Jayant Kumar - Academia.edu (original) (raw)
Papers by Jayant Kumar
Synthetic Metals, 2011
Enzymatic polymerization is an environmentally friendly alternative route for the synthesis of ad... more Enzymatic polymerization is an environmentally friendly alternative route for the synthesis of advanced-functional materials. Until recently, synthetic methods for production of polypyrrole (PPy) were confined to the use of chemical oxidants or electrochemical methods. Here, we report the low temperature, oxidative polymerization of pyrrole using soybean peroxidase as the catalyst in aqueous non-toxic media. In addition to the benefits of the mild synthetic conditions, enzyme catalysis also affords PPy with fewer structural defects. Poly(sodium 4-styrenesulfonate) (PSS) was used as a charge-balancing dopant and dispersant for PPy to monitor changes in the absorption spectra of the polymer over time. However, the polymerization methodology is amenable to other dopants, including small molecule dopants like 10-camphor sulfonic acid. Spectroscopic characterization indicated that the PPy was conductive, and was produced in higher yields and at faster rates at lower temperatures. Careful temperature control combined with the appropriate choice of dopant ensured production of more electrically conductive PPy with conductivities that exceeded 3 S/cm. UV-Vis spectroscopy was used to provide evidence of favorable interactions between pyrrole and the dopant that may have facilitated the reaction. These interactions, combined with a low synthesis temperature and controlled enzyme-catalyzed radical generation, synergistically favored the formation of PPy with fewer defects and a more linear structure.
Molecular Diversity, 2000
The use of enzymes in synthetic applications has increased dramatically in the recent years and t... more The use of enzymes in synthetic applications has increased dramatically in the recent years and the field of polymer science is part of this trend. Synthesis of a variety of polymers using lipase catalyzed (Candida antarctica) polymerization reactions has led to a variety of new materials with interesting properties in our laboratories. This paper describes the synthesis of multi-component polyesters and mixed polymers having polyester and polyamide linkages under solvent-less conditions using Candida antarctica lipase B. The effect of a third component, i.e. a series
MRS Proceedings, 2007
ABSTRACTA novel biomimetic route for the synthesis of conducting homopolymers and copolymers from... more ABSTRACTA novel biomimetic route for the synthesis of conducting homopolymers and copolymers from aniline, phenol, pyrrole and 3,4-ethylenedioxy-thiophene in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS) is presented. A poly(ethylene glycol) modified hematin (PEG-Hematin) and the enzyme horseradish peroxidase (HRP) were used to catalyze the copolymerization of different monomers. UV-vis, FTIR, XPS, TGA and electrical conductivity studies for all complexes indicated the presence of a stable and electrically conductive form of these polymers. Furthermore, the presence of a polyelectrolyte, such as SPS, in this complex provides a unique combination of properties such as processability and water-solubility. Additionally catechins, the active compounds found in green tea, were polymerized and found to exhibit very interesting anti-carcinogenic properties. Here we report a unique enzymatic approach for the synthesis of water-soluble poly(catechins) with enhanced s...
Sensors and Actuators A: Physical, 2011
We report on the use of electrospun nanofibrous film for surface acoustic wave (SAW) sensors to e... more We report on the use of electrospun nanofibrous film for surface acoustic wave (SAW) sensors to enhance its chemical detection capability. Ultrafine (100-300 nm) polyethylene oxide (PEO) fibers with controlled thickness and porosity were electrospun-coated on the surface of a ST-cut quartz SAW sensor. The nanofibrous film provides a high surface area to volume ratio, which can not only offer more adsorption sites for vapor molecules, but also shortens the diffusion length of vapor molecules into polymer material. Compared to conventional thin film coating techniques, the nanofiber-coated SAW sensor shows a higher sensitivity and faster response (shorter adsorption/desorption times). In addition, a theoretical analysis was performed to understand SAW sensor response with nanofibrous film coating. It is concluded that the nanofiber film holds a great potential in enhancing SAW sensor performance for trace level detection of chemical analytes.
Polymer Engineering & Science, 2006
The fundamental properties of pure poly(3,4-thylenedioxythiophene) (PEDOT), one of the most commo... more The fundamental properties of pure poly(3,4-thylenedioxythiophene) (PEDOT), one of the most common electrically conducting organic polymers, are the key to the development of more prominent applications in which PEDOT and its derivatives can be utilized. Conducting molecular complex of PEDOT with silica was synthesized in the presence of charged silica template by the in situ biomimetic polymerization. To remove silica from PEDOT/template complex, hydrofluoric acid was used to etch silica particles. The electrochemical, thermal, and optical properties of pure PEDOT recovered were investigated in comparison with those of EDOT monomer or PEDOT with template by using UV–vis–near–IR spectra, cyclic voltammetry, thermogravimetric analysis, and fluorescence spectra. POLYM. ENG. SCI., 47:71–75, 2007. © 2006 Society of Plastics Engineers
Organic Electronics, 2006
Solid state dye-sensitized solar cells were fabricated using polydiacetylene as the hole transpor... more Solid state dye-sensitized solar cells were fabricated using polydiacetylene as the hole transport material. The polydiacetylene was incorporated into the nanoporous TiO 2 film by solution casting of an amphiphilic diacetylene and subsequent in situ polymerization. Polydiacetylenes as prepared via solid state polymerization are crystalline, exhibiting high charge carrier mobility. Our preliminary experiments demonstrated a short-circuit current density of 3.73 mA/cm 2 and an overall power conversion efficiency of 0.62% under AM 1.5 illumination (100 mW/cm 2).
Nano Letters, 2004
We report a new fabrication approach to highly sensitive optical sensors by combining the techniq... more We report a new fabrication approach to highly sensitive optical sensors by combining the techniques of electrospinning and electrostatic layer-by-layer adsorption. A fluorescent probe, hydrolyzed poly[2-(3-thienyl) ethanol butoxy carbonyl-methyl urethane] (H-PURET), was electrostatically assembled onto the surface of cellulose acetate (CA) electrospun nanofibrous membranes. The fluorescence of these membranes can be quenched by extremely low concentrations (ppb) of methyl viologen (MV 2+) and cytochrome c (cyt c) in aqueous solutions. This high sensitivity is attributed to the high surface-area-to-volume ratio of the electrospun membranes and efficient interaction between the fluorescent conjugated polymer and the analytes.
Macromolecular Chemistry and Physics, 2010
Pyrrole/EDOT copolymers were synthesized using environmentally benign enzyme catalysis. PSS was u... more Pyrrole/EDOT copolymers were synthesized using environmentally benign enzyme catalysis. PSS was used as the solubilizing template and charge-balancing dopant. Soybean peroxidase was utilized as a catalyst for the copolymerization reactions to yield poly(pyrrole-EDOT)/PSS complex. Systematic studies were conducted with varying monomer feed ratios, temperature, and pH. Here we report for the first time, the enzyme catalyzed polymerization of pyrrole and EDOT at an elevated pH ¼ 5. The polymer composition was determined using X-ray photoelectron spectroscopy. Spectroscopic characterization [UV-Vis, FTIR], thermal analysis, and electrical conductivity measurements for these complexes indicated the formation of stable conducting copolymers. Chemical Synthesis of Copolymers Pyrrole/EDOT copolymers were chemically synthesized using literature protocol reported for the chemical synthesis of pyrrole Soybean Peroxidase Catalyzed Enzymatic Synthesis of. . .
Journal of Materials Chemistry, 2008
ABSTRACT A simple and low cost methodology for fabricating one and two dimensional periodic ZnOna... more ABSTRACT A simple and low cost methodology for fabricating one and two dimensional periodic ZnOnanostructures utilizing surface relief patterns on azopolymer films as templates is demonstrated.
Journal of Macromolecular Science, Part A, 2008
Page 1. Journal of Macromolecular ScienceR , Part A: Pure and Applied Chemistry (2008) 45, 95195... more Page 1. Journal of Macromolecular ScienceR , Part A: Pure and Applied Chemistry (2008) 45, 951956 Copyright C Taylor & Francis Group, LLC ISSN: 1060-1325 print / 1520-5738 online DOI: 10.1080/10601320802380232 Biocatalytic Modification of Naturally Occurring Iron ...
Chemistry of Materials, 1997
Two types of new nonlinear optical polymers have been synthesized by postreaction of an epoxy-bas... more Two types of new nonlinear optical polymers have been synthesized by postreaction of an epoxy-based polymer prepared from the diglycidyl ether of bisphenol A and aniline. The new polymers DGEBA-AZO-TCV and DGEBA-AN-TCV were synthesized by azo coupling of the epoxy polymer with 4-(tricyanovinyl)aniline and by reacting the epoxy polymer with tetracyanoethylene, respectively. Using an azo coupling reaction to functionalize the polymer allows introduction of the tricyanovinyl (TCV) group and extension of the conjugation length to take place in a single-step reaction. In both synthetic routes, TCV groups are introduced at the last stage of the polymer preparation, thus preventing the exposure of the TCV chromophores to harsh reaction conditions. The d 33 values for polymers DGEBA-AN-TCV and DGEBA-AZO-TCV were determined to be 27 and 66 pm/V at 1.542 µm, respectively, after corona poling. The two polymers retained 65% and 83% of the initial d 33 values after they had been heated at 80°C for 1000 h.
Bioorganic & Medicinal Chemistry, 2003
Eleven (+/-)-5/6/7-acetoxy-4-aryl-3,4-dihydrocoumarins have been synthesised in two steps startin... more Eleven (+/-)-5/6/7-acetoxy-4-aryl-3,4-dihydrocoumarins have been synthesised in two steps starting from the coupling of cinnamic acid/substituted cinnamic acid with appropriate phenols, followed by acetylation in 50-83% overall yields. All hydroxy- and acetoxycoumarins were unambiguously identified on the basis of their spectral data. Candida antarctica lipase-catalysed deacetylation of these racemic acetoxydihydrocoumarins in dioxane occurred with moderate enantioselectivity. This is one of the rare examples of resolution using phenolic ester moiety as a remote handle for chiral recognition by a lipase.
Advanced Materials, 2000
cling of these compounds involves the insertion and de-insertion of cations during reduction and ... more cling of these compounds involves the insertion and de-insertion of cations during reduction and oxidation, respectively. It has also been demonstrated that the incorporation of [Co(C 2 B 9 H 11) 2 ] ± in the polypyrrole material has dramatically improved its overoxidation threshold, as compared with commonly used doping anions. Also, the thermal properties of the material have improved, or at least not deteriorated, as a result of the incorporation of [Co(C 2 B 9 H 11) 2 ] ±. Finally, it has been demonstrated that [Co(C 2 B 9 H 11) 2 ] ± is uniformly distributed on the surface. An in-depth analysis has been carried out with argon-ion sputtering with no special experimental difficulties, demonstrating for the first time uniform distribution of the doping agent through the whole thickness of the material. Some physical properties must be attributed to the unique nature of these low-density, low-coordinating, low-nucleophilic anions, but some may be attributed to the large boron presence in the material.
Synthetic Metals, 2011
Enzymatic polymerization is an environmentally friendly alternative route for the synthesis of ad... more Enzymatic polymerization is an environmentally friendly alternative route for the synthesis of advanced-functional materials. Until recently, synthetic methods for production of polypyrrole (PPy) were confined to the use of chemical oxidants or electrochemical methods. Here, we report the low temperature, oxidative polymerization of pyrrole using soybean peroxidase as the catalyst in aqueous non-toxic media. In addition to the benefits of the mild synthetic conditions, enzyme catalysis also affords PPy with fewer structural defects. Poly(sodium 4-styrenesulfonate) (PSS) was used as a charge-balancing dopant and dispersant for PPy to monitor changes in the absorption spectra of the polymer over time. However, the polymerization methodology is amenable to other dopants, including small molecule dopants like 10-camphor sulfonic acid. Spectroscopic characterization indicated that the PPy was conductive, and was produced in higher yields and at faster rates at lower temperatures. Careful temperature control combined with the appropriate choice of dopant ensured production of more electrically conductive PPy with conductivities that exceeded 3 S/cm. UV-Vis spectroscopy was used to provide evidence of favorable interactions between pyrrole and the dopant that may have facilitated the reaction. These interactions, combined with a low synthesis temperature and controlled enzyme-catalyzed radical generation, synergistically favored the formation of PPy with fewer defects and a more linear structure.
Molecular Diversity, 2000
The use of enzymes in synthetic applications has increased dramatically in the recent years and t... more The use of enzymes in synthetic applications has increased dramatically in the recent years and the field of polymer science is part of this trend. Synthesis of a variety of polymers using lipase catalyzed (Candida antarctica) polymerization reactions has led to a variety of new materials with interesting properties in our laboratories. This paper describes the synthesis of multi-component polyesters and mixed polymers having polyester and polyamide linkages under solvent-less conditions using Candida antarctica lipase B. The effect of a third component, i.e. a series
MRS Proceedings, 2007
ABSTRACTA novel biomimetic route for the synthesis of conducting homopolymers and copolymers from... more ABSTRACTA novel biomimetic route for the synthesis of conducting homopolymers and copolymers from aniline, phenol, pyrrole and 3,4-ethylenedioxy-thiophene in the presence of a polyelectrolyte, such as polystyrene sulfonate (SPS) is presented. A poly(ethylene glycol) modified hematin (PEG-Hematin) and the enzyme horseradish peroxidase (HRP) were used to catalyze the copolymerization of different monomers. UV-vis, FTIR, XPS, TGA and electrical conductivity studies for all complexes indicated the presence of a stable and electrically conductive form of these polymers. Furthermore, the presence of a polyelectrolyte, such as SPS, in this complex provides a unique combination of properties such as processability and water-solubility. Additionally catechins, the active compounds found in green tea, were polymerized and found to exhibit very interesting anti-carcinogenic properties. Here we report a unique enzymatic approach for the synthesis of water-soluble poly(catechins) with enhanced s...
Sensors and Actuators A: Physical, 2011
We report on the use of electrospun nanofibrous film for surface acoustic wave (SAW) sensors to e... more We report on the use of electrospun nanofibrous film for surface acoustic wave (SAW) sensors to enhance its chemical detection capability. Ultrafine (100-300 nm) polyethylene oxide (PEO) fibers with controlled thickness and porosity were electrospun-coated on the surface of a ST-cut quartz SAW sensor. The nanofibrous film provides a high surface area to volume ratio, which can not only offer more adsorption sites for vapor molecules, but also shortens the diffusion length of vapor molecules into polymer material. Compared to conventional thin film coating techniques, the nanofiber-coated SAW sensor shows a higher sensitivity and faster response (shorter adsorption/desorption times). In addition, a theoretical analysis was performed to understand SAW sensor response with nanofibrous film coating. It is concluded that the nanofiber film holds a great potential in enhancing SAW sensor performance for trace level detection of chemical analytes.
Polymer Engineering & Science, 2006
The fundamental properties of pure poly(3,4-thylenedioxythiophene) (PEDOT), one of the most commo... more The fundamental properties of pure poly(3,4-thylenedioxythiophene) (PEDOT), one of the most common electrically conducting organic polymers, are the key to the development of more prominent applications in which PEDOT and its derivatives can be utilized. Conducting molecular complex of PEDOT with silica was synthesized in the presence of charged silica template by the in situ biomimetic polymerization. To remove silica from PEDOT/template complex, hydrofluoric acid was used to etch silica particles. The electrochemical, thermal, and optical properties of pure PEDOT recovered were investigated in comparison with those of EDOT monomer or PEDOT with template by using UV–vis–near–IR spectra, cyclic voltammetry, thermogravimetric analysis, and fluorescence spectra. POLYM. ENG. SCI., 47:71–75, 2007. © 2006 Society of Plastics Engineers
Organic Electronics, 2006
Solid state dye-sensitized solar cells were fabricated using polydiacetylene as the hole transpor... more Solid state dye-sensitized solar cells were fabricated using polydiacetylene as the hole transport material. The polydiacetylene was incorporated into the nanoporous TiO 2 film by solution casting of an amphiphilic diacetylene and subsequent in situ polymerization. Polydiacetylenes as prepared via solid state polymerization are crystalline, exhibiting high charge carrier mobility. Our preliminary experiments demonstrated a short-circuit current density of 3.73 mA/cm 2 and an overall power conversion efficiency of 0.62% under AM 1.5 illumination (100 mW/cm 2).
Nano Letters, 2004
We report a new fabrication approach to highly sensitive optical sensors by combining the techniq... more We report a new fabrication approach to highly sensitive optical sensors by combining the techniques of electrospinning and electrostatic layer-by-layer adsorption. A fluorescent probe, hydrolyzed poly[2-(3-thienyl) ethanol butoxy carbonyl-methyl urethane] (H-PURET), was electrostatically assembled onto the surface of cellulose acetate (CA) electrospun nanofibrous membranes. The fluorescence of these membranes can be quenched by extremely low concentrations (ppb) of methyl viologen (MV 2+) and cytochrome c (cyt c) in aqueous solutions. This high sensitivity is attributed to the high surface-area-to-volume ratio of the electrospun membranes and efficient interaction between the fluorescent conjugated polymer and the analytes.
Macromolecular Chemistry and Physics, 2010
Pyrrole/EDOT copolymers were synthesized using environmentally benign enzyme catalysis. PSS was u... more Pyrrole/EDOT copolymers were synthesized using environmentally benign enzyme catalysis. PSS was used as the solubilizing template and charge-balancing dopant. Soybean peroxidase was utilized as a catalyst for the copolymerization reactions to yield poly(pyrrole-EDOT)/PSS complex. Systematic studies were conducted with varying monomer feed ratios, temperature, and pH. Here we report for the first time, the enzyme catalyzed polymerization of pyrrole and EDOT at an elevated pH ¼ 5. The polymer composition was determined using X-ray photoelectron spectroscopy. Spectroscopic characterization [UV-Vis, FTIR], thermal analysis, and electrical conductivity measurements for these complexes indicated the formation of stable conducting copolymers. Chemical Synthesis of Copolymers Pyrrole/EDOT copolymers were chemically synthesized using literature protocol reported for the chemical synthesis of pyrrole Soybean Peroxidase Catalyzed Enzymatic Synthesis of. . .
Journal of Materials Chemistry, 2008
ABSTRACT A simple and low cost methodology for fabricating one and two dimensional periodic ZnOna... more ABSTRACT A simple and low cost methodology for fabricating one and two dimensional periodic ZnOnanostructures utilizing surface relief patterns on azopolymer films as templates is demonstrated.
Journal of Macromolecular Science, Part A, 2008
Page 1. Journal of Macromolecular ScienceR , Part A: Pure and Applied Chemistry (2008) 45, 95195... more Page 1. Journal of Macromolecular ScienceR , Part A: Pure and Applied Chemistry (2008) 45, 951956 Copyright C Taylor & Francis Group, LLC ISSN: 1060-1325 print / 1520-5738 online DOI: 10.1080/10601320802380232 Biocatalytic Modification of Naturally Occurring Iron ...
Chemistry of Materials, 1997
Two types of new nonlinear optical polymers have been synthesized by postreaction of an epoxy-bas... more Two types of new nonlinear optical polymers have been synthesized by postreaction of an epoxy-based polymer prepared from the diglycidyl ether of bisphenol A and aniline. The new polymers DGEBA-AZO-TCV and DGEBA-AN-TCV were synthesized by azo coupling of the epoxy polymer with 4-(tricyanovinyl)aniline and by reacting the epoxy polymer with tetracyanoethylene, respectively. Using an azo coupling reaction to functionalize the polymer allows introduction of the tricyanovinyl (TCV) group and extension of the conjugation length to take place in a single-step reaction. In both synthetic routes, TCV groups are introduced at the last stage of the polymer preparation, thus preventing the exposure of the TCV chromophores to harsh reaction conditions. The d 33 values for polymers DGEBA-AN-TCV and DGEBA-AZO-TCV were determined to be 27 and 66 pm/V at 1.542 µm, respectively, after corona poling. The two polymers retained 65% and 83% of the initial d 33 values after they had been heated at 80°C for 1000 h.
Bioorganic & Medicinal Chemistry, 2003
Eleven (+/-)-5/6/7-acetoxy-4-aryl-3,4-dihydrocoumarins have been synthesised in two steps startin... more Eleven (+/-)-5/6/7-acetoxy-4-aryl-3,4-dihydrocoumarins have been synthesised in two steps starting from the coupling of cinnamic acid/substituted cinnamic acid with appropriate phenols, followed by acetylation in 50-83% overall yields. All hydroxy- and acetoxycoumarins were unambiguously identified on the basis of their spectral data. Candida antarctica lipase-catalysed deacetylation of these racemic acetoxydihydrocoumarins in dioxane occurred with moderate enantioselectivity. This is one of the rare examples of resolution using phenolic ester moiety as a remote handle for chiral recognition by a lipase.
Advanced Materials, 2000
cling of these compounds involves the insertion and de-insertion of cations during reduction and ... more cling of these compounds involves the insertion and de-insertion of cations during reduction and oxidation, respectively. It has also been demonstrated that the incorporation of [Co(C 2 B 9 H 11) 2 ] ± in the polypyrrole material has dramatically improved its overoxidation threshold, as compared with commonly used doping anions. Also, the thermal properties of the material have improved, or at least not deteriorated, as a result of the incorporation of [Co(C 2 B 9 H 11) 2 ] ±. Finally, it has been demonstrated that [Co(C 2 B 9 H 11) 2 ] ± is uniformly distributed on the surface. An in-depth analysis has been carried out with argon-ion sputtering with no special experimental difficulties, demonstrating for the first time uniform distribution of the doping agent through the whole thickness of the material. Some physical properties must be attributed to the unique nature of these low-density, low-coordinating, low-nucleophilic anions, but some may be attributed to the large boron presence in the material.