Orientation of liquid crystal monolayers on polyimide alignment layers: A molecular dynamics simulation study

Vegt, Nico F. A. van der; Müller‐Plathe, Florian; Gelessus, Achim; Johannsmann, Diethelm

doi:10.1063/1.1415498

Cited by 26 publications

(15 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other reasons, such as the influence of the combination rules for the polyimide-gas cross-term parameters 82 and the surface effect, 83 are currently being investigated.…”

Section: Discussionmentioning

confidence: 99%

Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

2004

View full text Add to dashboard Cite

The dependence of gas permeation on system size in glassy polymers has been tested by creating several models containing different numbers of molecules of the same chain length for the ODPA-ODA homopolyimide and by subsequently determining the permeation characteristics of helium. Eight "standard size" 4150-atom, a 6225-atom, and a much more expensive computationally 56025-atom systems were generated using hybrid pivot Monte Carlo (PMC)-molecular dynamics (MD) single-chain sampling. Following the careful relaxation of the polyimide matrices, helium atoms were then inserted into these systems, and MD simulations were carried out at the same applied external conditions of constant temperature and pressure tensor. Average densities for the pure matrices all fell within 0.7% of the experimental value. Energetic and structural properties as well as solubilities and characterization of the void space were also found to be number independent, thus showing that the preparation procedure gives reproducible and reliable results. Helium diffusion was analyzed over periods up to 20 ns using different approaches, such as observation of the individual trajectories, mean-square displacements, distributions of penetrant displacements components, and van Hove correlation functions. No number dependence could be detected, whether the gas molecules were in the anomalous or in the Fickian regime.

show abstract

“…Other reasons, such as the influence of the combination rules for the polyimide-gas cross-term parameters 82 and the surface effect, 83 are currently being investigated.…”

Section: Discussionmentioning

confidence: 99%

Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

2004

View full text Add to dashboard Cite

show abstract

“…Correcting the potential energy only once still does not yet lead to a correct RDF. However, the process can be iterated until the potential V n (r) and the RDF n (r) generated from it are self-consistent, Equation (10).…”

Section: Continuous Models With Numerical Potentialsmentioning

confidence: 99%

Coarse-Graining in Polymer Simulation: From the Atomistic to the Mesoscopic Scale and Back

2002

View full text Add to dashboard Cite

Polymers can be theoretically and computationally described by models pertaining to different length scales and corresponding time scales. These models have traditionally been used independently of each other. Recently, considerable progress has been made in systematically linking models of different scales. This Review focuses on the generation of lattice and off‐lattice coarse‐grained polymer models, whose “monomers” correspond to roughly a chemical repeat unit, from chemically detailed atomistic simulations of the same polymers. Computational methods are described as well as applications to polymers in the melt and in solution. The success of multiscale simulations in solving real‐world polymer problems that could not be solved in any other way suggests that they will have an important role to play in the future.

show abstract

“…MD simulations demonstrated that an aligned polyimide monolayer has the orientating ability for liquid crystal molecules. 32,33 Although the monolayer shows the atomic grooves on which the LC molecules are oriented, 33 the grooves are not as charged as those of PTFE. We presume that the difference in groove charge is the reason why a remarkable S ex value exceeding 0.95 has never been reported for polyimide.…”

Section: ¹1mentioning

confidence: 99%

Poly(tetrafluoroethylene) is Unique for Orienting Molecules

Tanaka

Ishitobi

2018

Chem. Lett.

View full text Add to dashboard Cite

A physical insight regarding poly(tetrafluoroethylene) (PTFE) is revealed herein. The driving force for the oriented growth of materials on aligned PTFE is investigated. The growth has been reported in numerous publications for a wide range of deposited materials on aligned PTFE layers since its discovery in 1991 because it is a promising method for preparing ordered molecular films. MD model simulations demonstrate herein that the shallow charged atomic grooves between adjacent PTFE chains trap typical two linear molecules, thus explaining the remarkable degrees of uniaxial orientation in their deposited thin films on the layers. Charge modifications to the model demonstrate for the first time that the negative charge of its fluorine atoms is crucial for the remarkable degrees. Hence, such an orientation is only possible with PTFE. Poly(tetrafluoroethylene) (PTFE) is regarded as the king of specialty plastic since its accidental discovery in 1938 by Plunkett.1 Currently, approximately 10 5 tons of PTFE is produced every year.2 Although this amount does account not for 1% of whole synthetic plastic, PTFE plays an irreplaceable role in various applications ranging from non-stick frying pans for kitchens to the chamber lining for corrosive uranium hexafluoride.2 Without PTFE, two atomic bombs would not have exploded in Japan. The outstanding character of PTFE is attributable to its robust CF bonds, which render PTFE extremely inert. 3The first author was specifically interested by a letter 4 and we have been keeping this first interest for over two decades. The oriented growth on PTFE was reported there and it is a promising method for preparing ordered molecular films; highly aligned PTFE thin layers are prepared by friction-transfer (FT) (or a rubbing procedure found later by us), 5 and the materials are merely deposited on the layers. Furthermore, linear molecules such as 1 (Figure 1) nanotubes, 25 and nanocomposites 26 ). For applying their thin films to molecular devices, such orientation is needed to enhance their functions such as carrier mobility 13,2729 and nonlinear optical properties. 7,12 Moreover, an intrinsic query has been nourishing our interest for so long. It remains unknown why this remarkable orientation takes place on extremely inert PTFE layers, e.g., nonsticking and poor wetting materials. An interesting question is: what happens between the orienting molecules and inert PTFE?Linear molecules orient along the atomic grooves between adjacent PTFE chains. We demonstrated previously through an MD simulation that the atomic grooves align some linear molecules including 1 (Figure 1) by trapping them along the grooves. 11The direction of linear molecules should be thus oriented in their early nuclei on which the growth further takes place somewhat epitaxially. Such grooves are shown in Figures 1a1c. However, it has been an open question whether the strong negative charge of F also contributes to trapping on the grooves or not. We report herein such a contribution for the first time.If this atomi...

show abstract

Orientation of liquid crystal monolayers on polyimide alignment layers: A molecular dynamics simulation study

Cited by 26 publications

References 47 publications

Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

Coarse-Graining in Polymer Simulation: From the Atomistic to the Mesoscopic Scale and Back

Poly(tetrafluoroethylene) is Unique for Orienting Molecules

Contact Info

Product

Resources

About