNIPAM triblock copolymers have successfully been synthesized via the combination of the step-growth polymerization, reversible addition-fragmentation chain transfer (RAFT) polymerization and azide-alkyne click reaction. All polymers are characterized by 1 H NMR, FTIR, and gel permeation chromatography.

ChemistrySelect, 2018

We have first synthesized acid-degradable alkyne-terminated aliphatic polyketal and thereof synth... more We have first synthesized acid-degradable alkyne-terminated aliphatic polyketal and thereof synthesized novel pH-responsive double hydrophilic amphiphilic block copolymer of poly(Nvinyl pyrrolidone) (PNVP) and aliphatic polyketal (PK) (PNVP-b-PK-b-PNVP via click chemistry upon reaction with azideterminated PNVP. Formation of block copolymer is confirmed by proton nuclear magnetic resonance, gel permeation chromatography, thermogravimetry, differential scanning calorimetry, and fluorescence spectroscopy techniques. pH-dependent degradation study of the block copolymer shows faster degradation at lower pH. Transmission electron micro-scopy (TEM) has revealed the formation of tiny (∼ 3.8 nm) micellar nanoparticles. Loading of the anticancer drugs doxorubicin (Dox) and imatinib in the micelle is confirmed from UV-Visible, and TEM studies. Drug release study from drug-loaded micelles has shown that imatinib is being released faster than Dox and both systems have shown higher load release at acidic pH of 6.4. Doxorubicin-and imatinib-loaded micelles demonstrate significant tumoricidal properties against parental and drug resistant human erythroleukemia K-562 and Dalton's lymphoma cells with respect to enhanced cellular uptake, cytotoxicity and growth inhibition.

Macromolecules, 2011

Well-defined amphiphilic poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) (PCL-b-PNVP) block copol... more Well-defined amphiphilic poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) (PCL-b-PNVP) block copolymers were successfully prepared via the combination of ring-opening polymerization (ROP) and xanthate-mediated reversible addition−fragmentation chain transfer (RAFT) ...

Langmuir, 2012

Poly(N-isopropylacrylamide) (PNIPAM) hydrogels and the corresponding linear homopolymers were syn... more Poly(N-isopropylacrylamide) (PNIPAM) hydrogels and the corresponding linear homopolymers were synthesized in different methanol-water mixtures (x(m) = 0, 0.13, 0.21, 0.31, 0.43, 0.57, and 0.76, where x(m) is the mole fraction of methanol) in the presence of 0.1 M Y(OTf)(3) Lewis acid. The isotacticity (meso dyad (m), %) and cloud-point temperature of these homopolymers were gradually increased and decreased, respectively, with the increase in the x(m) values of the synthesis solvent mixtures. Moreover, the corresponding linear PNIPAM homopolymers prepared in the absence of Y(OTf)(3) showed an almost constant isotacticity of m = 45% and a cloud-point temperature of 33.0 °C. A SEM study revealed that the resulting hydrogels were highly porous except for the gels prepared at x(m) = 0 and 0.76. The swelling ratios of these hydrogels in water at different temperatures and in different methanol-water mixtures at 20 °C and the deswelling rate and the reswelling rate of these hydrogels were studied. All of these swelling results were compared with that of the corresponding gels prepared in the absence of a Lewis acid (Biswas, C. S.; Patel, V. K.; Vishwakarma, N. K.; Mishra, A. K.; Bhimireddi, R.; Rai, R.; Ray, B. J. Appl. Polym. Sci.2012, DOI: 10.1002/app.36318) and explained on the basis of the porosity of the gel, the state of aggregation and isotacticity of the PNIPAM chain segment, and the cononsolvency of the methanol-water mixture toward the PNIPAM chain segment.

(S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and the newly syn-thesized (S)-2-(ethyl isobutyr... more (S)-2-(Ethyl propionate)-(O-ethyl xanthate) (X1) and the newly syn-thesized (S)-2-(ethyl isobutyrate)-(O-ethyl xanthate) (X2) were used as the revers-ible addition-fragmentation chain transfer (RAFT) agents for the radical polymerization of N-vinylpyrrolidone (NVP). The former showed the better chain transfer ability in the polymerization at 60 C. Kinetics study with X1 shows the psuedo-first order kinetics upto 45 % monomer conversion. Molecular weight (Mn) of the resulted polymer increases linearly with increase in the monomer conversion upto around 45%. Polydispersity of the corresponding poly(NVP)s increase grad-ually from 1.2 to 1.9 with increase in the monomer conversion. Chain-end analysis of the resulted polymer by 1H NMR shows clearly that polymerization started with radical forming out of xanthate mediator. Living nature of the polymerization was confirmed from the successful homo chain extension experiment and also the het-ero-chain extension experiment involving synthesi...

International Journal of Polymeric Materials and Polymeric Biomaterials, 2016

ABSTRACT Azide-terminated xanthate RAFT agent (S)-2-(4-azidobutyl propionate)-(O-ethyl xanthate) ... more ABSTRACT Azide-terminated xanthate RAFT agent (S)-2-(4-azidobutyl propionate)-(O-ethyl xanthate) has been synthesized and used for the controlled radical polymerization of N-vinylpyrrolidone (NVP). Kinetics study showed the pesudo first-order kinetics along with gradual increase in molecular weight (Mn) of the resulted polymer up to 69% conversion. Chain-end analysis of the resulted polymer by 1H NMR showed the presence of the fragments of xanthate mediator at both chain ends. Successful chain extension has also been performed via the click reaction of alkyne-terminated PNVP with azide-terminated PNVP. Moreover, fluorescence pyrene-tagged PNVP has successfully been made via the click reaction of alkyne-functionalized pyrene with azide-terminated PNVP. GRAPHICAL ABSTRACT

Journal of Biomaterials Science, Polymer Edition

ACS Applied Materials & Interfaces, 2022

RSC Advances, 2022

Correction for ‘Nanochannel conduction in piezoelectric polymeric membrane using swift heavy ions... more Correction for ‘Nanochannel conduction in piezoelectric polymeric membrane using swift heavy ions and nanoclay’ by Karun Kumar Jana et al., RSC Adv., 2013, 3, 6147–6159. DOI: 10.1039/C3RA23176C

New Journal of Chemistry, 2022

Solid supported catalysts such as amines are in high demand for the chemical fixation of CO2 into... more Solid supported catalysts such as amines are in high demand for the chemical fixation of CO2 into commodity chemicals.

Biomedical and Biotechnology Research Journal (BBRJ), 2021

Background: Nanoparticles modulate several physiochemical and biological properties. In this rega... more Background: Nanoparticles modulate several physiochemical and biological properties. In this regard, silver nanoparticles (AgNPs) have shown remarkable applications. The present research work comprises green synthesis of AgNPs using aqueous leaves extract of Eranthemum pulchellum and evaluation of its efficacy as antifungal and antioxidant agents. Methods: Synthesized AgNPs have been characterized by Fourier Transforms Infrared (FTIR) Spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and ultraviolet-visible spectrophotometry. Qualitative phytochemical analysis of aqueous leaves extract of E. pulchellum and FTIR spectrum of the synthesized AgNPs suggest about the presence of different phytochemicals and functional groups, respectively, which are responsible for reducing silver ions as well as capping and stabilizing synthesized nanoparticles. Results: The wavelength of maximum absorbance of AgNPs solution near to 439 nm indicates the spherical morphology. XRD infers about average crystalline size of the synthesized AgNPs to be ~12 nm. Selected area electron diffraction pattern of the synthesized AgNPs shows four visible diffraction rings corresponding to (111), (200), (220), and (311) set of planes which are attributed to face centered cubic metallic silver. The size and spherical shape of the synthesized AgNPs have been further determined by TEM. The synthesized AgNPs have shown a significant antifungal activity against Aspergillus flavus (AF-LHP-NS7) strain with minimum inhibitory concentration value of 200 μg/mL. The synthesized AgNPs have also shown strong antioxidant efficacy through Azino-bis-3-ethylbenzothiazoline-6-sulfonic acid assay with IC50 value of 462.56 μg/mL. Conclusions: The present study shows a green and facile synthesis of AgNPs. Leaves extract of E. pulchellum has been first time utilized as efficient reductant for the AgNPs synthesis. These AgNPs have shown potent antifungal and antioxidant activity.

Green Chemistry, 2020

Continuous-flow visible-light-induced decarboxylative annulation using a polydimethylsiloxane mic... more Continuous-flow visible-light-induced decarboxylative annulation using a polydimethylsiloxane microreactor containing immobilized Ru3+ has been established for the construction of fused imidazole derivatives.

Bulletin of the Korean Chemical Society, 2018

In the past decade, microreaction technology has been attracted much attention to the scientific ... more In the past decade, microreaction technology has been attracted much attention to the scientific community as one of the subareas in chemical synthesis. The microreactor improves the yield with higher selectivity, and also facilitates the reactions by simple, safe, fast, and green approaches. This review gives an overview on our contributions to develop versatile continuous-flow syntheses and process technology by exampling gas-liquid binary phase in modified PDMS microreactors, and process intensification for safe operation of toxic/hazardous chemistry by generating hazardous chemicals to end utilization via various separation techniques in newly devised systems as well as ordinary capillary reactors. Furthermore, it covers process technology for ultrafast organic synthesis such as submillisecond control of short-lived intermediates in a polyimide chip reactor. These works provide outlooks for integrated and automated flow chemistry via one-flow/feed to end concept, i.e., useful in pharmaceutical industry, toward enabling new and innovative chemistry beyond limits of a batch reactor.

Reaction Chemistry & Engineering, 2019

Accelerated Cu(0)-mediated homo-/block (co)polymerization of the vinyl monomers is conducted via ... more Accelerated Cu(0)-mediated homo-/block (co)polymerization of the vinyl monomers is conducted via continuous-flow process with a copper metal-wire catalyst threaded through perfluoroalkoxy alkane (PFA) tube.