ATANU KUILA - Academia.edu (original) (raw)

Papers by ATANU KUILA

Research paper thumbnail of Supramolecular grafting of doped polyaniline leads to an unprecedented solubility enhancement, radical cation stabilization, and morphology transformation

Journal of Materials Chemistry A, 2018

Polyaniline supramolecularly grafted with polyethylene glycol coupled with β-cyclodextrin forming... more Polyaniline supramolecularly grafted with polyethylene glycol coupled with β-cyclodextrin forming a pseudorotaxane structure shows an extremely high solubility, higher degree of doping, and highly efficient radical cation stabilization.

Research paper thumbnail of Multi-functional poly(vinylidene fluoride) graft copolymers

Journal of Polymer Science Part A: Polymer Chemistry, 2017

Poly(vinylidene fluoride) (PVDF) is known for its biocompatibility, piezo and pyro-electricity, a... more Poly(vinylidene fluoride) (PVDF) is known for its biocompatibility, piezo and pyro-electricity, and membrane forming capability. In order to tune its properties, modification through grafting from approach by atom transfer radical polymerization (ATRP) is preferred. Hydrophilic polymers like poly(ethylene glycol) methacrylate, poly(methacrylic acid), poly(dimethylaminoethyl methacrylate) (PDMAEMA), and so forth have been anchored from PVDF backbone in order to make permeation of water molecules through the PVDF based membranes. The successful solution grafting of PDMAEMA chains from PVDF backbone by ATRP resulted appreciable graft conversion and hence its bulk properties showed a significant change. This water soluble graft copolymer shows incredible mechanical and adhesive properties. PVDF-g-poly(n-butyl methacrylate) generates honeycomb porous film using "breath figure" technique. Recently, they have used further improvement of grafting where model ATRP initiators are anchored using atom transfer radical coupling and used them as macroinitiators for grafting. This approach simplified the grafting reactions even more and enabled successful grafting of a large number of monomers under relatively less drastic conditions with appreciable conversion compared with the previous conditions. This technique has resulted interesting solution properties, ion and electron conducting PVDF, antifouling membrane, super glue and super tough materials, capable of generating metal nanoparticles tunable with pH and temperature. V

Research paper thumbnail of pH and temperature responsiveness in AgNPs stabilized by a new poly(vinylidene fluoride) random graft copolymer

Journal of Polymer Science Part A: Polymer Chemistry, 2017

Poly(vinylidene fluoride)(PVDF)-graft-random copolymers(PD) of diethyleneglycol methylether metha... more Poly(vinylidene fluoride)(PVDF)-graft-random copolymers(PD) of diethyleneglycol methylether methacrylate(MeO 2 MA) and dimethylaminoethyl methacrylate(DMAEMA) are synthesized by a combined atom transfer radical coupling and atom transfer radical polymerization technique at three different co-monomer compositions. The molar ratio of MeO 2 MA to DMAEMA in PD are measured to be 1:5.8, 1:1.3, and 1:0.5 for PD1, PD2, and PD3 graft copolymers. In PD2 the feed ratio and mole ratio are same indicating an azeotropic composition causing highest yield (89%) and highest molecular weight (9.29 3 10 5). The grafted chains of PD are temperature and pH responsive and in basic pH they show a sudden increase in size above certain temperature for LCST-type phase transition, however, this is not observed at pH 4 and 7. PD can generate AgNPs under UV irradiation and morphology of PD at 30 8C varies with pH from vesicle to nanosphere. The AgNPs lie on the surface of the vesicles or assemble with the PD chains forming nanosphere morphology. At different pH, PD samples exhibit plasmon peaks at different wavelengths attributed to various size, shapes and cluster formation. The UV-vis spectra of AgNPs stabilized by PD1 and PD2 samples exhibits similar LCST-type phase transition as observed above, but that of PD3 does not show any such transition. V

Research paper thumbnail of Deciphering the Effect of Polymer-Assisted Doping on the Optoelectronic Properties of Block Copolymer-Anchored Graphene Oxide

Research paper thumbnail of An insight into the schizophrenic self-assembly of thermo and proton sensitive graphene oxide grafted block copolymer

Journal of Polymer Science Part A: Polymer Chemistry, 2016

In order to study the self-assembly of block copolymer grafted from graphene oxide (GO) by the fl... more In order to study the self-assembly of block copolymer grafted from graphene oxide (GO) by the fluorescence of GO, poly(e-caprolactone) (PCL)-block-poly(dimethyl aminoethyl methacrylate) (PDMAEMA) is grafted from its surface using consecutive ring opening (ROP) and atom transfer radical polymerization (ATRP). GO-g-(PCL 13-b-PDMAEMA 117) (GPCLD) at pH 9.2 exhibits cloud point (T c) at 32 8C. At pH 9.2 HRTEM images indicate schizophrenic morphology from vesicle at 26 8C to annular ring at 30 8C followed by giant size aggregation at 38 8C. But the reference block copolymer (PCL 14-b-PDMAEMA 126 , PCLD), synthesized using benzyl alcohol as ROP initiator, exhibits only core-shell morphology whose size increases with rising temperature at pH 9.2. GPCLD solution exhibits good photoluminescence (PL) property arising from GO at pH 9.2 and PL-intensity increases abruptly during phase transition. Both T c and size of GPCLD assembly can be reversibly tuned by CO 2 and N 2 gas purging. 1 H NMR spectra exhibit a gradual shift of resonance peaks of the protons on CO 2 bubbling. Thus at pH 9.2 and at 38 8C the GPCLD acts as a good CO 2 sensor. Additionally, the GPCLD vesicle can load hydrophobic guest molecules which can be released by triggering with CO 2. V

Research paper thumbnail of Optoelectronic and photovoltaic properties of graphene quantum dot–polyaniline nanostructures

Journal of Materials Chemistry A, 2015

In aqueous dispersions of graphene quantum dots (GQDs), aniline is in situ polymerized to produce... more In aqueous dispersions of graphene quantum dots (GQDs), aniline is in situ polymerized to produce polyaniline-GQDs hybrids and dye-sensitized solar cells fabricated with the hybrids indicate highest power conversion efficiency of 3.12%.

Research paper thumbnail of Temperature triggered antifouling properties of poly(vinylidene fluoride) graft copolymers with tunable hydrophilicity

Journal of Materials Chemistry A, 2015

PVDF-g-PMeO2MA produced by combined ATRC and ATRP methods exhibits a tuneable LCST with graft com... more PVDF-g-PMeO2MA produced by combined ATRC and ATRP methods exhibits a tuneable LCST with graft composition and a temperature triggered antifouling property.

Research paper thumbnail of Amphiphilic poly(N-vinyl pyrrolidone) grafted graphene by reversible addition and fragmentation polymerization and the reinforcement of poly(vinyl acetate) films

Journal of Materials Chemistry A, 2013

ABSTRACT The reversible addition and fragmentation (RAFT) polymerization of vinyl pyrrolidone (VP... more ABSTRACT The reversible addition and fragmentation (RAFT) polymerization of vinyl pyrrolidone (VP) from graphene oxide (GO) is used to produce GO-g-PVP (GP) and the grafting is confirmed from Fourier transformed infrared (FTIR) and nuclear magnetic resonance spectra. The average thickness of GP (8.2 nm) obtained from atomic force microscopy is higher than that of GO (1.2 nm), indicating the wrapping of grafted PVP on the GO sheets. Transmission electron microscopy of GP exhibits swollen domains (white spots) characterizing the grafted PVP chains from the GO surface. The dispersibility of the GP sheets becomes greatly improved over that of GO and they are dispersible in the solvents of Hansen solubility parameter (δp + δH) range 6.3–58. Three nanocomposites GP1, GP3 and GP5, produced by mixing with 1, 3 and 5 (w/w)% GP with poly(vinyl acetate) (PVAc), produce a stable dispersion in dimethyl formamide, although mixtures of GO and PVAc do not. The field emission scanning electron microscopy of the GP5 sample indicates a good homogeneous dispersion of GP sheets within the PVAc matrix, although both GO and PVP are individually immiscible with PVAc. The FTIR data indicates a specific interaction between GP and PVAc. The glass transition temperature (Tg) of the pure PVAc increases in the GP composites, but in the GO composite it remains unchanged. In the GPP5 hybrid containing the GO, PVP and PVAc mixture produced at the same composition as in GP5, an increase of Tg is seen to a lesser degree than that of GP, indicating that GO acts as a compatibilizer of a PVP and PVAc immiscible blend. The mechanical properties of PVAc exhibit a strong reinforcement and the Young's modulus & tensile strength data show a 190% and 169% increase over PVAc in the GP5 sample due to the homogenous dispersion and unidirectional (parallel) orientation of GP sheets in the composite film.

Research paper thumbnail of On the pH sensitive optoelectronic properties of amphiphilic reduced graphene oxide via grafting of poly(dimethylaminoethyl methacrylate): a signature of p- and n-type doping

J. Mater. Chem. A, 2014

ABSTRACT Poly(N,N′-dimethylaminoethyl methacraylate) (PDMAEMA) functionalized reduced graphene ox... more ABSTRACT Poly(N,N′-dimethylaminoethyl methacraylate) (PDMAEMA) functionalized reduced graphene oxide (rGO) is synthesized by atom transfer radical polymerization, followed by attachment to rGO via diazonium coupling. The rGO-PDMAEMA (RGP) is characterized by 1H NMR, UV-Vis, FTIR and Raman spectroscopy. TEM and AFM studies demonstrate the formation of molecular brushes of PDMAEMA chains over rGO surface, and the TGA thermograms indicate 55 wt% grafting of PDMAEMA. RGP is dispersible in the widest spectrum of solvents from CCl4 to water [solubility parameter (δp + δh), 0.6 to 58]. RGP exhibits strongly pH dependent fluorescence properties: at pH 4, it exhibits two emission peaks, but at pH 7 and pH 9.2, a single and broad emission peak is observed. Two emission peaks at pH 4 are attributed to radiative decay of excitons to two kinds of holes in the rGO originating from illumination and p-type doping, which is also characterized by a blue shift of the Raman D band. Moreover, n-type doping of RGP at pH 9.2 is also evident due to a similar Raman shift. The dc-conductivity of RGP at pH 4 is 2 orders higher than that of pH 9.2 and the I–V characteristic curve at pH 7 exhibits a bimodal NDR property with a rectification ratio of 5.5. The bimodal NDR property is explained with a model using density of states and polaronic band.

Research paper thumbnail of Coupled atom transfer radical coupling and atom transfer radical polymerization approach for controlled grafting from poly(vinylidene fluoride) backbone

Journal of Polymer Science Part A: Polymer Chemistry, 2013

A new "grafting from" strategy for grafting of different monomers (methacrylates, acrylates, and ... more A new "grafting from" strategy for grafting of different monomers (methacrylates, acrylates, and acrylamide) on poly(vinylidene fluoride) (PVDF) backbone is designed using atom transfer radical coupling (ATRC) and atom transfer radical polymerization (ATRP). 4-Hydroxy TEMPO moieties are anchored on PVDF backbone by ATRC followed by attachment of ATRP initiating sites chosen according to the reactivity of different monomers. High graft conversion is achieved and grafting of poly(methyl methacrylate) (PMMA) exhibits high degree of polymerization (DPn 5 770) with a very low graft density (0.18 per hundred VDF units) which has been increased to 0.44 by regenerating the active catalyst with the addition of Cu(0). A significant impact on thermal and stress-strain property of graft copolymers on the graft density and graft length is noted. Higher tensile strain and toughness are observed for PVDF-g-PMMA produced from model initiator but graft copolymer from pure PVDF exhibits higher tensile strength and Young's modulus. V

Research paper thumbnail of Highly Fluorescent Graphene Oxide-Poly(vinyl alcohol) Hybrid: An Effective Material for Specific Au3+ Ion Sensors

ACS Applied Materials & Interfaces, 2012

We have developed a new highly fluorescent graphene oxide (GO)/poly(vinyl alcohol) (PVA) hybrid (... more We have developed a new highly fluorescent graphene oxide (GO)/poly(vinyl alcohol) (PVA) hybrid (GO-PVA) in an acidic medium (pH 4). Fourier transform infrared (FTIR) spectra indicate the formation of hydrogen bonds between the hydroxy group of PVA and the hydroxy groups of GO. The hybrid is highly fluorescent, because of passivation by hydrogen bonding, as evident from Raman spectra. The quantum yields of GO-PVA hybrids are higher than that of GO. The fluorescent microscopic images of the hybrids exhibit a fibrillar morphology, and all of them emit highly intense green light. Field-emission scanning electron microscopy (FESEM) micrographs also show a fibrillar morphology, which is produced due to the supramolecular organization of GO-PVA complex. The highly fluorescent GO-PVA1 hybrid has been used as a fascinating tool for selective sensing of Au 3+ ions in aqueous media with a detectable limit of ∼275 ppb. The sensitivity of the Au 3+ ion (300 μM) in the presence of 600 μM concentrations of each ion (

Research paper thumbnail of Phase Behavior of Poly(vinylidene fluoride)-graft-poly(diethylene glycol methyl ether methacrylate) in Alcohol-Water System: Coexistence of LCST and UCST

The journal of physical chemistry. B, Jan 10, 2016

A thermoresponsive polymer poly(diethylene glycol methyl ether methacrylate) (PMeO2MA) is grafted... more A thermoresponsive polymer poly(diethylene glycol methyl ether methacrylate) (PMeO2MA) is grafted from poly(vinylidene fluoride) (PVDF) backbone by using a combined ATRC and ATRP technique with a high conversion (69%) of the monomer to produce the graft copolymer (PD). It is highly soluble polymer and its solution property is studied by varying polarity in pure solvents (water, methanol, isopropanol) and also in mixed solvents (water-methanol and water-isopropanol) by measuring the hydrodynamic size (Z-average) of the particles by dynamic light scattering (DLS). The variation of Z-average size with temperature of the PD solution (0.2%, w/v) indicates a lower critical solution temperature (LCST)-type phase transition (T(PL)) in aqueous medium, an upper critical solution temperature (UCST)-type phase transition (T(PU)) in isopropanol medium, and no such phase transition for methanol solution. In the mixed solvent (water + isopropanol) at 0-20% (v/v) isopropanol the TPL increases, wher...

Research paper thumbnail of Supramolecular grafting of doped polyaniline leads to an unprecedented solubility enhancement, radical cation stabilization, and morphology transformation

Journal of Materials Chemistry A, 2018

Polyaniline supramolecularly grafted with polyethylene glycol coupled with β-cyclodextrin forming... more Polyaniline supramolecularly grafted with polyethylene glycol coupled with β-cyclodextrin forming a pseudorotaxane structure shows an extremely high solubility, higher degree of doping, and highly efficient radical cation stabilization.

Research paper thumbnail of Multi-functional poly(vinylidene fluoride) graft copolymers

Journal of Polymer Science Part A: Polymer Chemistry, 2017

Poly(vinylidene fluoride) (PVDF) is known for its biocompatibility, piezo and pyro-electricity, a... more Poly(vinylidene fluoride) (PVDF) is known for its biocompatibility, piezo and pyro-electricity, and membrane forming capability. In order to tune its properties, modification through grafting from approach by atom transfer radical polymerization (ATRP) is preferred. Hydrophilic polymers like poly(ethylene glycol) methacrylate, poly(methacrylic acid), poly(dimethylaminoethyl methacrylate) (PDMAEMA), and so forth have been anchored from PVDF backbone in order to make permeation of water molecules through the PVDF based membranes. The successful solution grafting of PDMAEMA chains from PVDF backbone by ATRP resulted appreciable graft conversion and hence its bulk properties showed a significant change. This water soluble graft copolymer shows incredible mechanical and adhesive properties. PVDF-g-poly(n-butyl methacrylate) generates honeycomb porous film using "breath figure" technique. Recently, they have used further improvement of grafting where model ATRP initiators are anchored using atom transfer radical coupling and used them as macroinitiators for grafting. This approach simplified the grafting reactions even more and enabled successful grafting of a large number of monomers under relatively less drastic conditions with appreciable conversion compared with the previous conditions. This technique has resulted interesting solution properties, ion and electron conducting PVDF, antifouling membrane, super glue and super tough materials, capable of generating metal nanoparticles tunable with pH and temperature. V

Research paper thumbnail of pH and temperature responsiveness in AgNPs stabilized by a new poly(vinylidene fluoride) random graft copolymer

Journal of Polymer Science Part A: Polymer Chemistry, 2017

Poly(vinylidene fluoride)(PVDF)-graft-random copolymers(PD) of diethyleneglycol methylether metha... more Poly(vinylidene fluoride)(PVDF)-graft-random copolymers(PD) of diethyleneglycol methylether methacrylate(MeO 2 MA) and dimethylaminoethyl methacrylate(DMAEMA) are synthesized by a combined atom transfer radical coupling and atom transfer radical polymerization technique at three different co-monomer compositions. The molar ratio of MeO 2 MA to DMAEMA in PD are measured to be 1:5.8, 1:1.3, and 1:0.5 for PD1, PD2, and PD3 graft copolymers. In PD2 the feed ratio and mole ratio are same indicating an azeotropic composition causing highest yield (89%) and highest molecular weight (9.29 3 10 5). The grafted chains of PD are temperature and pH responsive and in basic pH they show a sudden increase in size above certain temperature for LCST-type phase transition, however, this is not observed at pH 4 and 7. PD can generate AgNPs under UV irradiation and morphology of PD at 30 8C varies with pH from vesicle to nanosphere. The AgNPs lie on the surface of the vesicles or assemble with the PD chains forming nanosphere morphology. At different pH, PD samples exhibit plasmon peaks at different wavelengths attributed to various size, shapes and cluster formation. The UV-vis spectra of AgNPs stabilized by PD1 and PD2 samples exhibits similar LCST-type phase transition as observed above, but that of PD3 does not show any such transition. V

Research paper thumbnail of Deciphering the Effect of Polymer-Assisted Doping on the Optoelectronic Properties of Block Copolymer-Anchored Graphene Oxide

Research paper thumbnail of An insight into the schizophrenic self-assembly of thermo and proton sensitive graphene oxide grafted block copolymer

Journal of Polymer Science Part A: Polymer Chemistry, 2016

In order to study the self-assembly of block copolymer grafted from graphene oxide (GO) by the fl... more In order to study the self-assembly of block copolymer grafted from graphene oxide (GO) by the fluorescence of GO, poly(e-caprolactone) (PCL)-block-poly(dimethyl aminoethyl methacrylate) (PDMAEMA) is grafted from its surface using consecutive ring opening (ROP) and atom transfer radical polymerization (ATRP). GO-g-(PCL 13-b-PDMAEMA 117) (GPCLD) at pH 9.2 exhibits cloud point (T c) at 32 8C. At pH 9.2 HRTEM images indicate schizophrenic morphology from vesicle at 26 8C to annular ring at 30 8C followed by giant size aggregation at 38 8C. But the reference block copolymer (PCL 14-b-PDMAEMA 126 , PCLD), synthesized using benzyl alcohol as ROP initiator, exhibits only core-shell morphology whose size increases with rising temperature at pH 9.2. GPCLD solution exhibits good photoluminescence (PL) property arising from GO at pH 9.2 and PL-intensity increases abruptly during phase transition. Both T c and size of GPCLD assembly can be reversibly tuned by CO 2 and N 2 gas purging. 1 H NMR spectra exhibit a gradual shift of resonance peaks of the protons on CO 2 bubbling. Thus at pH 9.2 and at 38 8C the GPCLD acts as a good CO 2 sensor. Additionally, the GPCLD vesicle can load hydrophobic guest molecules which can be released by triggering with CO 2. V

Research paper thumbnail of Optoelectronic and photovoltaic properties of graphene quantum dot–polyaniline nanostructures

Journal of Materials Chemistry A, 2015

In aqueous dispersions of graphene quantum dots (GQDs), aniline is in situ polymerized to produce... more In aqueous dispersions of graphene quantum dots (GQDs), aniline is in situ polymerized to produce polyaniline-GQDs hybrids and dye-sensitized solar cells fabricated with the hybrids indicate highest power conversion efficiency of 3.12%.

Research paper thumbnail of Temperature triggered antifouling properties of poly(vinylidene fluoride) graft copolymers with tunable hydrophilicity

Journal of Materials Chemistry A, 2015

PVDF-g-PMeO2MA produced by combined ATRC and ATRP methods exhibits a tuneable LCST with graft com... more PVDF-g-PMeO2MA produced by combined ATRC and ATRP methods exhibits a tuneable LCST with graft composition and a temperature triggered antifouling property.

Research paper thumbnail of Amphiphilic poly(N-vinyl pyrrolidone) grafted graphene by reversible addition and fragmentation polymerization and the reinforcement of poly(vinyl acetate) films

Journal of Materials Chemistry A, 2013

ABSTRACT The reversible addition and fragmentation (RAFT) polymerization of vinyl pyrrolidone (VP... more ABSTRACT The reversible addition and fragmentation (RAFT) polymerization of vinyl pyrrolidone (VP) from graphene oxide (GO) is used to produce GO-g-PVP (GP) and the grafting is confirmed from Fourier transformed infrared (FTIR) and nuclear magnetic resonance spectra. The average thickness of GP (8.2 nm) obtained from atomic force microscopy is higher than that of GO (1.2 nm), indicating the wrapping of grafted PVP on the GO sheets. Transmission electron microscopy of GP exhibits swollen domains (white spots) characterizing the grafted PVP chains from the GO surface. The dispersibility of the GP sheets becomes greatly improved over that of GO and they are dispersible in the solvents of Hansen solubility parameter (δp + δH) range 6.3–58. Three nanocomposites GP1, GP3 and GP5, produced by mixing with 1, 3 and 5 (w/w)% GP with poly(vinyl acetate) (PVAc), produce a stable dispersion in dimethyl formamide, although mixtures of GO and PVAc do not. The field emission scanning electron microscopy of the GP5 sample indicates a good homogeneous dispersion of GP sheets within the PVAc matrix, although both GO and PVP are individually immiscible with PVAc. The FTIR data indicates a specific interaction between GP and PVAc. The glass transition temperature (Tg) of the pure PVAc increases in the GP composites, but in the GO composite it remains unchanged. In the GPP5 hybrid containing the GO, PVP and PVAc mixture produced at the same composition as in GP5, an increase of Tg is seen to a lesser degree than that of GP, indicating that GO acts as a compatibilizer of a PVP and PVAc immiscible blend. The mechanical properties of PVAc exhibit a strong reinforcement and the Young's modulus & tensile strength data show a 190% and 169% increase over PVAc in the GP5 sample due to the homogenous dispersion and unidirectional (parallel) orientation of GP sheets in the composite film.

Research paper thumbnail of On the pH sensitive optoelectronic properties of amphiphilic reduced graphene oxide via grafting of poly(dimethylaminoethyl methacrylate): a signature of p- and n-type doping

J. Mater. Chem. A, 2014

ABSTRACT Poly(N,N′-dimethylaminoethyl methacraylate) (PDMAEMA) functionalized reduced graphene ox... more ABSTRACT Poly(N,N′-dimethylaminoethyl methacraylate) (PDMAEMA) functionalized reduced graphene oxide (rGO) is synthesized by atom transfer radical polymerization, followed by attachment to rGO via diazonium coupling. The rGO-PDMAEMA (RGP) is characterized by 1H NMR, UV-Vis, FTIR and Raman spectroscopy. TEM and AFM studies demonstrate the formation of molecular brushes of PDMAEMA chains over rGO surface, and the TGA thermograms indicate 55 wt% grafting of PDMAEMA. RGP is dispersible in the widest spectrum of solvents from CCl4 to water [solubility parameter (δp + δh), 0.6 to 58]. RGP exhibits strongly pH dependent fluorescence properties: at pH 4, it exhibits two emission peaks, but at pH 7 and pH 9.2, a single and broad emission peak is observed. Two emission peaks at pH 4 are attributed to radiative decay of excitons to two kinds of holes in the rGO originating from illumination and p-type doping, which is also characterized by a blue shift of the Raman D band. Moreover, n-type doping of RGP at pH 9.2 is also evident due to a similar Raman shift. The dc-conductivity of RGP at pH 4 is 2 orders higher than that of pH 9.2 and the I–V characteristic curve at pH 7 exhibits a bimodal NDR property with a rectification ratio of 5.5. The bimodal NDR property is explained with a model using density of states and polaronic band.

Research paper thumbnail of Coupled atom transfer radical coupling and atom transfer radical polymerization approach for controlled grafting from poly(vinylidene fluoride) backbone

Journal of Polymer Science Part A: Polymer Chemistry, 2013

A new "grafting from" strategy for grafting of different monomers (methacrylates, acrylates, and ... more A new "grafting from" strategy for grafting of different monomers (methacrylates, acrylates, and acrylamide) on poly(vinylidene fluoride) (PVDF) backbone is designed using atom transfer radical coupling (ATRC) and atom transfer radical polymerization (ATRP). 4-Hydroxy TEMPO moieties are anchored on PVDF backbone by ATRC followed by attachment of ATRP initiating sites chosen according to the reactivity of different monomers. High graft conversion is achieved and grafting of poly(methyl methacrylate) (PMMA) exhibits high degree of polymerization (DPn 5 770) with a very low graft density (0.18 per hundred VDF units) which has been increased to 0.44 by regenerating the active catalyst with the addition of Cu(0). A significant impact on thermal and stress-strain property of graft copolymers on the graft density and graft length is noted. Higher tensile strain and toughness are observed for PVDF-g-PMMA produced from model initiator but graft copolymer from pure PVDF exhibits higher tensile strength and Young's modulus. V

Research paper thumbnail of Highly Fluorescent Graphene Oxide-Poly(vinyl alcohol) Hybrid: An Effective Material for Specific Au3+ Ion Sensors

ACS Applied Materials & Interfaces, 2012

We have developed a new highly fluorescent graphene oxide (GO)/poly(vinyl alcohol) (PVA) hybrid (... more We have developed a new highly fluorescent graphene oxide (GO)/poly(vinyl alcohol) (PVA) hybrid (GO-PVA) in an acidic medium (pH 4). Fourier transform infrared (FTIR) spectra indicate the formation of hydrogen bonds between the hydroxy group of PVA and the hydroxy groups of GO. The hybrid is highly fluorescent, because of passivation by hydrogen bonding, as evident from Raman spectra. The quantum yields of GO-PVA hybrids are higher than that of GO. The fluorescent microscopic images of the hybrids exhibit a fibrillar morphology, and all of them emit highly intense green light. Field-emission scanning electron microscopy (FESEM) micrographs also show a fibrillar morphology, which is produced due to the supramolecular organization of GO-PVA complex. The highly fluorescent GO-PVA1 hybrid has been used as a fascinating tool for selective sensing of Au 3+ ions in aqueous media with a detectable limit of ∼275 ppb. The sensitivity of the Au 3+ ion (300 μM) in the presence of 600 μM concentrations of each ion (

Research paper thumbnail of Phase Behavior of Poly(vinylidene fluoride)-graft-poly(diethylene glycol methyl ether methacrylate) in Alcohol-Water System: Coexistence of LCST and UCST

The journal of physical chemistry. B, Jan 10, 2016

A thermoresponsive polymer poly(diethylene glycol methyl ether methacrylate) (PMeO2MA) is grafted... more A thermoresponsive polymer poly(diethylene glycol methyl ether methacrylate) (PMeO2MA) is grafted from poly(vinylidene fluoride) (PVDF) backbone by using a combined ATRC and ATRP technique with a high conversion (69%) of the monomer to produce the graft copolymer (PD). It is highly soluble polymer and its solution property is studied by varying polarity in pure solvents (water, methanol, isopropanol) and also in mixed solvents (water-methanol and water-isopropanol) by measuring the hydrodynamic size (Z-average) of the particles by dynamic light scattering (DLS). The variation of Z-average size with temperature of the PD solution (0.2%, w/v) indicates a lower critical solution temperature (LCST)-type phase transition (T(PL)) in aqueous medium, an upper critical solution temperature (UCST)-type phase transition (T(PU)) in isopropanol medium, and no such phase transition for methanol solution. In the mixed solvent (water + isopropanol) at 0-20% (v/v) isopropanol the TPL increases, wher...