Goutam Bit - Academia.edu (original) (raw)

Papers by Goutam Bit

Research paper thumbnail of Free radical cross-linking copolymerization of acrylamide and N,N / methylene-bis- acrylamide by using Fe(III)/thiourea and Ce(IV)/thiourea redox initiator systems

Acrylamide (AM) and N,N / methylene-bis-acrylamide (Bis) copolymerization in water has been inves... more Acrylamide (AM) and N,N / methylene-bis-acrylamide (Bis) copolymerization in water has been investigated at a total monomer concentration (AM + Bis) of 0.4 M. Extent of conversion of monomer into polymer was measured as a function of the reaction time upto the onset of macrogelation (gelation observed visually). The critical conversion at the gel point shows a minimum at ~5.7 mol% Bis concentration for Fe(III)/thiourea (TU) redox system whereas for Ce(IV)/TU redox system it occurs at ~2.6 mol% Bis concentration. It was found that polymer formed after gel points with different Bis% were not soluble in water, acetic acid, toluene or chloroform. In the copolymerization reaction involving Fe(III)/TU redox initiator system, no induction period is observed at 50 °C. In the case of Ce(IV)/TU redox initiator system, however, a significant induction period is observed at 40 °C, which depends upon the Bis% in the monomer mixture. Unlike Fe(III)/TU, the reaction takes only a few minutes to com...

Research paper thumbnail of Micellar Shape Transition under Dilute Salt-Free Conditions: Promotion and Self-Fluorescence Monitoring of Stimuli-Responsive Viscoelasticity by 1- and 2-Naphthols

The Journal of Physical Chemistry B, May 1, 2008

Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and... more Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) micelles are studied. Stimuli-responsive viscoelastic gels of long wormlike micelles are formed at low surfactant concentrations in the presence of neutral naphthols, where H-bonding plays a key role in micellar shape transition in the absence of any charge screening. Micelle-embedded naphthols also act as novel self-fluorescence probes for monitoring viscoelasticity of the system as a function of applied shear. 1H NMR study shows that the solubilization sites of naphthols in the micelle are located near the surface. While UV absorption and Fourier transform infrared studies confirm the presence of intermolecular H-bonds in micelle embedded naphthols, transmission electron micrographs of vacuum-dried samples at room temperature demonstrate the transition in shape from sphere to rodlike micelles.

Research paper thumbnail of Free radical cross-linking copolymerization of acrylamide and N,N'methylene-bisacrylamide by using Fe(III)/thiourea and Ce(IV)/thiourea redox initiator systems

Indian Journal of Chemical Technology, 2009

Research paper thumbnail of Micellar Shape Transition under Dilute Salt-Free Conditions:  Promotion and Self-Fluorescence Monitoring of Stimuli-Responsive Viscoelasticity by 1- and 2-Naphthols

The Journal of Physical Chemistry B, 2008

Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and... more Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) micelles are studied. Stimuli-responsive viscoelastic gels of long wormlike micelles are formed at low surfactant concentrations in the presence of neutral naphthols, where H-bonding plays a key role in micellar shape transition in the absence of any charge screening. Micelle-embedded naphthols also act as novel self-fluorescence probes for monitoring viscoelasticity of the system as a function of applied shear. 1H NMR study shows that the solubilization sites of naphthols in the micelle are located near the surface. While UV absorption and Fourier transform infrared studies confirm the presence of intermolecular H-bonds in micelle embedded naphthols, transmission electron micrographs of vacuum-dried samples at room temperature demonstrate the transition in shape from sphere to rodlike micelles.

Research paper thumbnail of Free-radical cross-linking copolymerization of methyl methacrylate and ethylene glycol dimethacrylate in the presence of trimethoxyvinylsilane

Journal of Physics and Chemistry of Solids, 2008

Research paper thumbnail of Molecular Dimension and Interaction Parameters of Polyacrylamide in Water‐N,N‐Dimethylformamide Mixtures

Journal of Macromolecular Science, Part A, 2005

The intrinsic viscosities [η] of polyacrylamide (PAM) having different average molecular weights ... more The intrinsic viscosities [η] of polyacrylamide (PAM) having different average molecular weights are measured in various mixtures of water (good solvent) and N, N dimethyl formamide (DMF, nonsolvent) at different temperatures. The observed results show a significant variation of cosolvency as a function of solvent composition (ϕDMF). The nature of curves in [η] vs. ϕDMF plot at different temperatures indicates

Research paper thumbnail of Solution Properties of a Polymer-Nonionic Surfactant Mixed System

Journal of Dispersion Science and Technology, 2010

The cooperative binding behavior of progressively hydrolyzed polyacrylamide with nonionic surfact... more The cooperative binding behavior of progressively hydrolyzed polyacrylamide with nonionic surfactant TritonX-100 (Tx-100) at different concentrations and temperatures has been studied viscometrically. The effect of polymer concentration and temperature on ...

Research paper thumbnail of Dilute solution behaviour of progressively hydrolyzed polyacrylamide in water–N,N dimethylformamide mixtures

European Polymer Journal, 2006

The intrinsic viscosities [gÕs] of anionic (hydrolyzed; low and high carboxyl content) and nonion... more The intrinsic viscosities [gÕs] of anionic (hydrolyzed; low and high carboxyl content) and nonionic polyacrylamide (unhydrolyzed) were measured in water-N, N dimethylformamide mixtures at various temperatures. Non-polyelectrolyte behavior of low carboxyl content polyacrylamide was observed in mixed solvent system. The plots of [g] vs. solvent composition in a mixed solvent system pass through minima for both high as well as low carboxyl content polymers but through a maximum for nonionic polyacrylamide. Observed minimum for charged polymers may be attributed to the loss of polymer sites available to interact with solvent for H-bonding interaction between neighboring amide and the acid groups. The maximum for nonionic polymer at the particular solvent composition arises for the most powerful cosolvent effect. Existence of two antagonistic effects is apparent in [g] values of nonionic polymer at various temperatures. Huggins constant (K H ) also indicates a significant variation of cosolvency as a function of solvent composition. Activation parameters of viscous flow were calculated using Frenkel-Eyring equation. The volume related parameter and the shape factor were also computed. Shape factor data indicate that polymer molecules are more or less rigid spheres and are not affected by temperature and composition of solvent.

Research paper thumbnail of Free radical cross-linking copolymerization of acrylamide and N,N / methylene-bis- acrylamide by using Fe(III)/thiourea and Ce(IV)/thiourea redox initiator systems

Acrylamide (AM) and N,N / methylene-bis-acrylamide (Bis) copolymerization in water has been inves... more Acrylamide (AM) and N,N / methylene-bis-acrylamide (Bis) copolymerization in water has been investigated at a total monomer concentration (AM + Bis) of 0.4 M. Extent of conversion of monomer into polymer was measured as a function of the reaction time upto the onset of macrogelation (gelation observed visually). The critical conversion at the gel point shows a minimum at ~5.7 mol% Bis concentration for Fe(III)/thiourea (TU) redox system whereas for Ce(IV)/TU redox system it occurs at ~2.6 mol% Bis concentration. It was found that polymer formed after gel points with different Bis% were not soluble in water, acetic acid, toluene or chloroform. In the copolymerization reaction involving Fe(III)/TU redox initiator system, no induction period is observed at 50 °C. In the case of Ce(IV)/TU redox initiator system, however, a significant induction period is observed at 40 °C, which depends upon the Bis% in the monomer mixture. Unlike Fe(III)/TU, the reaction takes only a few minutes to com...

Research paper thumbnail of Micellar Shape Transition under Dilute Salt-Free Conditions: Promotion and Self-Fluorescence Monitoring of Stimuli-Responsive Viscoelasticity by 1- and 2-Naphthols

The Journal of Physical Chemistry B, May 1, 2008

Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and... more Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) micelles are studied. Stimuli-responsive viscoelastic gels of long wormlike micelles are formed at low surfactant concentrations in the presence of neutral naphthols, where H-bonding plays a key role in micellar shape transition in the absence of any charge screening. Micelle-embedded naphthols also act as novel self-fluorescence probes for monitoring viscoelasticity of the system as a function of applied shear. 1H NMR study shows that the solubilization sites of naphthols in the micelle are located near the surface. While UV absorption and Fourier transform infrared studies confirm the presence of intermolecular H-bonds in micelle embedded naphthols, transmission electron micrographs of vacuum-dried samples at room temperature demonstrate the transition in shape from sphere to rodlike micelles.

Research paper thumbnail of Free radical cross-linking copolymerization of acrylamide and N,N'methylene-bisacrylamide by using Fe(III)/thiourea and Ce(IV)/thiourea redox initiator systems

Indian Journal of Chemical Technology, 2009

Research paper thumbnail of Micellar Shape Transition under Dilute Salt-Free Conditions:  Promotion and Self-Fluorescence Monitoring of Stimuli-Responsive Viscoelasticity by 1- and 2-Naphthols

The Journal of Physical Chemistry B, 2008

Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and... more Effect of 1 and 2-naphthols on the shape transition of cetyl trimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) micelles are studied. Stimuli-responsive viscoelastic gels of long wormlike micelles are formed at low surfactant concentrations in the presence of neutral naphthols, where H-bonding plays a key role in micellar shape transition in the absence of any charge screening. Micelle-embedded naphthols also act as novel self-fluorescence probes for monitoring viscoelasticity of the system as a function of applied shear. 1H NMR study shows that the solubilization sites of naphthols in the micelle are located near the surface. While UV absorption and Fourier transform infrared studies confirm the presence of intermolecular H-bonds in micelle embedded naphthols, transmission electron micrographs of vacuum-dried samples at room temperature demonstrate the transition in shape from sphere to rodlike micelles.

Research paper thumbnail of Free-radical cross-linking copolymerization of methyl methacrylate and ethylene glycol dimethacrylate in the presence of trimethoxyvinylsilane

Journal of Physics and Chemistry of Solids, 2008

Research paper thumbnail of Molecular Dimension and Interaction Parameters of Polyacrylamide in Water‐N,N‐Dimethylformamide Mixtures

Journal of Macromolecular Science, Part A, 2005

The intrinsic viscosities [η] of polyacrylamide (PAM) having different average molecular weights ... more The intrinsic viscosities [η] of polyacrylamide (PAM) having different average molecular weights are measured in various mixtures of water (good solvent) and N, N dimethyl formamide (DMF, nonsolvent) at different temperatures. The observed results show a significant variation of cosolvency as a function of solvent composition (ϕDMF). The nature of curves in [η] vs. ϕDMF plot at different temperatures indicates

Research paper thumbnail of Solution Properties of a Polymer-Nonionic Surfactant Mixed System

Journal of Dispersion Science and Technology, 2010

The cooperative binding behavior of progressively hydrolyzed polyacrylamide with nonionic surfact... more The cooperative binding behavior of progressively hydrolyzed polyacrylamide with nonionic surfactant TritonX-100 (Tx-100) at different concentrations and temperatures has been studied viscometrically. The effect of polymer concentration and temperature on ...

Research paper thumbnail of Dilute solution behaviour of progressively hydrolyzed polyacrylamide in water–N,N dimethylformamide mixtures

European Polymer Journal, 2006

The intrinsic viscosities [gÕs] of anionic (hydrolyzed; low and high carboxyl content) and nonion... more The intrinsic viscosities [gÕs] of anionic (hydrolyzed; low and high carboxyl content) and nonionic polyacrylamide (unhydrolyzed) were measured in water-N, N dimethylformamide mixtures at various temperatures. Non-polyelectrolyte behavior of low carboxyl content polyacrylamide was observed in mixed solvent system. The plots of [g] vs. solvent composition in a mixed solvent system pass through minima for both high as well as low carboxyl content polymers but through a maximum for nonionic polyacrylamide. Observed minimum for charged polymers may be attributed to the loss of polymer sites available to interact with solvent for H-bonding interaction between neighboring amide and the acid groups. The maximum for nonionic polymer at the particular solvent composition arises for the most powerful cosolvent effect. Existence of two antagonistic effects is apparent in [g] values of nonionic polymer at various temperatures. Huggins constant (K H ) also indicates a significant variation of cosolvency as a function of solvent composition. Activation parameters of viscous flow were calculated using Frenkel-Eyring equation. The volume related parameter and the shape factor were also computed. Shape factor data indicate that polymer molecules are more or less rigid spheres and are not affected by temperature and composition of solvent.