Investigation of the interface between polyethylene and functionalized graphene: A computer simulation study

S. Javan Nikkhah,M.R. Moghbeli,S.M. Hashemianzadeh 한국물리학회 2015 Current Applied Physics Vol.15 No.10

The effect of surface chemical functionalization of a single graphene layer on its thermodynamic work of adhesion (WA) with polyethylene (PE) chains has been investigated using molecular dynamics (MD) simulation. For this purpose, amine (NH2), carboxyl (COOH), hydroxyl (OH), and methyl (CH3) functional groups were distributed randomly throughout the graphene surface using a Monte Carlo (MC) algorithm to achieve graphene functionalized structures with minimized potential energies. The MD simulation results showed that the thermodynamic WA between the PE and the functionalized graphene was larger than that between the PE and the pristine graphene. In fact, the electronegativity of functional groups and Van der Waals forces play influential roles in the thermodynamic WA between the PE and the functionalized graphene. In addition, the amount of thermodynamic WA was increased with increasing the functional group surface density, except for the graphene functionalized with the methyl groups. The segmental density of the PE chains near the single sheet surface was determined based on the density profile calculation. The polymer segments exhibited strong ordering and sharp density variations near the PE/graphene interface. The dynamic of chains was quantitatively characterized by calculating mean square displacement (MSD). Furthermore, the influence of functionality on the glass transition temperature (Tg) of the PE at the PE/graphene interface region was investigated. The results showed that the Tg at the PE/graphene interface was much higher than that of the bulk polymer. In fact, the functionalization of the graphene surface seems to considerably enhance the Tg of the polymer due to lowering the chains mobility.

Genetic Diversity of Fusarium proliferatum Populations from Maize, Onion, Rice and Sugarcane in Iran Based on Vegetative Compatibility Grouping

Alizadeh, Alireza,Javan-Nikkhah, Mohammad,Fotouhifar, Khalil-Berdi,Motlagh, Elahe Rabiee,Rahjoo, Vahid The Korean Society of Plant Pathology 2010 Plant Pathology Journal Vol.26 No.3

Fusarium proliferatum is the causal agent of stalk and root rot disease of maize, foot rot disease of rice, basal and root rot disease of onion and knife cut disease of sugarcane in Iran. In recent years, incidence and severity of these diseases have been increased in Iran. Fifty seven F. proliferatum single-spore isolates collected from diseased maize, rice, onion and sugarcane plants at different areas were used to study genetic diversity by determination of vegetative compatibility groups (VCGs). Chlorate-resistant nitrate non-utilizing (nit) mutants were recovered from selected isolates of F. proliferatum and used in complementation tests. All isolates in which both nit1 and NitM (or nit3) mutants were recovered, demonstrated self-compatibility. Vegetative compatibility tests by pairing nit mutants identified 30 VCGs among 57 isolates. Twenty-three isolates belonged to singlemember VCGs and the remaining 34 isolates, belonged to other seven multimember VCGs. Segregation of F. proliferatum isolates obtained from various area and host plants into different VCGs in Iran is reported for the first time. In this study, none of isolates obtained from rice complemented with any other isolates from onion and sugarcane and, non complementation occurred between onion and sugarcane isolates. Also, only one complementation occurred between one isolate of maize and one isolate of sugarcane and rice. Thus, a correlation between VCGs grouping and host preferences was founded. It is concluded that natural populations of F. proliferatum in Iran are probably genetically divergent and include isolates representing a potential risk for disease development.

Genetic Diversity of Fusarium proliferatum Populations from Maize, Onion, Rice and Sugarcane in Iran Based on Vegetative Compatibility Grouping

Alireza Alizadeh,Mohammad Javan-Nikkhah,Khalil-Berdi Fotouhifar,Elahe Rabiee Motlagh,Vahid Rahjoo 한국식물병리학회 2010 Plant Pathology Journal Vol.26 No.3

Fusarium proliferatum is the causal agent of stalk and root rot disease of maize, foot rot disease of rice, basal and root rot disease of onion and knife cut disease of sugarcane in Iran. In recent years, incidence and severity of these diseases have been increased in Iran. Fifty seven F. proliferatum single-spore isolates collected from diseased maize, rice, onion and sugarcane plants at different areas were used to study genetic diversity by determination of vegetative compatibility groups (VCGs). Chlorate-resistant nitrate non-utilizing (nit) mutants were recovered from selected isolates of F. proliferatum and used in complementation tests. All isolates in which both nit1 and NitM (or nit3) mutants were recovered,demonstrated self-compatibility. Vegetative compatibility tests by pairing nit mutants identified 30 VCGs among 57 isolates. Twenty-three isolates belonged to singlemember VCGs and the remaining 34 isolates, belonged to other seven multimember VCGs. Segregation of F. proliferatum isolates obtained from various area and host plants into different VCGs in Iran is reported for the first time. In this study, none of isolates obtained from rice complemented with any other isolates from onion and sugarcane and, non complementation occurred between onion and sugarcane isolates. Also, only one complementation occurred between one isolate of maize and one isolate of sugarcane and rice. Thus, a correlation between VCGs grouping and host preferences was founded. It is concluded that natural populations of F. proliferatum in Iran are probably genetically divergent and include isolates representing a potential risk for disease development.

A comprehensive molecular dynamics study of a single polystyrene chain in a good solvent

Sajad Rasouli,Mohammad Reza Moghbeli,Sousa Javan Nikkhah 한국물리학회 2018 Current Applied Physics Vol.18 No.1

In this study, molecular characteristics of polystyrene (PS) was calculated measuring its dilute-solution properties in toluene at 288.15 K via molecular dynamics (MD) simulations. The solution models consisted of PS chains with different number of repeating units all of which were in a dilute regime. In order to investigate the compatibility between the polymer and the solvent molecules, interaction energy and Flory-Huggins (FH) interaction parameter were estimated. The simulation results indicate that increasing the chain repeating units enhanced the interaction between the solute and the solvent. Additionally, the chain dimensions were evaluated calculating the radius of gyration (Rg) and end-to-end distance, r0. To determine the dynamic behavior of the chains in the solutions, mean square displacement (MSD) and diffusivity coefficient were calculated. The simulation results indicated that the chain rigidity at low molecular weight and chain flexibility with increasing the molecular weight influenced chains dynamic behavior and diffusivity. Moreover, radial distribution function (RDF) illustrated the effect of steric hindrance of the chains in dilute solution on capturing the solvent molecules. In addition, solution viscosity was calculated by performing non-equilibrium molecular dynamics simulation (NEMD). The obtained results of chain characteristics and viscosity showed a good agreement with experimental results published previously. This agreement confirms the accuracy of the applied simulation method to characterize the dilute solutions and the chains characteristics.

Molecular Dynamics (MD) Simulation of Zwitterion-Functionalized PMMA with Hydrophilic and Antifouling Surface Characteristics

Pedram Vousoughi,Mohammad Reza Moghbeli,Sousa Javan Nikkhah 한국고분자학회 2019 Macromolecular Research Vol.27 No.12

In this study, the effect of surface functionalization of poly (methyl methacrylate) (PMMA) layer using [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide, a zwitterion comonomer, on PMMA’s hydrophilicity and antifouling properties was investigated via the utilization of a molecular dynamics (MD) simulation. The modified layers were composed of PMMA chains with 30 repeating units, which were surface functionalized using various amount of zwitterionic comonomers, i.e. 0, 6.66, 9.99 and 16.65 wt%. In this case, the hydrophobicity of the resultant layer was evaluated calculating the contact angle values. Additionally, the calculated contact angles using water and diiodomethane over the PMMA model were compared to experimental values to validate the simulation procedure. To investigate the antifouling property, both the top and bottom models faces were contacted to a given feed composed of a water/ hydrocarbon mixed solvent ratio, 60/40 (vol/vol). Likewise, the number density and radial distribution function (RDF) were determined to investigate the change in the solvent molecules repulsion or organic antifouling property of the layer surface, along with increasing the content of the functionalizing groups.

Coil-to-globule transition of thermo-responsive γ-substituted poly (ɛ-caprolactone) in water: A molecular dynamics simulation study

Amin Koochaki,Mohammad Reza Moghbeli,Sousa Javan Nikkhah 한국물리학회 2018 Current Applied Physics Vol.18 No.11

The coil-to-globule behavior of poly{γ-2-[2-(2methoxyethoxy)ethoxy]ethoxy-3-caprolactone} (PMEEECL) as a γ- substituted poly (ɛ-caprolactone) was investigated via atomistic molecular dynamics (MD) simulation. For this purpose, radius of gyration, end-to-end distance and radial distribution function of the chain in the presence of water were calculated. Consequently, the lower critical solution temperature (LCST) of PMEEECL chain at which the coil-to-globule transition takes place, was determined in each calculated parameter curve. The simulation results indicated that the LCST of PMEEECL was occurred at close to 320 K, which is in a good agreement with previous experimental results. Additionally, the appearance of sudden change in both Flory-Huggins interaction parameter (χ) and interaction energy between the PMEEECL chain and water molecules at about 320 K confirmed the calculated LCST result. The radial distribution function (RDF) results showed that the affinity of the PMEEECL side chain to water molecules is lower than its backbone.