Solid mesoscale

Mesoscale simulations model a material as a collection of units, called beads. Each bead might represent a substructure, molecule, monomer, micelle, micro-crystalline domain, solid particle, or an arbitrary region of a fluid. Multiple beads might be connected, typically by a harmonic potential, in order to model a polymer. A simulation is then conducted in which there is an interaction potential between beads and sometimes dynamical equations of motion. This is very hard to do with extremely large molecular dynamics calculations because they would have to be very accurate to correctly reflect the small free energy differences between microstates. There are algorithms for determining an appropriate bead size from molecular dynamics and Monte Carlo simulations. 

Underlying all continuum and mesoscale descriptions of shock-wave compression of solids is the microscale. Physical processes on the microscale control observed dynamic material behavior in subtle ways sometimes in ways that do not fit nicely with simple preconceived macroscale ideas. The repeated cycle of experiment and theory slowly reveals the micromechanical nature of the shock-compression process. 

Yabu, H. and Shimomura, M. (2005) Preparation of self-organized mesoscale polymer patterns on a solid substrate continuous pattern formation from a receding meniscus. Adv. Func. Mater,... 

Fujita S Inagaki S, Self-organization of organosilica solids with molecular-scale and mesoscale periodicities, Chem. Mater., 2008, 20, 891-908. 

Hoshino K, Inui M, Kitamura T, Kokado H. Fixation of dinitrogen to a mesoscale solid salt using a titanium oxide/conducting polymer systems. Angew Chem 2000 112 2558-61. 

Figure 36. Defect concentration and conductance effects for three different thicknesses Li L2 Lj. The mesoscale effect on defect concentration (l.h.s.) discussed in the text, when L < 4J, is also mirrored in the dependence of the conductance on thickness (r.h.s.). If the boundary layers overlap , the interfacial effect previously hidden in the intercept is now resolved. It is presupposed that surface concentration and Debye length do not depend on L. (Both can be violated, c , at sufficiently small L because of interaction effects and exhaustibility of bulk concentrations.)36 94 (Reprinted from J. Maier, Defect chemistry and ion transport in nanostructured materials. Part II. Aspects of nanoionics. Solid State Ionics, 157, 327-334. Copyright 2003 with permission from Elsevier.)...

The leitmotifs of these devices include bespoke dye sensitisers, space-quantised nanoscale structures that enable hot carrier or multiple exciton generation, molecular and solid-state junction architectures that lead to efficient exciton dissociation and charge separation, and charge collection by percolation through porous or mesoscale phases. Another common theme underlying the devices discussed in this book is the... 

The mesoscale models for momentum transfer between phases differ quite substantially depending on the multiphase system under investigation, and different semi-empirical relationships have been developed for different systems. Since the nature of the disperse phase is particularly important, the available mesoscale models are generally divided into those valid for fluid-fluid and those valid for fluid-solid systems. The main difference is that in fluid-fluid systems the elements of the disperse phase are deformable particles (i.e. bubbles or droplets), whereas in fluid-solid systems the disperse phase is constituted by particles of constant shape. Typical fluid-fluid systems for which the mesoscale models reported below apply are gas-liquid, liquid-liquid, and liquid-gas systems. The mesoscale models reported for fluid-solid systems are valid both for gas-solid and for liquid-solid systems. As a general rule, the mesoscale model for Afp should be derived starting from a single-particle momentum balance ... 

The linear viscoelastic properties in the melt state of highly grafted polymers on spherical silica nanoparticles are probed using linear dynamic oscillatory measurements and linear stress relaxation measurements. While the pure silica tethered polymer nanocomposite exhibits solid-like response, the addition of a matched molecular weight free matrix homopolymer chains to this hybrid material, initially lowers the modulus and later changes the viscoelastic response to that of a liquid. These results are consistent with the breakdown of the ordered mesoscale structure, characteristic of the pure hybrid and the high hybrid concentration blends, by the addition of homopolymers with matched molecular weights. 

C.H. Tan, A.R. Inigo, J.H. Hsu, W. Fann, and P.K. Wei, Mesoscale structures in luminescent conjugated polymer thin films studied by near-field scanning optical microscopy. J. Phys. Chem. Solids, 62, 1643 (2001). 

Since nanoparticles in PNC are orders of magnitude smaller than conventional reinforcements, the models developed for composites are not applicable to nanocomposites. However, development of a universal model for PNC is challenging since the shape, size, and dispersion of the nanoparticles vary widely from one system to another. On the one hand, exfoliated clay provides vast surface areas of solid particles (ca. 800 m /g) with a large aspect ratio that adsorb and solidify a substantial amount of the matrix polymer, but on the other hand, the mesoscale intercalated clay stacks have a much smaller specific surface area and small aspect ratio. However, in both these cases the particle-particle and particle-matrix interactions are much more important than in conventional composites, affecting the rheological and mechanical behavior. Thus, the PNC models must include the thermodynamic interactions, often neglected for standard composites. 

This polymerization process can be separated into three different levels as proposed by Ray [22]. First this is the microscale level, modeling all processes at the surface and inside the growing polymer particle. The next level is the mesoscale level, describing all mass and heat transfer processes inside the three-phase slurry containing gas bubbles, hydrocarbon diluent with the dissolved aluminumalkyl compound, and the solid growing polymer particles loaded with the active sites. Finally, there is the macroscale level comprising the polymerization vessel as a whole, with sensors to control this slurry polymerization process. These three levels are shown in Fig. 4. 

Liquid crystalline mesophases can also be prepared in non-aqueous solution. Using ethanolic solutions of non-ionic block copolymers as a medium, Zhao et for example, have developed a route by which mesoporous metal phosphates and borates can readily be prepared. A mixture of the metal alkoxide and the acidic chloride is used to give a complex in ethanolic solution. This acid-base pair reacts in one component of the liquid crystalline assembly to give a mesophase solid of uniform composition. Evaporation of the ethanol leaves the mesostructure. This appears to be one of the most promising routes to the formation of non-silica mesoporous solids. Many reports of these solids have appeared, particularly of metal oxides such as titanium dioxide, but loss of ordering on the mesoscale frequently occurs upon template removal. The route of Sanchez, which involves the use of titanate precursor species in the sol-gel, is a promising approach to stable mesostructured titania that retains its porosity. 

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