Browsing by Author "Tarun Kumar Mandal"

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Synthesis and self-assembly properties of well-defined four-arm star poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) amphiphilic block copolymers
(2013) Avnish Kumar Mishra; K. Ramesh; Tapas Kumar Paira; Divesh N. Srivastava; Tarun Kumar Mandal; Nira Misra; Biswajit Ray
Well-defined amphiphilic four-arm star diblock copolymers of poly(ε-caprolactone) (PCL) and poly(N-vinylpyrrolidone) (PNVP) have successfully been synthesized by combining the ring-opening polymerization (ROP) of ε-caprolactone (CL) and xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization of N-vinylpyrrolidone (NVP). The resulting block copolymer shows the formation of spherical micelles in water as revealed by transmission electron microscopy (TEM) and supported by light-scattering study. The critical micellar concentration (cmc) value of the micelle increases with the increase in the PNVP block length. Hydrodynamic diameter distribution of the micelles decreases with the increase in the PNVP block length. The effective hydrodynamic ratio (R h) remains almost constant over the angles of scattering measurements above the corresponding cmc value. The usefulness of the synthesized star amphiphilic block copolymers was checked by the successful synthesis of silver nanoparticles. Graphical abstract: Well-defined four-arm star poly(ε-caprolactone)-b-poly(N-vinylpyrrolidone) amphiphilic block copolymers are prepared by the combination of ring opening polymerization and xanthate-mediated reversible addition-fragmentation chain transfer polymerization and their self-assembly properties are studied using 1H NMR, fluorescence spectroscopy, dynamic light scattering, and TEM. [Figure not available: see fulltext.] © 2013 Springer-Verlag Berlin Heidelberg.
Synthesis of well-defined amphiphilic poly(d,l-lactide)-b-poly(N- vinylpyrrolidone) block copolymers using ROP and xanthate-mediated RAFT polymerization
(Elsevier Ltd, 2012) K. Ramesh; Avnish Kumar Mishra; Vijay Kumar Patel; Niraj Kumar Vishwakarma; Chandra Sekhar Biswas; Tapas Kumar Paira; Tarun Kumar Mandal; Pralay Maiti; Nira Misra; Biswajit Ray
Well-defined amphiphilic poly(d,l-lactide)-b-poly(N-vinylpyrrolidone) (PDLLA-b-PNVP) block copolymers were successfully prepared using ring-opening polymerization (ROP) and xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization. Synthesized PDLLA-b-PNVP block copolymers were characterized by 1H NMR spectroscopy and GPC. Spherical micelles of ∼30.2 nm diameter were formed from the aqueous solution of amphiphilic diblock copolymer PDLLA42-b-PNVP63 as revealed by TEM and supported by 1H NMR and light scattering. The critical micelle concentration value of the block copolymers, determined by fluorescence spectroscopy using pyrene as probe, increased with the increase in the chain length of PNVP block. The average hydrodynamic radius (Rh) of the micelles remained almost constant above the cmc value over the angles of scattering measurement. Thermal properties of these block copolymers were studied by TGA, DTA and DSC. Crystalline properties of these block copolymers were studied by WXRD. © 2012 Elsevier Ltd. All rights reserved.
Synthesis of well-defined amphiphilic poly(ε-caprolactone)-b-poly(N- vinylpyrrolidone) block copolymers via the combination of ROP and xanthate-mediated RAFT polymerization
(2011) Avnish Kumar Mishra; Vijay Kumar Patel; Niraj Kumar Vishwakarma; Chandra Sekhar Biswas; Manoj Raula; Arvind Misra; Tarun Kumar Mandal; Biswajit Ray
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) polymerization. Well-defined poly(ε-caprolactone) (PCL-OH) was synthesized by ROP in bulk at 110 °C using benzyl alcohol as initiator and stannous octate [Sn(Oct)2] as catalyst. The -OH end group was then converted into its corresponding xanthate (PCL-X) via the conversion to its corresponding bromide (PCL-Br). These are verified by 1H NMR spectroscopy. PCL-b-PNVP block copolymers were synthesized via RAFT polymerization in tetrahydrofuran (THF) at 80 °C using PCL-X as macro-chain transfer agent and characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The amphiphilic diblock copolymer PCL63-b-PNVP90 forms spherical micelles of ∼34 nm diameter in water as shown by transmission electron microscopy (TEM), supported by 1H NMR spectroscopy, and light scattering. The critical micellar concentrations were determined by fluorescence spectroscopy using pyrene as probe. The critical micelle concentration (cmc) value of the block copolymers increases with the increase in the chain length of PNVP block. The overall hydrodynamic radius (Rh) of the micelles remains almost constant over the concentration range above the cmc value and over the angles of scattering measurement. © 2011 American Chemical Society.
Synthesis, characterization, and application of novel amphiphilic poly(D-gluconamidoethyl methacrylate)-b-polyurethane-b-poly(D-gluconamidoethyl methacrylate) triblock copolymers
(2013) Niraj Kumar Vishwakarma; Avnish Kumar Mishra; Abhinay Mishra; Tapas Paira; Vijay Kumar Patel; Chandra Sekhar Biswas; Tarun Kumar Mandal; Pralay Maiti; Biswajit Ray
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.
Synthesis, characterization, and solution behavior of well-defined double hydrophilic linear amphiphilic poly (N-isopropylacrylamide)-b-poly (ε-caprolactone)-b-poly (N-isopropylacrylamide) triblock copolymers
(Springer Verlag, 2014) Avnish Kumar Mishra; Niraj Kumar Vishwakarma; Vijay Kumar Patel; Chandra Sekhar Biswas; Tapas Kumar Paira; Tarun Kumar Mandal; Pralay Maiti; Biswajit Ray
Well-defined linear dihydrophilic amphiphilic ABA-type triblock copolymers of ε-caprolactone (CL) and N-isopropylacrylamide (NIPAAm) have successfully been synthesized with a high yield by combining the ring opening polymerization (ROP) and xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization methods. The resulted block copolymer shows the formation of micelles in water as supported by light scattering. The critical micelle concentration (cmc) value of the micelle increases with the increase in the chain length of the poly (N-isopropylacrylamide) (PNIPAAm) block. Cloud point of the block copolymers decreases with the decrease in the PNIPAAm chain length. The TGA analysis shows a one-step degradation and a lower thermal stability of the triblock copolymer than the PNIPAAm. The DSC analysis of the triblock copolymer shows the lowering of glass transition temperature (Tg), and melting temperature (Tm) peaks possibly due to the partial miscibility of the poly (ε-caprolactone) (PCL) block with the amorphous PNIPAAm block through the interaction of ester groups of PCL with the amide groups of PNIPAAm. The XRD pattern of the triblock copolymer shows a broad peak due to the suppression of the crystallization of PCL block owing to the mixing of PNIPAAm block with the PCL block. © 2014 Springer-Verlag.