Non-mechanical dynamic properties

The temperature dependence of the Payne effect has been studied by Payne and other authors [28, 32, 47]. With increasing temperature an Arrhe-nius-like drop of the moduli is found if the deformation amplitude is kept constant. Beside this effect, the impact of filler surface characteristics in the non-linear dynamic properties of filler reinforced rubbers has been discussed in a review of Wang [47], where basic theoretical interpretations and modeling is presented. The Payne effect has also been investigated in composites containing polymeric model fillers, like microgels of different particle size and surface chemistry, which could provide some more insight into the fundamental mechanisms of rubber reinforcement by colloidal fillers [48, 49]. 

Let us return to the problem of solving the response of the quantum mechanical system to an external electric field. The zeroth-order wave function of the quantum mechanical system is obtained by use of any of the standard approximate methods in quantum chemistry and the coupling to the field is described by the electtic dipole operator. There exist a number of ways to determine the response functions, some of which differ in formulation only, whereas others will be inherently different. We will give a short review of the characteristics of tire most common formulations used for the calculation of molecular polarizabilities and hyperpolarizabilities. The survey begins with the assumption that the external perturbing fields arc non-oscillatory, in which case we may determine molecular properties at zero frequencies, and then continues with the general situation of time-dependent fields and dynamic properties. 

Non-linear viscoelastic properties were observed for fumed silica-poly(vinyl acetate) (PVAc) composites, with varying PVAc molar mass and including a PVAc copolymer with vinyl alcohol. Dynamic mechanical moduli were measured at low strains and found to decrease with strain depending on surface treatment of the silica. The loss modulus decreased significantly with filler surface treatment and more so with lower molar mass polymer. Copolymers with vinyl alcohol presumably increased interactions with silica and decreased non-linearity. Percolation network formation or agglomeration by silica were less important than silica-polymer interactions. Silica-polymer interactions were proposed to form trapped entanglements. The reinforcement and nonlinear viscoelastic characteristics of PVAc and its vinyl alcohol copolymer were similar to observations of the Payne effect in filled elastomers, characteristic of conformations and constraints of macromolecules. ... 

The most basic approach to carry out MD simulations for larger systems is to use classical force fields. A variety of different force fields for molecular mechanics (MM) simulations has been developed,which are mainly intended to describe the non-reactive dynamics of large systems. In particular in the field of biochemistry force fields play an essential role to study the complex properties of large biomolecules. However, classical force fields require the specification of the connectivity of the atoms. Therefore, they are not able to describe chemical reactions, i.e., the making and breaking of bonds. To describe reactions, they can be combined with quantum mechanical (QM) methods in so-called QM/MM simulations. In recent years also reactive force fields , e.g. ReaxFF, have been introduced, which overcome this limitation. However, these reactive force fields are typically highly adapted to specific systems by analytic terms customized to describe e.g. certain bonding situations, and only a few applications have been reported so far. 

Fig. 5 Dynamic modification of the mechanical and optical properties of two metallodynamers by recombination of their components via ligand exchange coordinatimt dynamics. Top Mechanical change involving blending of a hard film and a gum into a soft film. Bottom Optical change produced by blending of the two non-emissive dynamers into a material presenting a yellowish emission (see [54] for more details)...

Modem first principles computational methodologies, such as those based on Density Functional Theory (DFT) and its Time Dependent extension (TDDFT), provide the theoretical/computational framework to describe most of the desired properties of the individual dye/semiconductor/electrolyte systems and of their relevant interfaces. The information extracted from these calculations constitutes the basis for the explicit simulation of photo-induced electron transfer by means of quantum or non-adiabatic dynamics. The dynamics introduces a further degree of complexity in the simulation, due to the simultaneous description of the coupled nuclear/electronic problem. Various combinations of electronic stmcture/ excited states and nuclear dynamics descriptions have been applied to dye-sensitized interfaces [54—57]. In most cases these approaches rely either on semi-empirical Hamiltonians [58, 59] or on the time-dependent propagation of single particle DFT orbitals [60, 61], with the nuclear dynamics being described within mixed quantum-classical [54, 55, 59, 60] or fuUy quantum mechanical approaches [61]. Real time propagation of the TDDFT excited states [62] has... 

The need for an efficient, compact and environmentally friendly energy storage source has led to the evolution of all solid battery systems that utilize electrolytes consisting of solid or at least non-leaking polymer materials. Properties of these are often compromises achieved by optimization of mechanical, dynamic and compatibility issues with addition of economic and environmental impact aspects. 

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