Polymers field simulation

An area of great interest in the polymer chemistry field is structure-activity relationships. In the simplest form, these can be qualitative descriptions, such as the observation that branched polymers are more biodegradable than straight-chain polymers. Computational simulations are more often directed toward the quantitative prediction of properties, such as the tensile strength of the bulk material. 

N. Tessler and Y. Roichman, Two-dimensional simulation of polymer field-efFect transistor , Applied Physics Letters 79, 2987 (2001). 

In the development of atomistic polymer models some of the milestones were Flory s rotational isomeric state (RIS) model and the development of force field simulations of polymers which led to, and have been significantly developed in the context of commercial molecular modelling software. 

A pronounced bimodal distribution of chain conformations in a micelle that contains about 10 chains is something that one would hardly expect in an equilibrium system, even though bimodal distributions have been tentatively proposed for some other equilibrium polymer systems [145]. To elucidate the studied problem, we performed a series of simulations for modified micellar shells using the MC technique for neutral systems and the combined MC-mean field simulation. The simulations are described later (see Sect. 4.2). 

FIGURE 7.9 Experimental and transmission line simulation results (colored and dashed lines, respectively) of OFET charging current for different gate voltages (Vd= —8 [V]). All of the simulations are with the same parameters V7- = —3.6 [V], /r = 1.4 x 10 " [cm /V s], and I aise = 9 x 10 [Aj. (From Roichman, Y. and Tessler, N., Tum-on and Charge Build-Up Dynamics in Polymer Field Effect Transistors, San Francisco MRS, 2005. With permission.)... 

In the polymer field, XRD and neutron scattering are the two most widely used techniques for validating results from MD simulations. Whereas XRD experiments can provide structural features over the relevant length scales, neutron scattering can reveal both structural and dynamic properties. Studies that combine MD simulations with one or both of these experimental tools have been relatively few in number, but interest in this approach is growing because of obvious synergies. 

Studying fluctuations beyond the Gaussian approximation is difficult. Special types of fluctuations, e.g., capillary waves of interfaces, can sometimes be described analytically within suitable approximations [58]. The only truly general methods are however computer simulations. Here we shall discuss two different approaches to simulating field theories for polymers Langevin simulations and Monte Carlo simulations. 

Measurement of transport parameters The main measurement of interest under this heading is of the excluded/inaccessible pore volume (IPV) of polymer relative to tracer as parameterised by the core permeability. If this quantity is known, then it should be included in the simulation studies since it may have some effect on the relative breakthrough times of polymer and tracer. However, it has been found that the IPV effect is usually dominated by the frontal retardation of the polymer as a result of adsorption/retention, and it is not generally of major importance in the assessment of the outcome of the polymer flood. Other measurements, such as of polymer dispersion coefficient and viscous fingering parameters, are primarily of importance for interpreting detailed core flood experiments since they do not scale in a simple way to the field and cannot therefore be used directly in the polymer field-scale simulations. 

Zhou, B. and Powell, A. (2006) Phase field simulations of liquid-liquid demixing during immersion precipitation of polymer membranes in 2D and 3D.J. Membr. Sci., 268 (2), 150-164. 

Additional Reading - Polymer Field Tests Additional Reading - Polymer Flood Simulation Models Additional Reading - Polymer Flow in Porous Media Additional Reading - Polymer Stability... 

Ken Green is a Senior Technologist for the Alberta Research Council. Ken is currently utilizing simulation programs to improve the design of polymer field applications. His work incorporates laboratory results to calibrate reservoir simulators for field-scale simulations. He has over 30 years of experience in laboratory studies for erihanced oU recovery. 

Sides, S.W., Kim, B.J., Kramer, E.J. and Fredrickson, G.H. (2005) Hybrid particle-field simulations of polymer nanocomposites. Physical Review Letters, 96, 250501. 

This is a new and potentially powerful method to simulate hydrodynamic phenomena. It is still a developing field which might have a big impact on polymer solutions simulations. An application to a polymer chain in solution (in two dimensions) is found in Ref. 78. A hybrid scheme between LGCA and MD was developed in Ref. 79. We feel however that the field has to mature further (and the relation of LCGA dynamics to the atomistic particle dynamics has to be further clarified) before they can be used as a standard tool in polymer dynamics. Once the relation between LGCA the local microscopic dynamics is established, one is tempted to expect a next quantum jump for the hydrodynamic simulations of complex fluids, such as polymers. 

These soft, partide-based models can be employed in conjunction with a variety of simulation tecimiques induding dissipative partide dynamics [100], Brownian dynamics [35], Monte Carlo simulations [39,41,105], and singlemean-field simulations [40-42]. These simulation tecimiques permit the investigation of the structure oflarge three-dimensional polymer systems with experimentally relevant X. 

Recent results of computer simulations and structure determinations are summarized in Sect. 4. Since Monte Carlo simulations will be reviewed in Sect. 4.1, only a short abstract of the recent state of research of this simulation method relevant to the chapter can be found in Sect. 4.1, along with recent developments in the polymer field theory which has made big advances recently. The recent state of molecular dynamics simulations (Sect. 4.2) is the main focus of Sect. 4. 

Field theoretical approaches have been successful in the area of polymer physics and physical chemistry [74, 77-79]. In particular, for mean field simulations great advances have been made in recent years, as can be seen in the extensive review of Ref. [74]. These advances led also to new developments in the field of PE solutions, e.g. in the simulation of the osmotic pressure of NaPSS solutions [74, 119]. 

Additional simulation development is planned to correct any variances between the observations and predictions, and also to apply the simulation to highly dynamic, non-isothermal, and non-Newtonian flows. Accordingly, it is believed that a coupled field simulation may be required that interleaves the bulk deformation of the flow according to the Navier-Stokes equations with the morphology development predicted by the Cahn-Hilliard equation. Accordingly, the simulation should support the process development of appropriate boundary and initial conditions to enable polymer self-assembly. 

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