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Sangram K. Rath - One of the best experts on this subject based on the ideXlab platform.
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effect of constrained Amorphous Region on properties of acid base polyelectrolyte membranes based on sulphonated poly ether ether ketone and a nonconjugated diamine
Journal of Membrane Science, 2016Co-Authors: Varsha R. Hande, Sangram K. Rath, Swati Rao, S. Praveen, Savita Sasane, Manoranjan PatriAbstract:Abstract The phenomenon of polymer chains being restrained from participating in relaxation mechanisms has been discussed for a number of situations in the field of polymer science. In the present study we invoke the same as a mechanistic origin of property improvement in an acid–base polymeric membrane for fuel cell application. Sulfonated polyether ether ketone (sPEEK) and a non conjugated diamine (3, 3′ dichloro 4,4′ diaminodiphenylmethane) were used as the acid and base components, respectively to prepare the membranes by a facile solvent casting process. The ionic cross-link induced constrained Amorphous Region (C) in the acid–base membranes is quantified as a function of basic component loading from the relative depression in the dissipation factor, tan δ using dynamic mechanical analysis (DMA); found to be a staggering 62% at 25% basic component loading. The significantly higher C values are attributed to strong acid–base interactions as established from morphological investigations by field emission scanning electron microscopy (FESEM), FTIR studies and IEC measurements. Consequent to the existence of constrained Amorphous Region of reduced mobility, significant improvement in thermomechanical properties, (~5 fold increase in storage modulus, 2 fold increase in tensile strength and ~100 °C increase in glass transition temperature compared to pristine sPEEK) thermal, dimensional as well as oxidative stability, of the acid–base membranes are observed compared to the pristine SPEEK membrane. We envisage that the hitherto unexplored acid–base membranes derived from an acidic polymer and a small molecule non-conjugated diamine can also be suitable candidates for fuel cell applications. In addition these fundamental studies are expected to provide insights into mechanistic origins of the property improvements in acid–base membranes.
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characterizing the nanoclay induced constrained Amorphous Region in model segmented polyurethane urea clay nanocomposites and its implications on gas barrier properties
Physical Chemistry Chemical Physics, 2016Co-Authors: Sangram K. Rath, Kathi Sudarshan, Rupesh S. Bhavsar, Ulhas K. Kharul, Pradeep K. Pujari, M. Patri, Devang V. KhakharAbstract:There has been an increasing recognition of the fact that purely geometric factors associated with clay platelet dispersion in a polymer matrix cannot adequately explain the barrier properties of polymer/clay nanocomposites. The objective of the present work is to understand the nanoclay induced structural changes in a polyurethane-urea matrix and clay dispersion at different length scales using segment-specific characterization techniques and implications of the same in gas barrier properties using He, N2 and CO2 as probe molecules. Wide angle X-ray diffraction (WAXD) and positron annihilation life time spectroscopy (PALS) studies revealed nanoclay induced alterations in the chain packing of the Amorphous soft segments of the polyurethane matrix at a molecular scale of a few Angstroms. The hard segment organization and the phase morphology of the nanocomposites, spanning length scales of several nanometers, were investigated by small angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, the presence of a constrained Amorphous Region surrounding the nanoclay was confirmed from AFM, WAXD and PALS results. Several pertinent structural variables from the gas transport point of view were deduced from these characterization techniques to understand the effect of the barrier properties in tandem with the clay dispersion morphology.
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Effect of constrained Amorphous Region on properties of acid–base polyelectrolyte membranes based on sulphonated poly(ether ether ketone) and a nonconjugated diamine
Journal of Membrane Science, 2016Co-Authors: Varsha R. Hande, Sangram K. Rath, Swati Rao, S. Praveen, Savita Sasane, Manoranjan PatriAbstract:Abstract The phenomenon of polymer chains being restrained from participating in relaxation mechanisms has been discussed for a number of situations in the field of polymer science. In the present study we invoke the same as a mechanistic origin of property improvement in an acid–base polymeric membrane for fuel cell application. Sulfonated polyether ether ketone (sPEEK) and a non conjugated diamine (3, 3′ dichloro 4,4′ diaminodiphenylmethane) were used as the acid and base components, respectively to prepare the membranes by a facile solvent casting process. The ionic cross-link induced constrained Amorphous Region (C) in the acid–base membranes is quantified as a function of basic component loading from the relative depression in the dissipation factor, tan δ using dynamic mechanical analysis (DMA); found to be a staggering 62% at 25% basic component loading. The significantly higher C values are attributed to strong acid–base interactions as established from morphological investigations by field emission scanning electron microscopy (FESEM), FTIR studies and IEC measurements. Consequent to the existence of constrained Amorphous Region of reduced mobility, significant improvement in thermomechanical properties, (~5 fold increase in storage modulus, 2 fold increase in tensile strength and ~100 °C increase in glass transition temperature compared to pristine sPEEK) thermal, dimensional as well as oxidative stability, of the acid–base membranes are observed compared to the pristine SPEEK membrane. We envisage that the hitherto unexplored acid–base membranes derived from an acidic polymer and a small molecule non-conjugated diamine can also be suitable candidates for fuel cell applications. In addition these fundamental studies are expected to provide insights into mechanistic origins of the property improvements in acid–base membranes.
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Characterizing the nanoclay induced constrained Amorphous Region in model segmented polyurethane-urea/clay nanocomposites and its implications on gas barrier properties.
Physical Chemistry Chemical Physics, 2015Co-Authors: Sangram K. Rath, Kathi Sudarshan, Rupesh S. Bhavsar, Ulhas K. Kharul, Pradeep K. Pujari, M. Patri, Devang V. KhakharAbstract:There has been an increasing recognition of the fact that purely geometric factors associated with clay platelet dispersion in a polymer matrix cannot adequately explain the barrier properties of polymer/clay nanocomposites. The objective of the present work is to understand the nanoclay induced structural changes in a polyurethane-urea matrix and clay dispersion at different length scales using segment-specific characterization techniques and implications of the same in gas barrier properties using He, N2 and CO2 as probe molecules. Wide angle X-ray diffraction (WAXD) and positron annihilation life time spectroscopy (PALS) studies revealed nanoclay induced alterations in the chain packing of the Amorphous soft segments of the polyurethane matrix at a molecular scale of a few Angstroms. The hard segment organization and the phase morphology of the nanocomposites, spanning length scales of several nanometers, were investigated by small angle X-ray scattering (SAXS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Furthermore, the presence of a constrained Amorphous Region surrounding the nanoclay was confirmed from AFM, WAXD and PALS results. Several pertinent structural variables from the gas transport point of view were deduced from these characterization techniques to understand the effect of the barrier properties in tandem with the clay dispersion morphology.
Manoranjan Patri - One of the best experts on this subject based on the ideXlab platform.
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effect of constrained Amorphous Region on properties of acid base polyelectrolyte membranes based on sulphonated poly ether ether ketone and a nonconjugated diamine
Journal of Membrane Science, 2016Co-Authors: Varsha R. Hande, Sangram K. Rath, Swati Rao, S. Praveen, Savita Sasane, Manoranjan PatriAbstract:Abstract The phenomenon of polymer chains being restrained from participating in relaxation mechanisms has been discussed for a number of situations in the field of polymer science. In the present study we invoke the same as a mechanistic origin of property improvement in an acid–base polymeric membrane for fuel cell application. Sulfonated polyether ether ketone (sPEEK) and a non conjugated diamine (3, 3′ dichloro 4,4′ diaminodiphenylmethane) were used as the acid and base components, respectively to prepare the membranes by a facile solvent casting process. The ionic cross-link induced constrained Amorphous Region (C) in the acid–base membranes is quantified as a function of basic component loading from the relative depression in the dissipation factor, tan δ using dynamic mechanical analysis (DMA); found to be a staggering 62% at 25% basic component loading. The significantly higher C values are attributed to strong acid–base interactions as established from morphological investigations by field emission scanning electron microscopy (FESEM), FTIR studies and IEC measurements. Consequent to the existence of constrained Amorphous Region of reduced mobility, significant improvement in thermomechanical properties, (~5 fold increase in storage modulus, 2 fold increase in tensile strength and ~100 °C increase in glass transition temperature compared to pristine sPEEK) thermal, dimensional as well as oxidative stability, of the acid–base membranes are observed compared to the pristine SPEEK membrane. We envisage that the hitherto unexplored acid–base membranes derived from an acidic polymer and a small molecule non-conjugated diamine can also be suitable candidates for fuel cell applications. In addition these fundamental studies are expected to provide insights into mechanistic origins of the property improvements in acid–base membranes.
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Effect of constrained Amorphous Region on properties of acid–base polyelectrolyte membranes based on sulphonated poly(ether ether ketone) and a nonconjugated diamine
Journal of Membrane Science, 2016Co-Authors: Varsha R. Hande, Sangram K. Rath, Swati Rao, S. Praveen, Savita Sasane, Manoranjan PatriAbstract:Abstract The phenomenon of polymer chains being restrained from participating in relaxation mechanisms has been discussed for a number of situations in the field of polymer science. In the present study we invoke the same as a mechanistic origin of property improvement in an acid–base polymeric membrane for fuel cell application. Sulfonated polyether ether ketone (sPEEK) and a non conjugated diamine (3, 3′ dichloro 4,4′ diaminodiphenylmethane) were used as the acid and base components, respectively to prepare the membranes by a facile solvent casting process. The ionic cross-link induced constrained Amorphous Region (C) in the acid–base membranes is quantified as a function of basic component loading from the relative depression in the dissipation factor, tan δ using dynamic mechanical analysis (DMA); found to be a staggering 62% at 25% basic component loading. The significantly higher C values are attributed to strong acid–base interactions as established from morphological investigations by field emission scanning electron microscopy (FESEM), FTIR studies and IEC measurements. Consequent to the existence of constrained Amorphous Region of reduced mobility, significant improvement in thermomechanical properties, (~5 fold increase in storage modulus, 2 fold increase in tensile strength and ~100 °C increase in glass transition temperature compared to pristine sPEEK) thermal, dimensional as well as oxidative stability, of the acid–base membranes are observed compared to the pristine SPEEK membrane. We envisage that the hitherto unexplored acid–base membranes derived from an acidic polymer and a small molecule non-conjugated diamine can also be suitable candidates for fuel cell applications. In addition these fundamental studies are expected to provide insights into mechanistic origins of the property improvements in acid–base membranes.
Louis N. Howard - One of the best experts on this subject based on the ideXlab platform.
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Loop Entanglement of Semicrystalline Polyethylene in Amorphous Region: Diamond Lattice Approach
Journal of Computational Chemistry, 1999Co-Authors: Zhong-hui Duan, Louis N. HowardAbstract:Linear polyethylenes in the Amorphous Region have been simulated as restricted random walks on a diamond lattice between two absorbing planes. The links among loops were studied by treating loops as oriented curves. The local conformations of polyethylene chains i.e., trans and . gauche energy differences were considered in the simulation, thereby determining the effect of crystallization temperature on the loop entanglement. It was found that the total Gauss winding and link density of linked loops increased with the thickness of the Amorphous Region. This result agrees with that of the cubic lattice model. The link probability decreases very slowly with the thickness of the Amorphous Region. On the other hand, the results presented clearly indicate that all statistical measures of linked loops decrease with temperature. Q 1999 John Wiley & Sons, Inc. J Comput Chem 20: 348)353, 1999
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Diamond lattice model of semicrystalline polyethylene in the Amorphous Region
The Journal of Chemical Physics, 1998Co-Authors: Zhong-hui Duan, Louis N. HowardAbstract:The statistics of polyethylene chains in the Amorphous Region between two crystallites have been computed, modeling the chains as random walks on a diamond lattice with two absorbing boundaries. The probabilities of trans and gauche states are considered, thereby determining some effects of temperature, e.g. at higher temperature more loops are formed and the average length of loops is shorter, in contrast to less ties formed with a longer average length. It is found that the lower bound on the adjacent reentry is 79% at very high temperature and it increases to 81% at about 400 K.
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A modified gambler's ruin model of polyethylene chains in the Amorphous Region.
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: Zhong-hui Duan, Louis N. HowardAbstract:Abstract Polyethylene chains in the Amorphous Region between two crystalline lamellae M unit apart are modeled as random walks with one-step memory on a cubic lattice between two absorbing boundaries. These walks avoid the two preceding steps, though they are not true self-avoiding walks. Systems of difference equations are introduced to calculate the statistics of the restricted random walks. They yield that the fraction of loops is (2M - 2)/(2M + 1), the fraction of ties 3/(2M + 1), the average length of loops 2M - 0.5, the average length of ties 2/3M2 + 2/3M - 4/3, the average length of walks equals 3M - 3, the variance of the loop length 16/15M3 + O(M2), the variance of the tie length 28/45M4 + O(M3), and the variance of the walk length 2M3 + O(M2).
Koji Sumino - One of the best experts on this subject based on the ideXlab platform.
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Stress-induced amorphization of silicon crystal by mechanical scratching.
Physical review letters, 1992Co-Authors: Kyoko Minowa, Koji SuminoAbstract:The damaged layer induced in a silicon crystal by surface scratching at room temperature under a light load was found, by transmission electron microscopy, to be a small Amorphous Region surrounded by a dislocated crystalline Region. No dent was detected on the surface and no crack was developed around the scratch. The Amorphous Region seems to be formed by phase transformation and not as the result of heavy plastic deformation of the crystal. The Amorphous Region was recrystallized to a dislocated crystalline Region by annealing of the crystal at 600 \ifmmode^\circ\else\textdegree\fi{}C.
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Stress-induced amorphization of silicon crystal by mechanical scratching.
Physical review letters, 1992Co-Authors: Kyoko Minowa, Koji SuminoAbstract:The damaged layer induced in a silicon crystal by surface scratching at room temperature under a light load was found, by transmission electron miocroscopy, to be a small Amorphous Region surrounded by a dislocated crystalline Region. No dent was detected on the surface and no crack was developed around the scratch. The Amorphous Region seems to be formed by phase transformation and not as the result of heavy plastic deformation of the crytal
Varsha R. Hande - One of the best experts on this subject based on the ideXlab platform.
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effect of constrained Amorphous Region on properties of acid base polyelectrolyte membranes based on sulphonated poly ether ether ketone and a nonconjugated diamine
Journal of Membrane Science, 2016Co-Authors: Varsha R. Hande, Sangram K. Rath, Swati Rao, S. Praveen, Savita Sasane, Manoranjan PatriAbstract:Abstract The phenomenon of polymer chains being restrained from participating in relaxation mechanisms has been discussed for a number of situations in the field of polymer science. In the present study we invoke the same as a mechanistic origin of property improvement in an acid–base polymeric membrane for fuel cell application. Sulfonated polyether ether ketone (sPEEK) and a non conjugated diamine (3, 3′ dichloro 4,4′ diaminodiphenylmethane) were used as the acid and base components, respectively to prepare the membranes by a facile solvent casting process. The ionic cross-link induced constrained Amorphous Region (C) in the acid–base membranes is quantified as a function of basic component loading from the relative depression in the dissipation factor, tan δ using dynamic mechanical analysis (DMA); found to be a staggering 62% at 25% basic component loading. The significantly higher C values are attributed to strong acid–base interactions as established from morphological investigations by field emission scanning electron microscopy (FESEM), FTIR studies and IEC measurements. Consequent to the existence of constrained Amorphous Region of reduced mobility, significant improvement in thermomechanical properties, (~5 fold increase in storage modulus, 2 fold increase in tensile strength and ~100 °C increase in glass transition temperature compared to pristine sPEEK) thermal, dimensional as well as oxidative stability, of the acid–base membranes are observed compared to the pristine SPEEK membrane. We envisage that the hitherto unexplored acid–base membranes derived from an acidic polymer and a small molecule non-conjugated diamine can also be suitable candidates for fuel cell applications. In addition these fundamental studies are expected to provide insights into mechanistic origins of the property improvements in acid–base membranes.
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Effect of constrained Amorphous Region on properties of acid–base polyelectrolyte membranes based on sulphonated poly(ether ether ketone) and a nonconjugated diamine
Journal of Membrane Science, 2016Co-Authors: Varsha R. Hande, Sangram K. Rath, Swati Rao, S. Praveen, Savita Sasane, Manoranjan PatriAbstract:Abstract The phenomenon of polymer chains being restrained from participating in relaxation mechanisms has been discussed for a number of situations in the field of polymer science. In the present study we invoke the same as a mechanistic origin of property improvement in an acid–base polymeric membrane for fuel cell application. Sulfonated polyether ether ketone (sPEEK) and a non conjugated diamine (3, 3′ dichloro 4,4′ diaminodiphenylmethane) were used as the acid and base components, respectively to prepare the membranes by a facile solvent casting process. The ionic cross-link induced constrained Amorphous Region (C) in the acid–base membranes is quantified as a function of basic component loading from the relative depression in the dissipation factor, tan δ using dynamic mechanical analysis (DMA); found to be a staggering 62% at 25% basic component loading. The significantly higher C values are attributed to strong acid–base interactions as established from morphological investigations by field emission scanning electron microscopy (FESEM), FTIR studies and IEC measurements. Consequent to the existence of constrained Amorphous Region of reduced mobility, significant improvement in thermomechanical properties, (~5 fold increase in storage modulus, 2 fold increase in tensile strength and ~100 °C increase in glass transition temperature compared to pristine sPEEK) thermal, dimensional as well as oxidative stability, of the acid–base membranes are observed compared to the pristine SPEEK membrane. We envisage that the hitherto unexplored acid–base membranes derived from an acidic polymer and a small molecule non-conjugated diamine can also be suitable candidates for fuel cell applications. In addition these fundamental studies are expected to provide insights into mechanistic origins of the property improvements in acid–base membranes.