Molecular architecture theories

Next let us consider the differences in molecular architecture between polymers which exclusively display viscous flow and those which display a purely elastic response. To attribute the entire effect to molecular structure we assume the polymers are compared at the same temperature. Crosslinking between different chains is the structural feature responsible for elastic response in polymer samples. If the crosslinking is totally effective, we can regard the entire sample as one giant molecule, since the entire volume is permeated by a continuous network of chains. This result was anticipated in the discussion of the Bueche theory for chain entanglements in the last chapter, when we observed that viscosity would be infinite with entanglements if there were no slippage between chains. 

The first section of this book deals with current topics in network theory directed toward explaining the relationship between molecular architecture and macroscopic physical properties. The closely related questions of network formation and degradation are also discussed in this section. Deformation, fatigue, and fracture are discussed in the second section. The third section includes recent advances in cross-linking chemistry several chapters outline applications of new systems and detail the relationship between network structure and application properties. 

Symmetry The word symmetry means the same measure, which denotes harmony and beauty of the parts. It also plays a very important role in molecular architecture and material properties. The study of molecular symmetry is through a branch of group theory, that is, the point groups of rotations that leave one point... 

The orientation theory has made possible a great advance in our knowledge of molecular architecture, and Langmuir s work on this subject has been continued with great success by Adam. The experimental method was unchanged except for the substitution... 

Other reviews or updates have appeared during the past year. A comprehensive discussion of current electron-transfer theory, with emphasis on the more puzzling features, has been reported. Related aspects of bimolecular electron-transfer reactions have been discussed but in much less detail. Other authors have reviewed the special case in which light-induced electron transfer is followed by bond fragmentation or bond formation. In recent years there has been a virtual revolution in synthetic organic chemistry that has resulted in the construction of a wide range of exotic molecular architectures. Such systems have not... 

The fundamental principle of separation by SEC was described by Benoit and coworkers in 1967. They found an excellent correlation between the elution volume and a dynamically based molecular size, the hydrodynamic volume Vjj for a wide range of species and large-scale molecular architectures [9]. Their theory assumed a thermodynamic separation principle considering that the elution volume is independent of the flow rates. Recently, it has been proved that the radius of gyration is more appropriate than the hydrodynamic volume [10]. The radius of gyration is defined as the mean square distance away from the center of gravity [11]. Its mathematical definition is ... 

The reason why the random flight model has proved so popular theoretically stems from its simplicity, which offers hope for the development of analytic solutions. The problem can usually be cast in the form of a diffusionlike or a Schrodinger-wave-equation-like differential equation, the solutions of which are reasonably well explored. A tendency has developed in recent times to apply extremely sophisticated mathematical procedures to what are really very primitive models for polymer chains (see, e.g. Levine et al., 1978). Whether the ends merit the means in such instances cannot yet be assessed objectively. A strategy that might be more productive in terms of the development of a practical theory for steric stabilization is to aim for a simpler mathematical description of more complex models of polymer chains. It should also be borne in mind in developing ab initio theories that a simple model that may well suffice in polymer solution thermodynamics may be quite inadequate for the simulation of the conformational properties of polymers. Polymer solution thermodynamics seem to be relatively insensitive to molecular architecture per se whereas the conformation of a polymer chain is extremely sensitive to it. 

The model based on the lattice fluid SCF theory offers a means to calculate fundamental interfacial properties of microemulsions from pure component properties [25]. Because all of the relevant interfacial thermodynamic properties are calculated explicitly and the surfactant and oil molecular architectures are considered, the model is applicable to a wide range of microemulsion systems. The interfacial tension, bending moment, and interaction strength between the droplets can be calculated in a consistent manner and analyzed in terms of the detailed interfacial composition. The mechanism of the density effect on the natural curvature includes both an enthalpic and an entropic component. As density is decreased, the solvation of the surfactant tails is less favorable enthalpically, and the solvent is expelled from the interfacial region. Entropy also contributes to this oil expulsion due to the density difference between the interfacial region and the bulk. The oil expulsion and increased tail-tail interactions decrease the natural curvature. 

Model of Cell Membranes, Scl Am. 230(3), 26 (1974) see also the specialized journal, J. Membrane Biol. B. Lutenberg and L. Van Alphen, Molecular Architecture and Functioning of the Outer Membrane of Escherichia Coli and Other Gram-Negative Bacteria, Biochim. Biophys. Acta. IVl, 51-115 (1983) G. Cevc and D. Marsh, Properties of the Electrical Double Layer near the Interface Between a Charged Bilayer Membrane and Electrolyte Solution Experiment vs. Theory, J. Phys. Chem. 87, 376-379 (1983). 

Is the molecular architecture such as star-shaped polymers or combshaped polymers accounted for by the EOS theories ... 

Hohn C, Joanny JF, Kremer K, NetzRR, ReinekerP, Seidel C, Vilgis TA, Winkler RG (2004) Polyelectrolyte theory. In Polyelectrolytes with defined molecular architecture II, vol 166. Springer, Berlin, pp 67-111. doi 10.1007/B11349... 

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