Mohammad Siddiq - Academia.edu (original) (raw)
Papers by Mohammad Siddiq
Journal of Inorganic and Organometallic Polymers and Materials, 2021
Lyophilic microgels based on Gum Acacia (GAC) were synthesized at room temperature and normal pre... more Lyophilic microgels based on Gum Acacia (GAC) were synthesized at room temperature and normal pressure. Briefly, high yield of the spherical shaped microgels of size ≤ 50 µm was obtained via introducing linear GAC and divinyl sulfone (DS) in the reverse micelle cores of NBSS in the stirring gasoline. The GAC microgels were then utilized as synthetic micro-templates for fabricating their nanocomposites with Cobalt (Co), to subsequently produce GAC-Co nanocomposite microgels. The as synthesis GAC based microgels and the GAC-Co microgels were characterized through FTIR, TGA, DSC, SEM, EDS, and TEM. Different amounts of GAC-Co microgels were used as nano-catalyst for the degradation of poisonous aromatic compounds and an Azo dye in aqueous medium. Briefly, 1 g GAC-Co microgels degraded 100 mL (250 ppm solution) of each the aforementioned compounds in ≤ 25 min at neutral pH. The increase in the kinetic parameter i.e., rate constant (kapp) value with increase in the GAC-Co nanocomposite m...
Microscopy Research and Technique
Catalysis Letters
Abstract Hydrogels of Acacia gum (AG) were synthesized in the reverse micelle core of sodium bis ... more Abstract Hydrogels of Acacia gum (AG) were synthesized in the reverse micelle core of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in gasoline medium. The as synthesized hydrogels were used as template to prepare Silver nanoparticle (AgNPs) in situ via the reduction mechanism of NaBH 4 . The successful synthesis of bare hydrogels and AgNPs loaded nanocomposite hydrogels (AG–Ag hydrogels) were characterized through Fourier Transform Infrared spectroscopy, Thermal gravimetric analysis, Differential Scanning Calorimetry, Scanning Electron Microscopy, energy dispersive X-ray spectroscopy and Transmission Electron Microscopy, and Atomic Absorption Spectroscopy (AAS). Different feeds of the as fabricated GA-Ag hydrogels were used to catalyze the well-known reactions of 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), and Methyl Orange (MO) reduction in aqueous medium at ambient physical conditions. Remarkably, 1000 mg/L of AG–Ag hydrogels with reduced 4-NP and 2-NP into its counterparts, 4-aminophenol and 2-aminophenol in 24 min and 15 min, respectively at room temperature. Similarly, 1000 mg/L of AG–Ag hydrogels reduced MO completely within 25 min. The aforementioned catalytic reactions followed pseudo first order rate kinetics, and it was found that the value of rate constant (kapp) increased by increasing the catalyst amount which, thereby confirms the high conversion rate of the reactants. Graphic Abstract Schematic illustration of fabrication and catalytic action of AgNPs grown inside the pre-synthesized AG Hydrogel matrices.
Iranian Polymer Journal
Well-defined amphiphilic comb-like pentablock copolymers based on Pluronic L64 (PEO13-b-PPO30-b-P... more Well-defined amphiphilic comb-like pentablock copolymers based on Pluronic L64 (PEO13-b-PPO30-b-PEO13) and poly(ethylene glycol)methyl ether methacrylate (PEGMA) have been successfully synthesized via atom transfer radical polymerization (ATRP). The L64 is transformed into ATRP macroinitiator and chain extended with PEGMA under typical ATRP conditions to achieve comb-like pentablock copolymers of various compositions. Due to their amphiphilic nature, the block copolymers could form self-assembled structures in aqueous solutions as confirmed by dynamic light scattering. At higher PEGMA content in the synthesized copolymer, however, the critical aggregation concentration (CAC) is less pronounced that could be attributed to the increased hydrophilicity and steric hindrance of PEG side chains of the PEGMA, thus preventing the formation of well-defined micellar aggregates, and probably leads to open-shell aggregation mechanism. The lower critical solution temperature (LCST) of the synthesized block copolymers is found higher than the neat L64 and increased with increasing the PEGMA content. Further, tuning the clouding behavior could be achieved with inorganic additives (KBr and K2SO4). The influence of SO42− and Br1− on LCST is according to their position in Hofmeister series. Interestingly, the effect of additives is more pronounced above the CAC of the copolymer, suggesting that the nanoaggregates in solution induce the macrophase separation.
Journal of Physics and Chemistry of Solids
Abstract A high charge-carrier transport is an important aim in the synthesis of nanostructures f... more Abstract A high charge-carrier transport is an important aim in the synthesis of nanostructures for an effective supercapacitor. This article describes a methodology to prepare mesoporous silica nanoparticles (MSNs) wrapped with graphene oxide (GO) together with conducting polyaniline (PANI) wires. The morphology and chemical structure of the prepared samples have been tested by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and X-ray diffraction (XRD), whereas the stability and electrostatic interaction of the structures have been verified by thermogravimetric analysis (TGA) and Fourier-transform infrared (FT-IR) spectroscopy, respectively. The supercapacitive behaviour of these nanocomposites has been analysed by cyclic voltammetry (CV), charge–discharge tests, and electrochemical impedance spectroscopy (EIS). Compared with pristine MSNs and PANI, the 20%-GO@MSNs/PANI nanocomposite had the highest specific capacitance, reaching 412 F g−1. The nanocomposite structure maximizes the synergy between mesoporous metal oxide, conducting PANI, and GO, yielding a significantly enhanced specific capacitance, rapid charge–discharge rates, and good cycling stability of the resulting device. The wrapping with GO prevents the structural breakdown and acts as a highly conductive pathway by bridging the individual particles, whereas the MSNs nanoparticles greatly enlarge the specific surface area to facilitate ion transport and charge transfer throughout the cycling performance of supercapacitor. The approach adopted in this article can be applied for preparing similar novel functional materials in future for electrochemical applications.
International Journal of Environmental Science and Technology
This work describes the synthesis of poly(acrylic acid) microgels and fabrication of magnetic cob... more This work describes the synthesis of poly(acrylic acid) microgels and fabrication of magnetic cobalt nanoparticles in the prepared microgels. Cobalt nanoparticles were fabricated by loading the cobalt (II) ions in microgels from aqueous solution and their subsequent reduction with sodium borohydride (NaBH4). Bare and composite microgels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The catalytic properties of the prepared microgel composites were investigated by using them as catalyst for the reduction of 4-nitrophenol and methylene blue. The effect of temperature and catalyst dose on the rate of reduction of these toxic pollutants was investigated. The reusability of prepared catalysts was also studied for the five consecutive cycles, and an increase in catalytic activity was observed after every cycle. The prepared bare and magnetic microgels were found as very effective adsorbent for the removal of methylene blue from aqueous medium. Very rapid adsorption rate was found for the removal of methylene as its 100 mg was adsorbed on per gram of dried hydrogels in about 25 min. The effects of different parameters like amount of adsorbate and concentration of adsorbent on the adsorption process were studied. Langmuir, Freundlich and Temkin adsorption isotherms were applied, and it was found that adsorption of MB follows Freundlich model better than others. Furthermore, pseudo-first-order and pseudo-second-order kinetic models were also applied and adsorption of MB was found to abide by pseudo-second-order kinetics.
New J. Chem., 2017
Active oxygen for CO oxidation over Au/TiO2 is a highly stable atomic species, which is formed at... more Active oxygen for CO oxidation over Au/TiO2 is a highly stable atomic species, which is formed at the perimeter of the Au/oxide interface.
J Appl Polym Sci, 1996
... 1996 SIDDIQ, WU, AND LI ... of gyration and average hydrody-namic radius, respectively, and w... more ... 1996 SIDDIQ, WU, AND LI ... of gyration and average hydrody-namic radius, respectively, and we also determined the calibration between the translational diffusion coefficient D and the molecular weight M for PEK-C in CHC13 at 25°C. We demonstrate that on the basis of our ...
Journal of Polymer Engineering, 2016
Copper nanoparticles (CuNPs) are formed inside a microgel assembly by an
Journal of colloid and interface science, Jan 18, 2016
In this study, the synthesis of micron-sized poly(vinylbenzyl chloride) (p(VBC)) beads and subseq... more In this study, the synthesis of micron-sized poly(vinylbenzyl chloride) (p(VBC)) beads and subsequent conversion of the reactive chloromethyl groups to double amidoxime group containing moieties by post modification is reported. The prepared beads were characterized by SEM and FT-IR spectroscopy. The amidoximated p(VBC) beads were used as adsorbent for the removal of organic dyes, such as eosin y (EY) and methyl orange (MO), and heavy metals containing complex ions such as dichromate (Cr2O7(2-)) and arsenate (HAsO4(2)(-)) from aqueous media. The effect of the adsorbent dose on the percent removal, the effect of initial concentration of adsorbates on the adsorption rate and their amounts were also investigated. The Langmuir, Freundlich and Temkin adsorption isotherms were applied to the adsorption processes. The results indicated that the adsorption of both dichromate and arsenate ions obeyed the Langmuir adsorption model. Interestingly, it was found that the prepared beads were capa...
Encyclopedia of Biomedical Polymers and Polymeric Biomaterials, 2016
Materials Chemistry and Physics, 2016
Abstract The aim of this study is to investigate the kinetics and mechanism of reduction of nitro... more Abstract The aim of this study is to investigate the kinetics and mechanism of reduction of nitrobenzene using novel silver-poly(N-isopropylacrylamide-co-allylacetic acid) hybrid microgels as catalyst. For this purpose effect of catalyst dosage, concentration of nitrobenzene, concentration of sodium borohydride (NaBH 4 ) and temperature on value of apparent rate constant (k app ) was studied. The value of k app linearly increases from 0.083 to 0.313min −1 by increasing catalyst dosage from 66.66 to 102.56 μg/L at 305 K. Initially value of k app increases with increase in concentration of NaBH 4 . After reaching maxima the value of k app decreases with increase in concentration of NaBH 4 . Similar trend in the value of k app was observed in case of nitrobenzene. Retardation in value of k app at very high concentrations of reagents indicates that catalytic reduction obeys Langmuir–Hinshelwood mechanism. k app shows non-linear dependence on temperature. Initially the value of k app increases by increasing temperature upto 308 K due to Arrhenius behavior of reaction. On further increase in temperature upto 312 K the value of k app decreases due to deswelling of hybrid microgels. While the value of k app increases again with increase in temperature above 312 K. Hybrid microgels were characterized by FTIR, DLS, TEM, XRD and UV–Visible spectroscopy.
Journal of Dispersion Science and Technology, 2015
The physicochemical investigations on the associative, micellar, and thermodynamic properties of ... more The physicochemical investigations on the associative, micellar, and thermodynamic properties of a diblock (PEO)62-b-(PBO)33 copolymer in aqueous medium and its interaction with ionic surfactants were carried out by using surface tensiometry, laser light scattering, and steady-state fluorescence spectroscopy. Surface tension and fluorescence measurements were used to find out the critical micelle concentration (CMC) and related thermodynamic parameters of micellization copolymer at various temperatures. The data from dynamic light scattering (DLS) were helpful to obtain the values of hydrodynamic radii (Rh), volume (υh), and hydrodynamic expansion parameter (δh) of the copolymer micelle. Likewise, the measurements from static light scattering (SLS) were employed to determine weight-average molar (Mw), association number (Nw), thermodynamic radius (Rt), thermodynamic volume (υt), anhydrous volume (υa), and thermodynamic expansion parameter (δt) of the copolymer micelles in the temperature range of 20–50°C. Similarly, the interactions between (PEO)62-b-(PBO)33 and two ionic surfactants, sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (CTAB), have also been investigated by fluorescence spectroscopy and DLS at 30°C. Similarly, the interactions between (PEO)62-b-(PBO)33 and two ionic surfactants, sodium dodecyl sulfate and hexadecyl trimethylammonium bromide, have also been investigated by fluorescence spectroscopy and DLS in detail. GRAPHICAL ABSTRACT
Journal of Polymer Research, 2014
This study describes the surface, micellar, associative and thermodynamic properties of four dibl... more This study describes the surface, micellar, associative and thermodynamic properties of four diblock oxyethylene (E)/oxybutylene (B) copolymers with different hydrophilic block ends and various hydrophilic/hydrophobic ratios in aqueous media. The copolymers were denoted DE 40 B 18 , TE 40 B 18 , E 56 B 19 and E 56 B 7. The aqueous polymer solutions at various concentrations and temperatures were investigated by surface tensiometry and dynamic and static laser light scattering. Surface tension measurements were employed to detect the critical micelle concentration (CMC) as well as to calculate the surface-active and thermodynamic parameters of adsorption at the air/water interface. CMC values were also used to calculate the enthalpy of micellization (ΔH 0 mic), free energy of micellization (ΔG 0 mic) and entropy of micellization (ΔS 0 mic). Similarly, various thermodynamic parameters for adsorption at the air/water interface were also deduced. Dynamic light scattering (DLS) was used to obtain the hydrodynamic radii (r h) and volumes (υ h) of the micelle at different temperatures, and hence the hydrodynamic expansion parameter (δ h) was also estimated. Likewise, static light-scattering measurements enabled us to determine various parameters of the copolymer micelles, such as the weightaverage molar mass (M w), association number (N w), thermodynamic radius (r t), thermodynamic volume (υ t), anhydrous volume (υ a) and the thermodynamic expansion parameter (δ t). Various thermodynamic and micellar parameters obtained from light scattering show that the micelles formed are spherical in shape and have rather soft interaction potentials at low temperature but become harder at higher temperature. Based on the different experimental results obtained, it can be said that various surface, micellar and thermodynamic parameters are dependent not only on the temperature and solution conditions but also on the hydrophobic/hydrophilic ratio and the end-group composition of the polymer. Modification of the hydrophilic end group of the polymer prominently affects various micellar properties. This effect can be assigned to the difference in polarity and the intermicellar charge effect.
Thermochimica Acta, 2014
Abstract The associative, thermodynamic and thermo-kinetics properties of a diblock E 90 B 10 and... more Abstract The associative, thermodynamic and thermo-kinetics properties of a diblock E 90 B 10 and three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type E m B 10 E m water have been studied by surface tensiometry, light scattering and temperature-jump stopped-flow techniques. The data from surface tension was helpful to detect the critical micelle concentration (CMC) as well as to calculate the thermodynamic parameters of micellization. Dynamic light scattering (DLS) was employed to obtain the values of hydrodynamic radii ( R h ), volume ( υ h ) and hydrodynamic expansion parameter ( δ h ) of the micelle at different temperatures. Similarly, static light scattering (SLS) measurements made us enable to find out various micellar parameters such as; weight-average molar ( M w ), association number ( N w ), thermodynamic radius ( R t ), thermodynamic volume ( υ t ), anhydrous volume ( υ a ) and thermodynamic expansion parameter ( δ t ) of the micelles. Likewise, the kinetics of micellar aggregation/dynamic was also investigated by using temperature-jump stopped-flow technique in the temperature range of 20–50 °C.
Chinese Journal of Chemistry, 2014
Journal of Polymer Research, 2014
Journal of Materials Chemistry B, 2014
IOP Conference Series: Materials Science and Engineering, 2014
Journal of Inorganic and Organometallic Polymers and Materials, 2021
Lyophilic microgels based on Gum Acacia (GAC) were synthesized at room temperature and normal pre... more Lyophilic microgels based on Gum Acacia (GAC) were synthesized at room temperature and normal pressure. Briefly, high yield of the spherical shaped microgels of size ≤ 50 µm was obtained via introducing linear GAC and divinyl sulfone (DS) in the reverse micelle cores of NBSS in the stirring gasoline. The GAC microgels were then utilized as synthetic micro-templates for fabricating their nanocomposites with Cobalt (Co), to subsequently produce GAC-Co nanocomposite microgels. The as synthesis GAC based microgels and the GAC-Co microgels were characterized through FTIR, TGA, DSC, SEM, EDS, and TEM. Different amounts of GAC-Co microgels were used as nano-catalyst for the degradation of poisonous aromatic compounds and an Azo dye in aqueous medium. Briefly, 1 g GAC-Co microgels degraded 100 mL (250 ppm solution) of each the aforementioned compounds in ≤ 25 min at neutral pH. The increase in the kinetic parameter i.e., rate constant (kapp) value with increase in the GAC-Co nanocomposite m...
Microscopy Research and Technique
Catalysis Letters
Abstract Hydrogels of Acacia gum (AG) were synthesized in the reverse micelle core of sodium bis ... more Abstract Hydrogels of Acacia gum (AG) were synthesized in the reverse micelle core of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) in gasoline medium. The as synthesized hydrogels were used as template to prepare Silver nanoparticle (AgNPs) in situ via the reduction mechanism of NaBH 4 . The successful synthesis of bare hydrogels and AgNPs loaded nanocomposite hydrogels (AG–Ag hydrogels) were characterized through Fourier Transform Infrared spectroscopy, Thermal gravimetric analysis, Differential Scanning Calorimetry, Scanning Electron Microscopy, energy dispersive X-ray spectroscopy and Transmission Electron Microscopy, and Atomic Absorption Spectroscopy (AAS). Different feeds of the as fabricated GA-Ag hydrogels were used to catalyze the well-known reactions of 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), and Methyl Orange (MO) reduction in aqueous medium at ambient physical conditions. Remarkably, 1000 mg/L of AG–Ag hydrogels with reduced 4-NP and 2-NP into its counterparts, 4-aminophenol and 2-aminophenol in 24 min and 15 min, respectively at room temperature. Similarly, 1000 mg/L of AG–Ag hydrogels reduced MO completely within 25 min. The aforementioned catalytic reactions followed pseudo first order rate kinetics, and it was found that the value of rate constant (kapp) increased by increasing the catalyst amount which, thereby confirms the high conversion rate of the reactants. Graphic Abstract Schematic illustration of fabrication and catalytic action of AgNPs grown inside the pre-synthesized AG Hydrogel matrices.
Iranian Polymer Journal
Well-defined amphiphilic comb-like pentablock copolymers based on Pluronic L64 (PEO13-b-PPO30-b-P... more Well-defined amphiphilic comb-like pentablock copolymers based on Pluronic L64 (PEO13-b-PPO30-b-PEO13) and poly(ethylene glycol)methyl ether methacrylate (PEGMA) have been successfully synthesized via atom transfer radical polymerization (ATRP). The L64 is transformed into ATRP macroinitiator and chain extended with PEGMA under typical ATRP conditions to achieve comb-like pentablock copolymers of various compositions. Due to their amphiphilic nature, the block copolymers could form self-assembled structures in aqueous solutions as confirmed by dynamic light scattering. At higher PEGMA content in the synthesized copolymer, however, the critical aggregation concentration (CAC) is less pronounced that could be attributed to the increased hydrophilicity and steric hindrance of PEG side chains of the PEGMA, thus preventing the formation of well-defined micellar aggregates, and probably leads to open-shell aggregation mechanism. The lower critical solution temperature (LCST) of the synthesized block copolymers is found higher than the neat L64 and increased with increasing the PEGMA content. Further, tuning the clouding behavior could be achieved with inorganic additives (KBr and K2SO4). The influence of SO42− and Br1− on LCST is according to their position in Hofmeister series. Interestingly, the effect of additives is more pronounced above the CAC of the copolymer, suggesting that the nanoaggregates in solution induce the macrophase separation.
Journal of Physics and Chemistry of Solids
Abstract A high charge-carrier transport is an important aim in the synthesis of nanostructures f... more Abstract A high charge-carrier transport is an important aim in the synthesis of nanostructures for an effective supercapacitor. This article describes a methodology to prepare mesoporous silica nanoparticles (MSNs) wrapped with graphene oxide (GO) together with conducting polyaniline (PANI) wires. The morphology and chemical structure of the prepared samples have been tested by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and X-ray diffraction (XRD), whereas the stability and electrostatic interaction of the structures have been verified by thermogravimetric analysis (TGA) and Fourier-transform infrared (FT-IR) spectroscopy, respectively. The supercapacitive behaviour of these nanocomposites has been analysed by cyclic voltammetry (CV), charge–discharge tests, and electrochemical impedance spectroscopy (EIS). Compared with pristine MSNs and PANI, the 20%-GO@MSNs/PANI nanocomposite had the highest specific capacitance, reaching 412 F g−1. The nanocomposite structure maximizes the synergy between mesoporous metal oxide, conducting PANI, and GO, yielding a significantly enhanced specific capacitance, rapid charge–discharge rates, and good cycling stability of the resulting device. The wrapping with GO prevents the structural breakdown and acts as a highly conductive pathway by bridging the individual particles, whereas the MSNs nanoparticles greatly enlarge the specific surface area to facilitate ion transport and charge transfer throughout the cycling performance of supercapacitor. The approach adopted in this article can be applied for preparing similar novel functional materials in future for electrochemical applications.
International Journal of Environmental Science and Technology
This work describes the synthesis of poly(acrylic acid) microgels and fabrication of magnetic cob... more This work describes the synthesis of poly(acrylic acid) microgels and fabrication of magnetic cobalt nanoparticles in the prepared microgels. Cobalt nanoparticles were fabricated by loading the cobalt (II) ions in microgels from aqueous solution and their subsequent reduction with sodium borohydride (NaBH4). Bare and composite microgels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The catalytic properties of the prepared microgel composites were investigated by using them as catalyst for the reduction of 4-nitrophenol and methylene blue. The effect of temperature and catalyst dose on the rate of reduction of these toxic pollutants was investigated. The reusability of prepared catalysts was also studied for the five consecutive cycles, and an increase in catalytic activity was observed after every cycle. The prepared bare and magnetic microgels were found as very effective adsorbent for the removal of methylene blue from aqueous medium. Very rapid adsorption rate was found for the removal of methylene as its 100 mg was adsorbed on per gram of dried hydrogels in about 25 min. The effects of different parameters like amount of adsorbate and concentration of adsorbent on the adsorption process were studied. Langmuir, Freundlich and Temkin adsorption isotherms were applied, and it was found that adsorption of MB follows Freundlich model better than others. Furthermore, pseudo-first-order and pseudo-second-order kinetic models were also applied and adsorption of MB was found to abide by pseudo-second-order kinetics.
New J. Chem., 2017
Active oxygen for CO oxidation over Au/TiO2 is a highly stable atomic species, which is formed at... more Active oxygen for CO oxidation over Au/TiO2 is a highly stable atomic species, which is formed at the perimeter of the Au/oxide interface.
J Appl Polym Sci, 1996
... 1996 SIDDIQ, WU, AND LI ... of gyration and average hydrody-namic radius, respectively, and w... more ... 1996 SIDDIQ, WU, AND LI ... of gyration and average hydrody-namic radius, respectively, and we also determined the calibration between the translational diffusion coefficient D and the molecular weight M for PEK-C in CHC13 at 25°C. We demonstrate that on the basis of our ...
Journal of Polymer Engineering, 2016
Copper nanoparticles (CuNPs) are formed inside a microgel assembly by an
Journal of colloid and interface science, Jan 18, 2016
In this study, the synthesis of micron-sized poly(vinylbenzyl chloride) (p(VBC)) beads and subseq... more In this study, the synthesis of micron-sized poly(vinylbenzyl chloride) (p(VBC)) beads and subsequent conversion of the reactive chloromethyl groups to double amidoxime group containing moieties by post modification is reported. The prepared beads were characterized by SEM and FT-IR spectroscopy. The amidoximated p(VBC) beads were used as adsorbent for the removal of organic dyes, such as eosin y (EY) and methyl orange (MO), and heavy metals containing complex ions such as dichromate (Cr2O7(2-)) and arsenate (HAsO4(2)(-)) from aqueous media. The effect of the adsorbent dose on the percent removal, the effect of initial concentration of adsorbates on the adsorption rate and their amounts were also investigated. The Langmuir, Freundlich and Temkin adsorption isotherms were applied to the adsorption processes. The results indicated that the adsorption of both dichromate and arsenate ions obeyed the Langmuir adsorption model. Interestingly, it was found that the prepared beads were capa...
Encyclopedia of Biomedical Polymers and Polymeric Biomaterials, 2016
Materials Chemistry and Physics, 2016
Abstract The aim of this study is to investigate the kinetics and mechanism of reduction of nitro... more Abstract The aim of this study is to investigate the kinetics and mechanism of reduction of nitrobenzene using novel silver-poly(N-isopropylacrylamide-co-allylacetic acid) hybrid microgels as catalyst. For this purpose effect of catalyst dosage, concentration of nitrobenzene, concentration of sodium borohydride (NaBH 4 ) and temperature on value of apparent rate constant (k app ) was studied. The value of k app linearly increases from 0.083 to 0.313min −1 by increasing catalyst dosage from 66.66 to 102.56 μg/L at 305 K. Initially value of k app increases with increase in concentration of NaBH 4 . After reaching maxima the value of k app decreases with increase in concentration of NaBH 4 . Similar trend in the value of k app was observed in case of nitrobenzene. Retardation in value of k app at very high concentrations of reagents indicates that catalytic reduction obeys Langmuir–Hinshelwood mechanism. k app shows non-linear dependence on temperature. Initially the value of k app increases by increasing temperature upto 308 K due to Arrhenius behavior of reaction. On further increase in temperature upto 312 K the value of k app decreases due to deswelling of hybrid microgels. While the value of k app increases again with increase in temperature above 312 K. Hybrid microgels were characterized by FTIR, DLS, TEM, XRD and UV–Visible spectroscopy.
Journal of Dispersion Science and Technology, 2015
The physicochemical investigations on the associative, micellar, and thermodynamic properties of ... more The physicochemical investigations on the associative, micellar, and thermodynamic properties of a diblock (PEO)62-b-(PBO)33 copolymer in aqueous medium and its interaction with ionic surfactants were carried out by using surface tensiometry, laser light scattering, and steady-state fluorescence spectroscopy. Surface tension and fluorescence measurements were used to find out the critical micelle concentration (CMC) and related thermodynamic parameters of micellization copolymer at various temperatures. The data from dynamic light scattering (DLS) were helpful to obtain the values of hydrodynamic radii (Rh), volume (υh), and hydrodynamic expansion parameter (δh) of the copolymer micelle. Likewise, the measurements from static light scattering (SLS) were employed to determine weight-average molar (Mw), association number (Nw), thermodynamic radius (Rt), thermodynamic volume (υt), anhydrous volume (υa), and thermodynamic expansion parameter (δt) of the copolymer micelles in the temperature range of 20–50°C. Similarly, the interactions between (PEO)62-b-(PBO)33 and two ionic surfactants, sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (CTAB), have also been investigated by fluorescence spectroscopy and DLS at 30°C. Similarly, the interactions between (PEO)62-b-(PBO)33 and two ionic surfactants, sodium dodecyl sulfate and hexadecyl trimethylammonium bromide, have also been investigated by fluorescence spectroscopy and DLS in detail. GRAPHICAL ABSTRACT
Journal of Polymer Research, 2014
This study describes the surface, micellar, associative and thermodynamic properties of four dibl... more This study describes the surface, micellar, associative and thermodynamic properties of four diblock oxyethylene (E)/oxybutylene (B) copolymers with different hydrophilic block ends and various hydrophilic/hydrophobic ratios in aqueous media. The copolymers were denoted DE 40 B 18 , TE 40 B 18 , E 56 B 19 and E 56 B 7. The aqueous polymer solutions at various concentrations and temperatures were investigated by surface tensiometry and dynamic and static laser light scattering. Surface tension measurements were employed to detect the critical micelle concentration (CMC) as well as to calculate the surface-active and thermodynamic parameters of adsorption at the air/water interface. CMC values were also used to calculate the enthalpy of micellization (ΔH 0 mic), free energy of micellization (ΔG 0 mic) and entropy of micellization (ΔS 0 mic). Similarly, various thermodynamic parameters for adsorption at the air/water interface were also deduced. Dynamic light scattering (DLS) was used to obtain the hydrodynamic radii (r h) and volumes (υ h) of the micelle at different temperatures, and hence the hydrodynamic expansion parameter (δ h) was also estimated. Likewise, static light-scattering measurements enabled us to determine various parameters of the copolymer micelles, such as the weightaverage molar mass (M w), association number (N w), thermodynamic radius (r t), thermodynamic volume (υ t), anhydrous volume (υ a) and the thermodynamic expansion parameter (δ t). Various thermodynamic and micellar parameters obtained from light scattering show that the micelles formed are spherical in shape and have rather soft interaction potentials at low temperature but become harder at higher temperature. Based on the different experimental results obtained, it can be said that various surface, micellar and thermodynamic parameters are dependent not only on the temperature and solution conditions but also on the hydrophobic/hydrophilic ratio and the end-group composition of the polymer. Modification of the hydrophilic end group of the polymer prominently affects various micellar properties. This effect can be assigned to the difference in polarity and the intermicellar charge effect.
Thermochimica Acta, 2014
Abstract The associative, thermodynamic and thermo-kinetics properties of a diblock E 90 B 10 and... more Abstract The associative, thermodynamic and thermo-kinetics properties of a diblock E 90 B 10 and three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type E m B 10 E m water have been studied by surface tensiometry, light scattering and temperature-jump stopped-flow techniques. The data from surface tension was helpful to detect the critical micelle concentration (CMC) as well as to calculate the thermodynamic parameters of micellization. Dynamic light scattering (DLS) was employed to obtain the values of hydrodynamic radii ( R h ), volume ( υ h ) and hydrodynamic expansion parameter ( δ h ) of the micelle at different temperatures. Similarly, static light scattering (SLS) measurements made us enable to find out various micellar parameters such as; weight-average molar ( M w ), association number ( N w ), thermodynamic radius ( R t ), thermodynamic volume ( υ t ), anhydrous volume ( υ a ) and thermodynamic expansion parameter ( δ t ) of the micelles. Likewise, the kinetics of micellar aggregation/dynamic was also investigated by using temperature-jump stopped-flow technique in the temperature range of 20–50 °C.
Chinese Journal of Chemistry, 2014
Journal of Polymer Research, 2014
Journal of Materials Chemistry B, 2014
IOP Conference Series: Materials Science and Engineering, 2014