Chain flexibility for tuning effective interactions in blends of polymers and polymer-grafted nanoparticles

Soft Matter ◽  
2014 ◽  
Vol 10 (35) ◽  
pp. 6777-6782 ◽  
Author(s):  
Babji Palli ◽  
Venkat Padmanabhan
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Potential Of Mean Force ◽  
Chain Flexibility ◽  
Effective Interactions ◽  
Grafted Nanoparticles ◽  
Dynamics Simulations

We present molecular dynamics simulations of polymer-grafted nanoparticles in a homopolymer matrix to demonstrate the effect of chain flexibility on the potential of mean force (PMF) between various species in the nanocomposite.

scholarly journals Polyelectrolyte-Nanoplatelet Complexation: Is It Possible to Predict the State Diagram?

2019 ◽  
Vol 20 (24) ◽  
pp. 6217
Author(s):  
Maria Jansson ◽  
Marie Skepö
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
State Diagram ◽  
Charge Ratio ◽  
Coarse Grained ◽  
Total Charge ◽  
Linear Charge Density ◽  
Chain Flexibility ◽  
Dynamics Simulations ◽  
Oppositely Charged

The addition of polyelectrolytes (PEs) to suspensions of charged colloids, such as nanoplatelets (NPs), is of great interest due to their specific feature of being either a stabilizing or a destabilizing agent. Here, the complexation between a PE and oppositely charged NPs is studied utilizing coarse-grained molecular dynamics simulations based on the continuum model. The complex formation is evaluated with respect to the stoichiometric charge-ratio within the system, as well as by the alternation of the chain properties. It is found that the formed complexes can possess either an extended or a compact shape. Moreover, it is observed that the chain can become overcharged by the oppositely charged NPs. With an increase in chain length, or a decrease in chain flexibility, the complex obtains a more extended shape, where the NPs are less tightly bound to the PE. The latter is also true when reducing the total charge of the chain by varying the linear charge density, whereas in this case, the chain contracts. With our coarse-grained model and molecular dynamics simulations, we are able to predict the composition and the shape of the formed complex and how it is affected by the characteristics of the chain. The take-home message is that the complexation between PEs and NPs results in a versatile and rich state diagram, which indeed is difficult to predict, and dependent on the properties of the chain and the model used. Thus, we propose that the present model can be a useful tool to achieve an understanding of the PE-NPs complexation, a system commonly used in industrial and in technological processes.

Molecular Dynamics Simulations of Carbon Nanotube Interactions in Water/Surfactant Systems

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Nasir M. Uddin ◽  
Franco Capaldi ◽  
Bakhtier Farouk
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Potential Of Mean Force ◽  
Quantitative Prediction ◽  
The Matrix ◽  
Adaptive Biasing ◽  
Speed Up ◽  
Dynamics Simulations ◽  
Processing Techniques ◽  
Walled Carbon Nanotubes

The properties of nanocomposite materials depend on the dispersion of the nanoparticles/nanofibers within the matrix. The addition of surfactants and varied processing techniques are used to increase the dispersion of the nanoparticles in the final composite. A method for the quantitative prediction of the interactions between nanoparticles in solution would aid in the design of processing schedules. In this study, molecular dynamics simulations are used to compute for the potential of mean force as a function of the distance and orientation between a pair of single-walled carbon nanotubes (CNTs) in water. An adaptive biasing force method is used to speed up the calculations. Simulation results show that CNT orientation and the addition of surfactant can significantly affect CNT interactions and inturn dispersion.

scholarly journals Formation Mechanism of Ion Channel in Channelrhodopsin-2: Molecular Dynamics Simulation and Steering Molecular Dynamics Simulations

2019 ◽  
Vol 20 (15) ◽  
pp. 3780 ◽  
Author(s):  
Ting Yang ◽  
Wenying Zhang ◽  
Jie Cheng ◽  
Yanhong Nie ◽  
Qi Xin ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ion Channel ◽  
Molecular Dynamics Simulations ◽  
Formation Mechanism ◽  
Binding Sites ◽  
Electrostatic Interactions ◽  
Potential Of Mean Force ◽  
Dynamics Simulation ◽  
Cationic Channel ◽  
Dynamics Simulations

Channelrhodopsin-2 (ChR2) is a light-activated and non-selective cationic channel protein that can be easily expressed in specific neurons to control neuronal activity by light. Although ChR2 has been extensively used as an optogenetic tool in neuroscience research, the molecular mechanism of cation channel formation following retinal photoisomerization in ChR2 is not well understood. In this paper, studies of the closed and opened state ChR2 structures are presented. The formation of the cationic channel is elucidated in atomic detail using molecular dynamics simulations on the all-trans-retinal (ChR2-trans) configuration of ChR2 and its isomerization products, 13-cis-retinal (ChR2-cis) configuration, respectively. Photoisomerization of the retinal-chromophore causes the destruction of interactions among the crucial residues (e.g., E90, E82, N258, and R268) around the channel and the extended H-bond network mediated by numerous water molecules, which opens the pore. Steering molecular dynamics (SMD) simulations show that the electrostatic interactions at the binding sites in intracellular gate (ICG) and central gate (CG) can influence the transmembrane transport of Na+ in ChR2-cis obviously. Potential of mean force (PMF) constructed by SMD and umbrella sampling also found the existing energy wells at these two binding sites during the transportation of Na+. These wells partly hinder the penetration of Na+ into cytoplasm through the ion channel. This investigation provides a theoretical insight on the formation mechanism of ion channels and the mechanism of ion permeation.

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