Ioannis Tanis - Academia.edu (original) (raw)

Papers by Ioannis Tanis

Research paper thumbnail of A Molecular Dynamics Study of Single-Gas and Mixed-Gas N2 and CH4 Transport in Triptycene-Based Polyimide Membranes

Polymers, Sep 17, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Distribution of Mechanical Properties in Poly(ethylene oxide)/silica Nanocomposites via Atomistic Simulations: From the Glassy to the Liquid State

Macromolecules, Apr 29, 2024

Research paper thumbnail of Heterogeneous Glass Transition Behavior of Poly(Ethylene oxide)/Silica Nanocomposites via Atomistic MD Simulations

Research paper thumbnail of Single-gas and mixed-gas permeation of N2/CH4 in thermally-rearranged TR-PBO membranes and their 6FDA-bisAPAF polyimide precursor studied by molecular dynamics simulations

Physical Chemistry Chemical Physics

High-performance polymers with polybenzoxazole (PBO) structures, formed via thermal rearrangement... more High-performance polymers with polybenzoxazole (PBO) structures, formed via thermal rearrangement (TR) of aromatic polyimide precursors, have been developed for gas separation applications.

Research paper thumbnail of Assessment of an anisotropic coarse-grained model for cis-1,4-polybutadiene: a bottom-up approach

Soft Matter

This work presents a generic anisotropic bottom-up coarse-grained approach for polymer melts and ... more This work presents a generic anisotropic bottom-up coarse-grained approach for polymer melts and it is tested thoroughly and successfully.

Research paper thumbnail of Molecular dynamics simulation of the viscocapillary leveling of polymer films

Research paper thumbnail of A comparison of pure and mixed-gas permeation of nitrogen and methane in 6FDA-based polyimides as studied by molecular dynamics simulations

Computational Materials Science, 2018

Molecular dynamics simulations (MD) of pure nitrogen, pure methane and mixed nitrogen/methane sor... more Molecular dynamics simulations (MD) of pure nitrogen, pure methane and mixed nitrogen/methane sorption in two fluorinated homopolyimides, 6FDA-mPDA and 6FDA-durene, as well as in the block copolyimide 6FDA-mPDA/durene were conducted as a complement to a series of experimental studies of the corresponding dense flat membranes. These polyimides are known to vary significantly in their gas separation properties. Gas insertion in the model polymer matrices was carried out in a stepwise procedure in order to avoid pre-swelling and to mimic as close as possible the experimental approach. An iterative technique was used to determine the sorption isotherms for the single-component uptakes up to feed pressures exceeding 60 bar. A novel iterative method was also used to determine the mixed-gas uptakes at an elevated pressure in the models and under similar conditions to mixtures in natural gas processing. Volume dilation effects were also examined. Estimating the permselectivity of the polyimides exclusively from the results for pure gases can lead to erroneous conclusions.

Research paper thumbnail of Molecular dynamics simulation of the capillary leveling of viscoelastic polymer films

The Journal of Chemical Physics, 2017

Surface tension-driven flow techniques have recently emerged as an efficient means of shedding li... more Surface tension-driven flow techniques have recently emerged as an efficient means of shedding light into the rheology of thin polymer films. Motivated by experimental and theoretical approaches in films bearing a varying surface topography, we present results on the capillary relaxation of a square pattern at the free surface of a viscoelastic polymer film, using molecular dynamics simulations of a coarse-grained polymer model. Height profiles are monitored as a function of time after heating the system above its glass-transition temperature and their time dependence is fitted to the theory of capillary leveling. Results show that the viscosity is not constant, but time dependent. In addition to providing a complementary insight about the local inner mechanisms, our simulations of the capillary-leveling process therefore probe the viscoelasticity of the polymer and not only its viscosity, in contrast to previous experimental approaches.

Research paper thumbnail of A comparison of homopolymer and block copolymer structure in 6FDA-based polyimides

Physical chemistry chemical physics : PCCP, Jan 14, 2014

Two homopolyimides and the corresponding block copolyimide, all based on the 4,4'-(hexafluoro... more Two homopolyimides and the corresponding block copolyimide, all based on the 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), have been synthesized and fully atomistic models have been studied using molecular dynamics (MD) simulation. The respective diamines were 1,3-phenylenediamine (mPDA) and 2,3,5,6-tetramethyl-1,4-phenylenediamine (durene). These polyimides are potential candidates for gas separation applications. The synthesized polymers were processed as dense flat membranes. The effects of diamine structure were investigated at the molecular level and an attempt to compare the structural features of homo- and block copolyimides was made. Amorphous models were generated using a hybrid pivot Monte Carlo-MD sampling preparation technique. Average model densities were validated against experimental measurements on the dense films. Cohesive energies, Hildebrand solubility parameters, conformational characteristics, intermolecular interactions and available void sp...

Research paper thumbnail of Dynamics of dendritic polymers in the bulk and under confinement

AIP Conference Proceedings, 2014

The structure and dynamics of a hyperbranched polyesteramide (Hybrane  S 1200) polymer and its n... more The structure and dynamics of a hyperbranched polyesteramide (Hybrane  S 1200) polymer and its nanocomposites with natural montmorillonite (Na +-MMT) are investigated by XRD, DSC, QENS, DS and Molecular Dynamics (MD) simulation. In bulk, the energy-resolved elastically scattered intensity from the polymer exhibits two relaxation steps, one attributed to sub-T g motions and one observed at temperatures above the glass transition, T g. The QENS spectra measured over the complete temperature range are consistent with the elastic measurements and can be correlated to the results emerging from the detailed description afforded by the atomistic simulations, which predict the existence of three relaxation processes. Moreover, dielectric spectroscopy shows the sub-T g beta process as well as the segmental relaxation. For the nanocomposites, XRD reveals an intercalated structure for all hybrids with distinct interlayer distances due to polymer chains residing within the galleries of the Na +-MMT. The polymer chains confined within the galleries show similarities in the behavior with that of the polymer in the bulk for temperatures below the bulk polymer T g , whereas they exhibit frozen dynamics under confinement at temperatures higher than that.

Research paper thumbnail of Molecular Dynamics Simulations of a Hyperbranched Poly(ester amide): Statics, Dynamics, and Hydrogen Bonding

The Journal of Physical Chemistry B, 2009

Within the broad class of hyperbranched polymers, highly symmetrical objects (such as dendrimers ... more Within the broad class of hyperbranched polymers, highly symmetrical objects (such as dendrimers and Vicsek fractals) are of special theoretical interest. Here we study, using the MARTINI force-field, polyamidoamine Vicsek fractals (PVF) in silico, focusing on their structure and dynamics in dilute solution. Our extensive microsecond-long simulations show that the radius of gyration of PVF scales with the molecular weight as N 0.54 , behavior rather close to that of stars and considerably distinct from that of dendrimers. The study of the radial density profiles indicates that different parts of the PVF interpenetrate significantly, fact which stresses the soft and sparse character of PVF. These results are also supported by our findings for the rotational autocorrelation functions.

Research paper thumbnail of Modeling of hyperbranched polyesters as hosts for the multifunctional bioactive agent shikonin

Physical Chemistry Chemical Physics, 2011

We employ fully atomistic molecular dynamics simulations to study in detail the mechanisms involv... more We employ fully atomistic molecular dynamics simulations to study in detail the mechanisms involved in the non-covalent association of the bioactive agent Shikonin with the commercially available hyperbranched polyesters (Boltorn s), in ethanol solutions. We examine effects of the (pseudo)generation of the hyperbranched polyester and mimic two different concentrations, under conditions corresponding to excess drug availability. The two mechanisms participating in the polymer/drug complexation are hydrogen bonding and spatial constriction of the drug molecules within the hyperbranched structure. Based on static, as well as on dynamic information obtained by the analysis performed, it is demonstrated that apart from the size of the polyester, factors like the degree of structural flexibility, the intrapolymer hydrogen bonding and the polymer concentration may affect decisively the polyester/shikonin associative behavior, as well as the behavior of the drug-molecules in the solution. The results from the present study offer a detailed picture of the relative importance of those parameters affecting the complexation, and may serve as a basis for the understanding of the behavior of more complex multi-polyester systems.

Research paper thumbnail of Simulation of a Symmetric Binary Mixture of Charged Dendrimers Under Varying Electrostatic Interactions: Static and Dynamic Aspects

Macromolecules, 2011

A symmetric binary mixture of terminally charged trifunctional-core/difunctional-branched dendrim... more A symmetric binary mixture of terminally charged trifunctional-core/difunctional-branched dendrimers of the third and the fourth generation is examined in explicit solvent solution by means of molecular dynamics simulations. The static and dynamic response of the components is monitored under a varying strength of electrostatic interactions. The response of the dendrimer constituents shares common features as the intensity of Coulombic interactions increases, but characteristic differences are noted in the individual structural arrangement and their dynamic response. An effective-charge modulation develops across the dendritic structure and at the immediate vicinity of each molecule. The asymmetry in size and in the overall charge between the two components affects the packing properties of the molecules resulting in different morphologies compared to the respective single component systems. In addition, individual translational and rotational motion of the dendrimers exhibits distinct behavior in different Coulombic regimes. The motional contrast between the two components differentiates their relative dynamic response as the electrostatic interactions grow stronger. The increase of Coulombic interactions drives the components of the mixture to a dynamically arrested state, but the eventual vitrification takes place at different levels of electrostatic interactions depending on dendrimer generation. The findings of the present study elucidate several aspects of the behavior of these charged soft-colloidal materials and offer new insight toward the control of their long-range order and of their dynamic properties.

Research paper thumbnail of Structure and Dynamics of Hyperbranched Polymer/Layered Silicate Nanocomposites

Macromolecules, 2013

The structure and dynamics of a hyperbranched polyesteramide (Hybrane S 1200) polymer and its nan... more The structure and dynamics of a hyperbranched polyesteramide (Hybrane S 1200) polymer and its nanocomposites with natural montmorillonite (Na + −MMT) are investigated to offer a detailed picture of its behavior in bulk and under confinement. In bulk, the behavior is probed by quasi-elastic neutron scattering (QENS) with molecular dynamics simulations employed for a better insight into the relevant relaxation processes. The energy-resolved elastically scattered intensity from the polymer exhibits two distinct relaxation steps, one attributed to sub-T g motions and one observed at temperatures above the glass transition, T g. The QENS spectra measured over the complete temperature range are consistent with the elastic measurements and can be correlated to the results emerging from the detailed description afforded by the atomistic simulations, which cover a broad time range and predict the existence of three relaxation processes. The nanocomposites are investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and QENS. XRD reveals an intercalated nanocomposite structure with the polymer chains residing within the galleries of the Na + −MMT. The polymer chains confined within the galleries show similarities in the behavior with that of the polymer in the bulk for temperatures below the bulk polymer T g , whereas they exhibit frozen dynamics under confinement at temperatures higher than that.

Research paper thumbnail of Local Dynamics and Hydrogen Bonding in Hyperbranched Aliphatic Polyesters

Macromolecules, 2009

We report results from fully atomistic molecular dynamics simulations of commercially available a... more We report results from fully atomistic molecular dynamics simulations of commercially available aliphatic hydroxyl-terminated hyperbranched polyesters of two different architectures/sizes in the bulk, exploring dynamic mechanisms associated with their physical behavior as it has been described by pertinent experimental techniques. Particular emphasis is given on the role of the hydrogen-bonding capabilities of the examined systems and the impact on their local dynamic response. Analysis of the simulation results reveals that certain key aspects of their unique behavior, such as the molecular weight dependence of local group reorientation as well as the more restricted motion of these moieties in lowgeneration polyesters, can be explained by considering the distinct hydrogen-bonding pattern, which is realized at the intra-and intermolecular levels. This interconnection is shown to be realized through a coupling mechanism of local bond relaxation with the time scale pertinent to the formed hydrogen bond network. Quantitative accounts are provided for the relative percentage of the different kinds of hydrogen bonds as well as for their corresponding lifetimes. The detail afforded by the present work provides new insight into the structure/properties relation of such molecules and offers new ground for the interpretation of relevant experimental findings.

Research paper thumbnail of Complexes between Poly(amido amine) Dendrimers and Poly(methacrlyic acid): Insight from Molecular Dynamics Simulations

Macromolecular Symposia, 2013

Research paper thumbnail of Association of a Weakly Acidic Anti-Inflammatory Drug (Ibuprofen) with a Poly(Amidoamine) Dendrimer as Studied by Molecular Dynamics Simulations

The Journal of Physical Chemistry B, 2009

In this work, we report results from fully atomistic molecular dynamics simulations regarding the... more In this work, we report results from fully atomistic molecular dynamics simulations regarding the associative behavior of a third-generation poly(amidoamine) dendrimer with ibuprofen, a weakly acidic nonsteroidal anti-inflammatory drug, in aqueous solutions and at different pH conditions. Employing a combined static and dynamic approach, we describe the specifics of the complexation/encapsulation of the drug within the dendritic structure. In addition, information regarding the dynamic behavior is provided for the self-and the collective motion of the drug molecules. The detail afforded by the present molecular-level description of the relevant associative mechanisms (i.e., electrostatic complexation, hydrogen-bonding), provides a deeper insight for the interpretation of recent experimental findings regarding the behavior of dendrimer/ibuprofen systems in an aqueous environment.

Research paper thumbnail of A Molecular Dynamics Study of Single-Gas and Mixed-Gas N2 and CH4 Transport in Triptycene-Based Polyimide Membranes

Polymers, Sep 17, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Research paper thumbnail of Distribution of Mechanical Properties in Poly(ethylene oxide)/silica Nanocomposites via Atomistic Simulations: From the Glassy to the Liquid State

Macromolecules, Apr 29, 2024

Research paper thumbnail of Heterogeneous Glass Transition Behavior of Poly(Ethylene oxide)/Silica Nanocomposites via Atomistic MD Simulations

Research paper thumbnail of Single-gas and mixed-gas permeation of N2/CH4 in thermally-rearranged TR-PBO membranes and their 6FDA-bisAPAF polyimide precursor studied by molecular dynamics simulations

Physical Chemistry Chemical Physics

High-performance polymers with polybenzoxazole (PBO) structures, formed via thermal rearrangement... more High-performance polymers with polybenzoxazole (PBO) structures, formed via thermal rearrangement (TR) of aromatic polyimide precursors, have been developed for gas separation applications.

Research paper thumbnail of Assessment of an anisotropic coarse-grained model for cis-1,4-polybutadiene: a bottom-up approach

Soft Matter

This work presents a generic anisotropic bottom-up coarse-grained approach for polymer melts and ... more This work presents a generic anisotropic bottom-up coarse-grained approach for polymer melts and it is tested thoroughly and successfully.

Research paper thumbnail of Molecular dynamics simulation of the viscocapillary leveling of polymer films

Research paper thumbnail of A comparison of pure and mixed-gas permeation of nitrogen and methane in 6FDA-based polyimides as studied by molecular dynamics simulations

Computational Materials Science, 2018

Molecular dynamics simulations (MD) of pure nitrogen, pure methane and mixed nitrogen/methane sor... more Molecular dynamics simulations (MD) of pure nitrogen, pure methane and mixed nitrogen/methane sorption in two fluorinated homopolyimides, 6FDA-mPDA and 6FDA-durene, as well as in the block copolyimide 6FDA-mPDA/durene were conducted as a complement to a series of experimental studies of the corresponding dense flat membranes. These polyimides are known to vary significantly in their gas separation properties. Gas insertion in the model polymer matrices was carried out in a stepwise procedure in order to avoid pre-swelling and to mimic as close as possible the experimental approach. An iterative technique was used to determine the sorption isotherms for the single-component uptakes up to feed pressures exceeding 60 bar. A novel iterative method was also used to determine the mixed-gas uptakes at an elevated pressure in the models and under similar conditions to mixtures in natural gas processing. Volume dilation effects were also examined. Estimating the permselectivity of the polyimides exclusively from the results for pure gases can lead to erroneous conclusions.

Research paper thumbnail of Molecular dynamics simulation of the capillary leveling of viscoelastic polymer films

The Journal of Chemical Physics, 2017

Surface tension-driven flow techniques have recently emerged as an efficient means of shedding li... more Surface tension-driven flow techniques have recently emerged as an efficient means of shedding light into the rheology of thin polymer films. Motivated by experimental and theoretical approaches in films bearing a varying surface topography, we present results on the capillary relaxation of a square pattern at the free surface of a viscoelastic polymer film, using molecular dynamics simulations of a coarse-grained polymer model. Height profiles are monitored as a function of time after heating the system above its glass-transition temperature and their time dependence is fitted to the theory of capillary leveling. Results show that the viscosity is not constant, but time dependent. In addition to providing a complementary insight about the local inner mechanisms, our simulations of the capillary-leveling process therefore probe the viscoelasticity of the polymer and not only its viscosity, in contrast to previous experimental approaches.

Research paper thumbnail of A comparison of homopolymer and block copolymer structure in 6FDA-based polyimides

Physical chemistry chemical physics : PCCP, Jan 14, 2014

Two homopolyimides and the corresponding block copolyimide, all based on the 4,4'-(hexafluoro... more Two homopolyimides and the corresponding block copolyimide, all based on the 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), have been synthesized and fully atomistic models have been studied using molecular dynamics (MD) simulation. The respective diamines were 1,3-phenylenediamine (mPDA) and 2,3,5,6-tetramethyl-1,4-phenylenediamine (durene). These polyimides are potential candidates for gas separation applications. The synthesized polymers were processed as dense flat membranes. The effects of diamine structure were investigated at the molecular level and an attempt to compare the structural features of homo- and block copolyimides was made. Amorphous models were generated using a hybrid pivot Monte Carlo-MD sampling preparation technique. Average model densities were validated against experimental measurements on the dense films. Cohesive energies, Hildebrand solubility parameters, conformational characteristics, intermolecular interactions and available void sp...

Research paper thumbnail of Dynamics of dendritic polymers in the bulk and under confinement

AIP Conference Proceedings, 2014

The structure and dynamics of a hyperbranched polyesteramide (Hybrane  S 1200) polymer and its n... more The structure and dynamics of a hyperbranched polyesteramide (Hybrane  S 1200) polymer and its nanocomposites with natural montmorillonite (Na +-MMT) are investigated by XRD, DSC, QENS, DS and Molecular Dynamics (MD) simulation. In bulk, the energy-resolved elastically scattered intensity from the polymer exhibits two relaxation steps, one attributed to sub-T g motions and one observed at temperatures above the glass transition, T g. The QENS spectra measured over the complete temperature range are consistent with the elastic measurements and can be correlated to the results emerging from the detailed description afforded by the atomistic simulations, which predict the existence of three relaxation processes. Moreover, dielectric spectroscopy shows the sub-T g beta process as well as the segmental relaxation. For the nanocomposites, XRD reveals an intercalated structure for all hybrids with distinct interlayer distances due to polymer chains residing within the galleries of the Na +-MMT. The polymer chains confined within the galleries show similarities in the behavior with that of the polymer in the bulk for temperatures below the bulk polymer T g , whereas they exhibit frozen dynamics under confinement at temperatures higher than that.

Research paper thumbnail of Molecular Dynamics Simulations of a Hyperbranched Poly(ester amide): Statics, Dynamics, and Hydrogen Bonding

The Journal of Physical Chemistry B, 2009

Within the broad class of hyperbranched polymers, highly symmetrical objects (such as dendrimers ... more Within the broad class of hyperbranched polymers, highly symmetrical objects (such as dendrimers and Vicsek fractals) are of special theoretical interest. Here we study, using the MARTINI force-field, polyamidoamine Vicsek fractals (PVF) in silico, focusing on their structure and dynamics in dilute solution. Our extensive microsecond-long simulations show that the radius of gyration of PVF scales with the molecular weight as N 0.54 , behavior rather close to that of stars and considerably distinct from that of dendrimers. The study of the radial density profiles indicates that different parts of the PVF interpenetrate significantly, fact which stresses the soft and sparse character of PVF. These results are also supported by our findings for the rotational autocorrelation functions.

Research paper thumbnail of Modeling of hyperbranched polyesters as hosts for the multifunctional bioactive agent shikonin

Physical Chemistry Chemical Physics, 2011

We employ fully atomistic molecular dynamics simulations to study in detail the mechanisms involv... more We employ fully atomistic molecular dynamics simulations to study in detail the mechanisms involved in the non-covalent association of the bioactive agent Shikonin with the commercially available hyperbranched polyesters (Boltorn s), in ethanol solutions. We examine effects of the (pseudo)generation of the hyperbranched polyester and mimic two different concentrations, under conditions corresponding to excess drug availability. The two mechanisms participating in the polymer/drug complexation are hydrogen bonding and spatial constriction of the drug molecules within the hyperbranched structure. Based on static, as well as on dynamic information obtained by the analysis performed, it is demonstrated that apart from the size of the polyester, factors like the degree of structural flexibility, the intrapolymer hydrogen bonding and the polymer concentration may affect decisively the polyester/shikonin associative behavior, as well as the behavior of the drug-molecules in the solution. The results from the present study offer a detailed picture of the relative importance of those parameters affecting the complexation, and may serve as a basis for the understanding of the behavior of more complex multi-polyester systems.

Research paper thumbnail of Simulation of a Symmetric Binary Mixture of Charged Dendrimers Under Varying Electrostatic Interactions: Static and Dynamic Aspects

Macromolecules, 2011

A symmetric binary mixture of terminally charged trifunctional-core/difunctional-branched dendrim... more A symmetric binary mixture of terminally charged trifunctional-core/difunctional-branched dendrimers of the third and the fourth generation is examined in explicit solvent solution by means of molecular dynamics simulations. The static and dynamic response of the components is monitored under a varying strength of electrostatic interactions. The response of the dendrimer constituents shares common features as the intensity of Coulombic interactions increases, but characteristic differences are noted in the individual structural arrangement and their dynamic response. An effective-charge modulation develops across the dendritic structure and at the immediate vicinity of each molecule. The asymmetry in size and in the overall charge between the two components affects the packing properties of the molecules resulting in different morphologies compared to the respective single component systems. In addition, individual translational and rotational motion of the dendrimers exhibits distinct behavior in different Coulombic regimes. The motional contrast between the two components differentiates their relative dynamic response as the electrostatic interactions grow stronger. The increase of Coulombic interactions drives the components of the mixture to a dynamically arrested state, but the eventual vitrification takes place at different levels of electrostatic interactions depending on dendrimer generation. The findings of the present study elucidate several aspects of the behavior of these charged soft-colloidal materials and offer new insight toward the control of their long-range order and of their dynamic properties.

Research paper thumbnail of Structure and Dynamics of Hyperbranched Polymer/Layered Silicate Nanocomposites

Macromolecules, 2013

The structure and dynamics of a hyperbranched polyesteramide (Hybrane S 1200) polymer and its nan... more The structure and dynamics of a hyperbranched polyesteramide (Hybrane S 1200) polymer and its nanocomposites with natural montmorillonite (Na + −MMT) are investigated to offer a detailed picture of its behavior in bulk and under confinement. In bulk, the behavior is probed by quasi-elastic neutron scattering (QENS) with molecular dynamics simulations employed for a better insight into the relevant relaxation processes. The energy-resolved elastically scattered intensity from the polymer exhibits two distinct relaxation steps, one attributed to sub-T g motions and one observed at temperatures above the glass transition, T g. The QENS spectra measured over the complete temperature range are consistent with the elastic measurements and can be correlated to the results emerging from the detailed description afforded by the atomistic simulations, which cover a broad time range and predict the existence of three relaxation processes. The nanocomposites are investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and QENS. XRD reveals an intercalated nanocomposite structure with the polymer chains residing within the galleries of the Na + −MMT. The polymer chains confined within the galleries show similarities in the behavior with that of the polymer in the bulk for temperatures below the bulk polymer T g , whereas they exhibit frozen dynamics under confinement at temperatures higher than that.

Research paper thumbnail of Local Dynamics and Hydrogen Bonding in Hyperbranched Aliphatic Polyesters

Macromolecules, 2009

We report results from fully atomistic molecular dynamics simulations of commercially available a... more We report results from fully atomistic molecular dynamics simulations of commercially available aliphatic hydroxyl-terminated hyperbranched polyesters of two different architectures/sizes in the bulk, exploring dynamic mechanisms associated with their physical behavior as it has been described by pertinent experimental techniques. Particular emphasis is given on the role of the hydrogen-bonding capabilities of the examined systems and the impact on their local dynamic response. Analysis of the simulation results reveals that certain key aspects of their unique behavior, such as the molecular weight dependence of local group reorientation as well as the more restricted motion of these moieties in lowgeneration polyesters, can be explained by considering the distinct hydrogen-bonding pattern, which is realized at the intra-and intermolecular levels. This interconnection is shown to be realized through a coupling mechanism of local bond relaxation with the time scale pertinent to the formed hydrogen bond network. Quantitative accounts are provided for the relative percentage of the different kinds of hydrogen bonds as well as for their corresponding lifetimes. The detail afforded by the present work provides new insight into the structure/properties relation of such molecules and offers new ground for the interpretation of relevant experimental findings.

Research paper thumbnail of Complexes between Poly(amido amine) Dendrimers and Poly(methacrlyic acid): Insight from Molecular Dynamics Simulations

Macromolecular Symposia, 2013

Research paper thumbnail of Association of a Weakly Acidic Anti-Inflammatory Drug (Ibuprofen) with a Poly(Amidoamine) Dendrimer as Studied by Molecular Dynamics Simulations

The Journal of Physical Chemistry B, 2009

In this work, we report results from fully atomistic molecular dynamics simulations regarding the... more In this work, we report results from fully atomistic molecular dynamics simulations regarding the associative behavior of a third-generation poly(amidoamine) dendrimer with ibuprofen, a weakly acidic nonsteroidal anti-inflammatory drug, in aqueous solutions and at different pH conditions. Employing a combined static and dynamic approach, we describe the specifics of the complexation/encapsulation of the drug within the dendritic structure. In addition, information regarding the dynamic behavior is provided for the self-and the collective motion of the drug molecules. The detail afforded by the present molecular-level description of the relevant associative mechanisms (i.e., electrostatic complexation, hydrogen-bonding), provides a deeper insight for the interpretation of recent experimental findings regarding the behavior of dendrimer/ibuprofen systems in an aqueous environment.