Mohammed Sharaf - Academia.edu (original) (raw)
Papers by Mohammed Sharaf
International Journal of Nano and Biomaterials, 2009
Int. J. Nano and Biomaterials, Vol. 2, Nos. 1/2/3/4/5, 2009 ... Effects of deformation and physic... more Int. J. Nano and Biomaterials, Vol. 2, Nos. 1/2/3/4/5, 2009 ... Effects of deformation and physical aging on nano-scale free volumes in polycarbonate studied by positron annihilation lifetime spectroscopy ... Physics Department, Faculty of Science, A in Shams University, Abbassia 11566, ...
Colloid & Polymer Science, 1994
... The mean positions of the junc-tions are affine in the strain, but the fluctuations about the... more ... The mean positions of the junc-tions are affine in the strain, but the fluctuations about the mean positions are invariant with strain. The modulus is given by [8-10, 8-22] [f*]ph ~ RT02/3 = 2c , (3) where [18-22] = v,- #a = v-# (4) ...
Polymer Engineering and Science, 1986
Networks were prepared from a sample of 1,4-polybutacliene having an extremely high cis content (... more Networks were prepared from a sample of 1,4-polybutacliene having an extremely high cis content (98.5 mol percent) and from other samples having relatively high trans contents (72 to 80 mol percent). The cross-linking techniques employed were gamma irradiation, ultraviolet irradiation, and peroxide thermolysis. The resulting elastomers were studied in elongation in the unswollen state at several temperatures, to their rupture points, and in swelling equilibrium in a good solvent. Values of the elasticity constant 2C1 obtained from the stress-strain isotherms at low and moderate elongations gave values of the molecular weight M, between cross-links in at least approximate agreement with those obtained from the swelling equilibrium data. The other elasticity constant 2C2 generally had relatively large values, suggesting inhomogeneous cross-linking, but approached zero for small Mc as expected from reduced configurational interpenetration. At high elongations, the reduced stress for the high-cis polymer showed marked upturns due to strain-induced crystallization.
... The networks formed by end-linking relatively short chains have small values of the semiempir... more ... The networks formed by end-linking relatively short chains have small values of the semiempirical constant 2 C2 used as a measure of the departure of an observed stress-strain isotherm from the form predicted by theory. Although ...
Journal of Polymer Science Part B: Polymer Physics, 1995
Several groups have now prepared poly(dimethylsi1oxane) networks of high cross-link functionality... more Several groups have now prepared poly(dimethylsi1oxane) networks of high cross-link functionality by end-linking vinyl-terminated chains by means of Si-H groups in siloxane oligomers (CH3)3SiO[SiHCH30],Si(CH,)3. The elongation moduli of these networks were generally found to be considerably larger than the values predicted from the functionality and number density of the cross links (based on the stoichiometry of the end-linking reaction). Not all the Si-H groups in an oligomer are used in the end-linking reaction, however, and the segments between cross-links can themselves act as short network chains. The connectivity of these short chains to the long ones, in what is essentially a bimodal distribution, has been neglected in analyses to date. They are taken into account in the present analysis, giving much better agreement between experiment and theory. The stress-strain behavior for such very short chains can be characterized by the use of Monte Carlo methods and the Fixman-Alben non-Gaussian distribution. This alternative analysis seems useful in reproducing the experimental observations, but further experimental and theoretical will be required to remove some remaining ambiguities.
Polymer
Although the ®ller particles typically used to reinforce elastomers are at least approximately sp... more Although the ®ller particles typically used to reinforce elastomers are at least approximately spherical, prolate (needle-shaped) or oblate (disc-shaped) particles have been used in some cases. The fact that anisotropic structures and properties can be obtained in these cases has encouraged a number of experimental and theoretical investigations. The present study extends some earlier Monte Carlo simulations on prolate particles in an amorphous polyethylene matrix, but now focuses on oblate particles. The particles were placed on a cubic lattice, and were oriented in a way consistent with their orientation in composites that were the subject of an experimental investigation by one of the authors. Rotational isomeric state representations of the chains were then generated to model the elastomeric network in the presence of the ®ller particles. The chain end-to-end distributions were found to be non-Gaussian, and to depend signi®cantly on the excluded volumes of the particles. The particle-induced deformations of the network chains were consistent with results of some other relevant simulations and with recent neutron scattering results. Speci®cally, the chain dimensions were found to decrease with increase in the axial ratios characterizing the oblate shapes. As anticipated, the chain dimensions became anisotropic, with signi®cant differences parallel and perpendicular to the direction of the particle axes. In general, the network chains tended to adopt more compressed con®gurations relative to those of prolate particles having equivalent sizes and aspect ratios. Use of these distributions in a standard molecular model for rubberlike elasticity gave values of the elongation moduli, and these were found to depend on the sizes, number, and axial ratios of the particles, as expected. In particular, the reinforcement from the oblate particles was found to be greatest in the plane of the particles, and the changes were in at least qualitative agreement with the corresponding experimental results.
Polymer, 2004
Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler parti... more Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler particles arranged either on a cubic lattice or randomly in space. Attention was first focused on the effects of the type of arrangement of the particles on the microscopic properties of the polymer chains. Specifically, Monte Carlo rotational isomeric state (MC-RIS) simulations were carried out to predict the effects of the volumes excluded by the filler particles on the configurational distribution functions of the chains, and from these distributions the elastomeric properties of the composites. The calculations were carried out for a range of particle sizes and particle volume fractions. As expected, filler inclusions are found to increase the non-Gaussian behavior of the chains. The results were compared with those from smallangle neutron scattering (SANS) experiments. In the case of arrangement on a cubic lattice, chains dimensions were always found to decrease. In the randomly-dispersed filler arrangements, there were significant increases in chain dimensions relative to the unfilled system in some instances, and the changes were in excellent agreement with the SANS results. The present simulations thus give further encouragement to interpretations of chain deformations in filled systems in terms of volume exclusion effects from the nanoparticle inclusions, including their dispersions and arrangements within polymer matrices.
Macromolecules, 2004
ABSTRACT
Journal of Macromolecular Science Part a, 2004
ABSTRACT
Nature and Science of Sleep, 2011
Collidally stabilized gold nanoparticles NPs having sizes in the range of 3-20 nm have been prepa... more Collidally stabilized gold nanoparticles NPs having sizes in the range of 3-20 nm have been prepared by citrate chemical reduction methods. The gold nanoparticles were characterized employing transmission electron microscopy TEM. The in vitro release kinetics and associated antifungal effects were investigated for Pencillium. Micro plate reader analyses were utilized for monitoring the antifungal effects. The results provided strong evidence that could warrant the consideration of gold nanoparticles as antifungal material. Such treatment could circumvent the side and passive immune effects of other antifungal material. Also, the nanoparticles thus prepared have the potential and ability of targeting specific sites.
Polymer, 2005
The elastomeric properties of networks of stereoregular polypropylenes (PP) filled with spherical... more The elastomeric properties of networks of stereoregular polypropylenes (PP) filled with spherical nanoparticles have been modeled in an attempt to obtain better insights into elastomer reinforcement. The polymers were either isotactic or syndiotactic PP in the ...
International Journal of Nanomedicine, 2011
Background: Nanosized dry powder inhalers provide higher stability for poorly water-soluble drugs... more Background: Nanosized dry powder inhalers provide higher stability for poorly water-soluble drugs as compared with liquid formulations. However, the respirable particles must have a diameter of 1-5 µm in order to deposit in the lungs. Controlled agglomeration of the nanoparticles increases their geometric particle size so they can deposit easily in the lungs. In the lungs, they fall apart to reform nanoparticles, thus enhancing the dissolution rate of the drugs. Theophylline is a bronchodilator with poor solubility in water. Methods: Nanosized theophylline colloids were formed using an amphiphilic surfactant and destabilized using dilute sodium chloride solutions to form the agglomerates. Results: The theophylline nanoparticles thus obtained had an average particle size of 290 nm and a zeta potential of −39.5 mV, whereas the agglomerates were 2.47 µm in size with a zeta potential of −28.9 mV. The release profile was found to follow first-order kinetics (r 2. 0.96). The aerodynamic characteristics of the agglomerated nanoparticles were determined using a cascade impactor. The behavior of the agglomerate was significantly better than unprocessed raw theophylline powder. In addition, the nanoparticles and agglomerates resulted in a significant improvement in the dissolution of theophylline. Conclusion: The results obtained lend support to the hypothesis that controlled agglomeration strategies provide an efficient approach for the delivery of poorly water-soluble drugs into the lungs.
Polymer, 2004
Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler parti... more Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler particles arranged either on a cubic lattice or randomly in space. Attention was first focused on the effects of the type of arrangement of the particles on the microscopic properties of the polymer chains. Specifically, Monte Carlo rotational isomeric state (MC-RIS) simulations were carried out to predict the effects of the volumes excluded by the filler particles on the configurational distribution functions of the chains, and from these distributions the elastomeric properties of the composites. The calculations were carried out for a range of particle sizes and particle volume fractions. As expected, filler inclusions are found to increase the non-Gaussian behavior of the chains. The results were compared with those from smallangle neutron scattering (SANS) experiments. In the case of arrangement on a cubic lattice, chains dimensions were always found to decrease. In the randomly-dispersed filler arrangements, there were significant increases in chain dimensions relative to the unfilled system in some instances, and the changes were in excellent agreement with the SANS results. The present simulations thus give further encouragement to interpretations of chain deformations in filled systems in terms of volume exclusion effects from the nanoparticle inclusions, including their dispersions and arrangements within polymer matrices.
Polymer, 2005
We derived the analytical solution of the eigenvalue problem for stereo-regular vinyl chains, suc... more We derived the analytical solution of the eigenvalue problem for stereo-regular vinyl chains, such as stereo-regular polypropylene chains. The solution is applicable to all stereo-regular polymers of the type (AB)x which do not have symmetry between gauche+ and gauche− states, and to polymers, such as polyoxymethylene or polydimethylsiloxane, for which symmetry between the gauche+ and gauche− states does exist. For symmetric chains, the general solution of the eigenvalue problem is reduced to the known solution for polyoxymethylene chains. To illustrate the method the calculations have been performed for the three rotational states (trans, gauche+ and gauche−) model, but the general algebraic solution is applicable for any ν rotational states models of polymer chains. We used the analytical solution of the eigenvalue problem to calculate numerically elastic properties of stereo-regular polypropylene chains within the framework of Mark–Curro theory (J Chem Phys, 79, 5705, 1983).
Materials Science and Engineering: A, 2005
A review of the recent work on polymer matrix nanocomposites is presented. This review is not int... more A review of the recent work on polymer matrix nanocomposites is presented. This review is not intended to be comprehensive, but provides an overview of the processing techniques and trends in the mechanical behavior and morphology of nanocomposites. A number of composite systems with amorphous and/or crystalline polymer matrices and different nano-sized filler materials are discussed.
Macromolecules, 2004
ABSTRACT
Journal of Polymer Science Part B: Polymer Physics, 1996
computer simulations were carried out on filled networks of poly(dimethylsiloxane) (PDMS), which ... more computer simulations were carried out on filled networks of poly(dimethylsiloxane) (PDMS), which were modeled as composites of crosslinked chains and randomly arranged spherical filler particles. The primary concern of the investigation was the effect of the excluded volume of these particles on the elastomeric properties of the polymers. Calculations were carried out for PDMS chains with different molecular masses between crosslinks, and for filler particles with different sizes and a t various volume percentages. Distributions of end-to-end vectors for both unfilled and filled networks were obtained using Monte Carlo simulations based on rotational isomeric state (RIS) theory. More extended configurations, with a higher end-to-end distance, were observed for networks filled with smaller particles. The nominal stress f * and the modulus or reduced nominal stress [f*] were calculated from the distributions of end-to-end vectors using the Mark-Curro approach. Relatively small filler particles were found to increase the non-Gaussian behavior and to increase the normalized moduli above the reference value of unity. Temperature effects on the stress were also investigated.
European Polymer Journal, 2006
Monte Carlo simulations based on rotational isomeric state models were carried out to determine h... more Monte Carlo simulations based on rotational isomeric state models were carried out to determine how amorphous polyethylene chains are deformed by the presence of spherical filler particles. The resulting distributions of the chain end-to-end distances were then employed to calculate mechanical properties of the cross-linked chains. The basic goals were (i) to refine previous simulations of this type carried out on this system to remove possible sampling biases, and (ii) to document the circumstances under which the particles stretch the chains to larger end-to-end distances, rather than compress them to smaller distances, and (iii) to study in more detail the flattening of the chains near particle surfaces. Comparisons with experiments include filler-induced changes in chain dimensions measured by neutron scattering, and general features of the stress-strain isotherms widely observed for reinforced elastomers in simple elongation.
Colloid and Polymer Science, 2006
International Journal of Nano and Biomaterials, 2009
Int. J. Nano and Biomaterials, Vol. 2, Nos. 1/2/3/4/5, 2009 ... Effects of deformation and physic... more Int. J. Nano and Biomaterials, Vol. 2, Nos. 1/2/3/4/5, 2009 ... Effects of deformation and physical aging on nano-scale free volumes in polycarbonate studied by positron annihilation lifetime spectroscopy ... Physics Department, Faculty of Science, A in Shams University, Abbassia 11566, ...
Colloid & Polymer Science, 1994
... The mean positions of the junc-tions are affine in the strain, but the fluctuations about the... more ... The mean positions of the junc-tions are affine in the strain, but the fluctuations about the mean positions are invariant with strain. The modulus is given by [8-10, 8-22] [f*]ph ~ RT02/3 = 2c , (3) where [18-22] = v,- #a = v-# (4) ...
Polymer Engineering and Science, 1986
Networks were prepared from a sample of 1,4-polybutacliene having an extremely high cis content (... more Networks were prepared from a sample of 1,4-polybutacliene having an extremely high cis content (98.5 mol percent) and from other samples having relatively high trans contents (72 to 80 mol percent). The cross-linking techniques employed were gamma irradiation, ultraviolet irradiation, and peroxide thermolysis. The resulting elastomers were studied in elongation in the unswollen state at several temperatures, to their rupture points, and in swelling equilibrium in a good solvent. Values of the elasticity constant 2C1 obtained from the stress-strain isotherms at low and moderate elongations gave values of the molecular weight M, between cross-links in at least approximate agreement with those obtained from the swelling equilibrium data. The other elasticity constant 2C2 generally had relatively large values, suggesting inhomogeneous cross-linking, but approached zero for small Mc as expected from reduced configurational interpenetration. At high elongations, the reduced stress for the high-cis polymer showed marked upturns due to strain-induced crystallization.
... The networks formed by end-linking relatively short chains have small values of the semiempir... more ... The networks formed by end-linking relatively short chains have small values of the semiempirical constant 2 C2 used as a measure of the departure of an observed stress-strain isotherm from the form predicted by theory. Although ...
Journal of Polymer Science Part B: Polymer Physics, 1995
Several groups have now prepared poly(dimethylsi1oxane) networks of high cross-link functionality... more Several groups have now prepared poly(dimethylsi1oxane) networks of high cross-link functionality by end-linking vinyl-terminated chains by means of Si-H groups in siloxane oligomers (CH3)3SiO[SiHCH30],Si(CH,)3. The elongation moduli of these networks were generally found to be considerably larger than the values predicted from the functionality and number density of the cross links (based on the stoichiometry of the end-linking reaction). Not all the Si-H groups in an oligomer are used in the end-linking reaction, however, and the segments between cross-links can themselves act as short network chains. The connectivity of these short chains to the long ones, in what is essentially a bimodal distribution, has been neglected in analyses to date. They are taken into account in the present analysis, giving much better agreement between experiment and theory. The stress-strain behavior for such very short chains can be characterized by the use of Monte Carlo methods and the Fixman-Alben non-Gaussian distribution. This alternative analysis seems useful in reproducing the experimental observations, but further experimental and theoretical will be required to remove some remaining ambiguities.
Polymer
Although the ®ller particles typically used to reinforce elastomers are at least approximately sp... more Although the ®ller particles typically used to reinforce elastomers are at least approximately spherical, prolate (needle-shaped) or oblate (disc-shaped) particles have been used in some cases. The fact that anisotropic structures and properties can be obtained in these cases has encouraged a number of experimental and theoretical investigations. The present study extends some earlier Monte Carlo simulations on prolate particles in an amorphous polyethylene matrix, but now focuses on oblate particles. The particles were placed on a cubic lattice, and were oriented in a way consistent with their orientation in composites that were the subject of an experimental investigation by one of the authors. Rotational isomeric state representations of the chains were then generated to model the elastomeric network in the presence of the ®ller particles. The chain end-to-end distributions were found to be non-Gaussian, and to depend signi®cantly on the excluded volumes of the particles. The particle-induced deformations of the network chains were consistent with results of some other relevant simulations and with recent neutron scattering results. Speci®cally, the chain dimensions were found to decrease with increase in the axial ratios characterizing the oblate shapes. As anticipated, the chain dimensions became anisotropic, with signi®cant differences parallel and perpendicular to the direction of the particle axes. In general, the network chains tended to adopt more compressed con®gurations relative to those of prolate particles having equivalent sizes and aspect ratios. Use of these distributions in a standard molecular model for rubberlike elasticity gave values of the elongation moduli, and these were found to depend on the sizes, number, and axial ratios of the particles, as expected. In particular, the reinforcement from the oblate particles was found to be greatest in the plane of the particles, and the changes were in at least qualitative agreement with the corresponding experimental results.
Polymer, 2004
Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler parti... more Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler particles arranged either on a cubic lattice or randomly in space. Attention was first focused on the effects of the type of arrangement of the particles on the microscopic properties of the polymer chains. Specifically, Monte Carlo rotational isomeric state (MC-RIS) simulations were carried out to predict the effects of the volumes excluded by the filler particles on the configurational distribution functions of the chains, and from these distributions the elastomeric properties of the composites. The calculations were carried out for a range of particle sizes and particle volume fractions. As expected, filler inclusions are found to increase the non-Gaussian behavior of the chains. The results were compared with those from smallangle neutron scattering (SANS) experiments. In the case of arrangement on a cubic lattice, chains dimensions were always found to decrease. In the randomly-dispersed filler arrangements, there were significant increases in chain dimensions relative to the unfilled system in some instances, and the changes were in excellent agreement with the SANS results. The present simulations thus give further encouragement to interpretations of chain deformations in filled systems in terms of volume exclusion effects from the nanoparticle inclusions, including their dispersions and arrangements within polymer matrices.
Macromolecules, 2004
ABSTRACT
Journal of Macromolecular Science Part a, 2004
ABSTRACT
Nature and Science of Sleep, 2011
Collidally stabilized gold nanoparticles NPs having sizes in the range of 3-20 nm have been prepa... more Collidally stabilized gold nanoparticles NPs having sizes in the range of 3-20 nm have been prepared by citrate chemical reduction methods. The gold nanoparticles were characterized employing transmission electron microscopy TEM. The in vitro release kinetics and associated antifungal effects were investigated for Pencillium. Micro plate reader analyses were utilized for monitoring the antifungal effects. The results provided strong evidence that could warrant the consideration of gold nanoparticles as antifungal material. Such treatment could circumvent the side and passive immune effects of other antifungal material. Also, the nanoparticles thus prepared have the potential and ability of targeting specific sites.
Polymer, 2005
The elastomeric properties of networks of stereoregular polypropylenes (PP) filled with spherical... more The elastomeric properties of networks of stereoregular polypropylenes (PP) filled with spherical nanoparticles have been modeled in an attempt to obtain better insights into elastomer reinforcement. The polymers were either isotactic or syndiotactic PP in the ...
International Journal of Nanomedicine, 2011
Background: Nanosized dry powder inhalers provide higher stability for poorly water-soluble drugs... more Background: Nanosized dry powder inhalers provide higher stability for poorly water-soluble drugs as compared with liquid formulations. However, the respirable particles must have a diameter of 1-5 µm in order to deposit in the lungs. Controlled agglomeration of the nanoparticles increases their geometric particle size so they can deposit easily in the lungs. In the lungs, they fall apart to reform nanoparticles, thus enhancing the dissolution rate of the drugs. Theophylline is a bronchodilator with poor solubility in water. Methods: Nanosized theophylline colloids were formed using an amphiphilic surfactant and destabilized using dilute sodium chloride solutions to form the agglomerates. Results: The theophylline nanoparticles thus obtained had an average particle size of 290 nm and a zeta potential of −39.5 mV, whereas the agglomerates were 2.47 µm in size with a zeta potential of −28.9 mV. The release profile was found to follow first-order kinetics (r 2. 0.96). The aerodynamic characteristics of the agglomerated nanoparticles were determined using a cascade impactor. The behavior of the agglomerate was significantly better than unprocessed raw theophylline powder. In addition, the nanoparticles and agglomerates resulted in a significant improvement in the dissolution of theophylline. Conclusion: The results obtained lend support to the hypothesis that controlled agglomeration strategies provide an efficient approach for the delivery of poorly water-soluble drugs into the lungs.
Polymer, 2004
Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler parti... more Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler particles arranged either on a cubic lattice or randomly in space. Attention was first focused on the effects of the type of arrangement of the particles on the microscopic properties of the polymer chains. Specifically, Monte Carlo rotational isomeric state (MC-RIS) simulations were carried out to predict the effects of the volumes excluded by the filler particles on the configurational distribution functions of the chains, and from these distributions the elastomeric properties of the composites. The calculations were carried out for a range of particle sizes and particle volume fractions. As expected, filler inclusions are found to increase the non-Gaussian behavior of the chains. The results were compared with those from smallangle neutron scattering (SANS) experiments. In the case of arrangement on a cubic lattice, chains dimensions were always found to decrease. In the randomly-dispersed filler arrangements, there were significant increases in chain dimensions relative to the unfilled system in some instances, and the changes were in excellent agreement with the SANS results. The present simulations thus give further encouragement to interpretations of chain deformations in filled systems in terms of volume exclusion effects from the nanoparticle inclusions, including their dispersions and arrangements within polymer matrices.
Polymer, 2005
We derived the analytical solution of the eigenvalue problem for stereo-regular vinyl chains, suc... more We derived the analytical solution of the eigenvalue problem for stereo-regular vinyl chains, such as stereo-regular polypropylene chains. The solution is applicable to all stereo-regular polymers of the type (AB)x which do not have symmetry between gauche+ and gauche− states, and to polymers, such as polyoxymethylene or polydimethylsiloxane, for which symmetry between the gauche+ and gauche− states does exist. For symmetric chains, the general solution of the eigenvalue problem is reduced to the known solution for polyoxymethylene chains. To illustrate the method the calculations have been performed for the three rotational states (trans, gauche+ and gauche−) model, but the general algebraic solution is applicable for any ν rotational states models of polymer chains. We used the analytical solution of the eigenvalue problem to calculate numerically elastic properties of stereo-regular polypropylene chains within the framework of Mark–Curro theory (J Chem Phys, 79, 5705, 1983).
Materials Science and Engineering: A, 2005
A review of the recent work on polymer matrix nanocomposites is presented. This review is not int... more A review of the recent work on polymer matrix nanocomposites is presented. This review is not intended to be comprehensive, but provides an overview of the processing techniques and trends in the mechanical behavior and morphology of nanocomposites. A number of composite systems with amorphous and/or crystalline polymer matrices and different nano-sized filler materials are discussed.
Macromolecules, 2004
ABSTRACT
Journal of Polymer Science Part B: Polymer Physics, 1996
computer simulations were carried out on filled networks of poly(dimethylsiloxane) (PDMS), which ... more computer simulations were carried out on filled networks of poly(dimethylsiloxane) (PDMS), which were modeled as composites of crosslinked chains and randomly arranged spherical filler particles. The primary concern of the investigation was the effect of the excluded volume of these particles on the elastomeric properties of the polymers. Calculations were carried out for PDMS chains with different molecular masses between crosslinks, and for filler particles with different sizes and a t various volume percentages. Distributions of end-to-end vectors for both unfilled and filled networks were obtained using Monte Carlo simulations based on rotational isomeric state (RIS) theory. More extended configurations, with a higher end-to-end distance, were observed for networks filled with smaller particles. The nominal stress f * and the modulus or reduced nominal stress [f*] were calculated from the distributions of end-to-end vectors using the Mark-Curro approach. Relatively small filler particles were found to increase the non-Gaussian behavior and to increase the normalized moduli above the reference value of unity. Temperature effects on the stress were also investigated.
European Polymer Journal, 2006
Monte Carlo simulations based on rotational isomeric state models were carried out to determine h... more Monte Carlo simulations based on rotational isomeric state models were carried out to determine how amorphous polyethylene chains are deformed by the presence of spherical filler particles. The resulting distributions of the chain end-to-end distances were then employed to calculate mechanical properties of the cross-linked chains. The basic goals were (i) to refine previous simulations of this type carried out on this system to remove possible sampling biases, and (ii) to document the circumstances under which the particles stretch the chains to larger end-to-end distances, rather than compress them to smaller distances, and (iii) to study in more detail the flattening of the chains near particle surfaces. Comparisons with experiments include filler-induced changes in chain dimensions measured by neutron scattering, and general features of the stress-strain isotherms widely observed for reinforced elastomers in simple elongation.
Colloid and Polymer Science, 2006