Subject Structure-property relationship

The structure/property relationships in materials subjected to shock-wave deformation is physically very difficult to conduct and complex to interpret due to the dynamic nature of the shock process and the very short time of the test. Due to these imposed constraints, most real-time shock-process measurements are limited to studying the interactions of the transmitted waves arrival at the free surface. To augment these in situ wave-profile measurements, shock-recovery techniques were developed in the late 1950s to assess experimentally the residual effects of shock-wave compression on materials. The object of soft-recovery experiments is to examine the terminal structure/property relationships of a material that has been subjected to a known uniaxial shock history, then returned to an ambient pressure... 

To illustrate the effect of radial release interactions on the structure/ property relationships in shock-loaded materials, experiments were conducted on copper shock loaded using several shock-recovery designs that yielded differences in es but all having been subjected to a 10 GPa, 1 fis pulse duration, shock process [13]. Compression specimens were sectioned from these soft recovery samples to measure the reload yield behavior, and examined in the transmission electron microscope (TEM) to study the substructure evolution. The substructure and yield strength of the bulk shock-loaded copper samples were found to depend on the amount of e, in the shock-recovered sample at a constant peak pressure and pulse duration. In Fig. 6.8 the quasi-static reload yield strength of the 10 GPa shock-loaded copper is observed to increase with increasing residual sample strain. 

The electronic structure of fluorenes and the development of their linear and nonlinear optical structure-property relationships have been the subject of intense investigation [20-22,25,30,31]. Important parameters that determine optical properties of the molecules are the magnitude and alignment of the electronic transition dipole moments [30,31]. These parameters can be obtained from ESA and absorption anisotropy spectra [32,33] using the same pump-probe laser techniques described above (see Fig. 9). A comprehensive theoretical analysis of a two beam (piunp and probe) laser experiment was performed [34], where a general case of induced saturated absorption anisotropy was considered. From this work, measurement of the absorption anisotropy of molecules in an isotropic ensemble facilitates the determination of the angle between the So Si (pump) and Si S (probe) transitions. The excited state absorption anisotropy, rabs> is expressed as [13] ... 

These models require accurate data on physico-chemical properties of organic substances, which is the subject of Dr. Mackay s other interest, namely their measurement and correlation. This includes the compilation and critical review of these properties and their quantitative structure property relationships. He is co-author of the five-volume Illustrated Handbook of Physical Chemical Properties and Environmental Fate of Organic Chemicals, which documents data reported in the literature, and is also available in CD-ROM format from CRC Press. Dr. Mackay s hope is that a combination of the information reported in these handbooks, and the estimated data as described in the present volume, can provide a sound basis for assessment of the large and growing number of chemical substances of environmental concern. 

The structure of a chemical is responsible for the presence and magnitude of its properties. The properties can be energy levels and their derivatives, as well as physicochemical, or biological, properties. To avoid discrimination between the different properties (which are the subject of detailed consideration in Chapters 3, 4, and 6) in the context of quantitative relationships between structural descriptors (i.e., topological indices [TIs]) and various properties, we will use the broader abbreviation QSPR (Quantitative Structure-Property Relationship). 

Currently, there is growing interest in polymers the frameworks of which are constructed from the Group 14 elements silicon, germanium and tin. Several reviews on polysilanes have appeared in the literature . In the first section of this article we focus on recent developments in the chemistry of polygermanes and polystannanes. The chemistry and structure-property relationship of oligostannanes and low molecular weight polystannanes was the subject of earlier reviews . ... 

The second appendix, by Dr. Donald B. Boyd, is an updated compendium of software for molecular modeling, computational chemistry, de novo molecular design, quantitative structure-property relationships, synthesis planning, and other facets of computers helping molecular science. This is one of the most current and most complete compilations anywhere. Appendix 2 provides addresses, telephone numbers, and electronic mailing addresses of suppliers of software. Combined with the subject index of this volume, it is possible to... 

The search for quantitative structure-property relationships for the control and prediction of the mechanical behaviour of polymers has occupied a central role in the development of polymer science and engineering. Mechanical performance factors such as creep resistance, fatigue life, toughness and the stability of properties with time, stress and temperature have become subjects of major activity. Within this context microhardness emerges as a property which is sensitive to structural changes. 

Even less is known about ionomer/plasticizer interactions on a molecular level. A variety of scattering and spectroscopic techniques that can probe this level have been mentioned, but they have been applied primarily to the specific case of water in ionomers, and in particular to hjdrated perfluorinated ionomers. At the least, these studies demonstrate the powerful potential of the techniques to contribute to a more complete understanding of structure-property relationships in plasticizer/ionomer systems. For e.xample, to return to the question of the effect of nonpolar plasticizers on the ionic domains how can the decrease in the ionic transition temperature be reconciled with the apparently minimal effect on the SAXS ionomer peaks and with the ESR studies that indicate (not surprisingly) tiiat these plasticizers have essentially no influence on the local structure of the ions Is it due to their association with the hydrocai bon component of the large aggregates or clusters Or if these entities do not exist, as some researchers postulate, what is the interaction between the nonpolar plasticizer, the hydrocarbon component and the ionic domains These questions are, of course, intimately related to the understanding of ionomer microstructure even in the absence of plasticizer. The interpretation of SAXS data in particular is subject to the choice of model used. 

This brief historical summary of Permasep permeator developments introduces the subject of structure-property relationships for membranes from aromatic polyamides and derivatives. 

The main contribution to the ability to predict the mechanical properties of polymers, by the work presented in this book, is then the new set of quantitative structure-property relationships, not subject to the limitations traditionally imposed by the need for group contributions, for the many input parameters entering the correlations developed for the mechanical properties. This development has allowed the prediction of the mechanical properties of many novel polymers whose mechanical properties could not be estimated previously. 

There are a number of considerations that must be addressed when formulating quantitative 13c NMR procedures - these include solvent effects, spectral overlap, line widths, dynamic and nuclear Overhauser effects and detailed assignments. The steps required to develop sound quantitative methods will be the subject of this chapter. It is imperative that excellent quantitative methods be established so that NMR can be utilized in studies of polymer structure-property relationships. Polymer molecular structure needs to be related to the incipient solid state structure and ultimately to observed solid state physical properties such as density, flexural moduli, environmental stress cracking behavior, to name a few. 

When we progress from the foregoing qualitative discussion of structure-property relationships to the quantitative specification of mechanical properties, we enter a jungle that has been only partially explored. The most convenient point of departure into this large and complex subject is provided by the topic of "linear viscoelasticity." Linear viscoelasticity represents a relatively simple extension of classical (small-strain) theory of elasticity. In situations where linear viscoelasticity applies, the mechanical properties can be determined from a few experiments and can be specified in any of several equivalent formulations (11). 

DMA is a very useful thermoanalytical tool for studying the structure-property relationship versus performance of polymeric materials. The important information concerning relaxation transitions occurring on a molecular scale can be derived by subjecting polymers to a small amplitude cyclic deformation. Data obtained over a broad temperature range help to understand the influence of one polymer on the properties of another polymeric component... 

This contribution aims to briefly review studies on the exploration of structure-property relationships of metal nanoparticles with a specific focus on the eflects of particle size and shape. A number of earher, more specific, and detailed reviews provide an ample opportunity for a reader to deepen understanding of this subject [8-12]. Here, the focus is to review selected recent papers, along with a limited number of historically important papers that put more recent findings into perspective. 

This chapter provides a more in-depth survey of the use of isocyanates and polyurethanes as structural adhesives, including their virtues as well as their present limitations. In order to familiarize the reader with polyurethanes, a general discussion of their chemistry and structure-property relationships will first be presented. More detailed reviews of this subject have been published in a number of standard texts. ... 

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