Open networks

It is somewhat difficult conceptually to explain the recoverable high elasticity of these materials in terms of flexible polymer chains cross-linked into an open network structure as commonly envisaged for conventionally vulcanised rubbers. It is probably better to consider the deformation behaviour on a macro, rather than molecular, scale. One such model would envisage a three-dimensional mesh of polypropylene with elastomeric domains embedded within. On application of a stress both the open network of the hard phase and the elastomeric domains will be capable of deformation. On release of the stress, the cross-linked rubbery domains will try to recover their original shape and hence result in recovery from deformation of the blended object. 

In some instances it is desired to produce a more open network from epoxide resins that have been acid-cured. This may be achieved by the oligoesterdi-carboxylic acids of general structure... 

Fig. 3.18 Schematic outline and ideal band diagram of an extremely thin absorber solar cell. The n-Ti02 crystallites are clustered together to form a relatively open, network-like morphology, accommodating a thin layer of CdTe absorber, with p-ZnTe at the back contact. (Reprinted from [270], Copyright 2009, with permission from Elsevier)...

Although intermediate filaments are not universally associated with the cytoskeleton, neutrophils possess intermediate filaments of the vimentin type. Vimentin is a rod-shaped molecule of relative molecular mass 57 kDa that readily polymerises under physiological conditions to produce stable filaments 10-12 nm in diameter. Intermediate filaments are more robust than microfilaments and microtubules, and in neutrophils they form an open network of single filaments in the perinuclear space. 

Open network formed by the removal of all swelling agents from a gel. 

The somewhat open network structure of solid water determines that the density of ice at 0 °C is 916.7 kg m 3. That of liquid water at 0 °C is 999.8 kg m 3 so solid ice floats on water, a fact noticed eventually by the captain of the Titanic1. In liquid water at 0 CC there is still considerable... 

Blends of polyphenylenevinylene with water-soluble polymers have been prepared by mixing solutions of the sulfonium precursor with polyethyleneoxide, hydroxy-propylcellulose and polyvinylmethylether317). Polyethyleneoxide forms spherulites which impose a spherulitic texture to the polyphenylenevinylene that is retained after transformation. As a result of this open network, high conductivities are reached at only 10% conducting polymer. 

Homogeneous nonideal, e.g. open networks, obtained from the same chemistry as the previous ones. These networks contain dangling chains as a result of incomplete cure, nonstoichiometric composition, or presence of monofunctional monomers. 

Inhomogeneous open networks characterized by spatial fluctuations of the crosslink density (nodular/globular morphologies, microgels, see Chapter 7). 

This is apparent in the case of industrial systems [6]0, which are making increasing use of the capabilities offered by open networks for remotely accessing sensors and actuators for their operation and maintenance. Control and supervision systems are typically embedded in other critical infrastructures electric power, potable water, oil and gas, railways, etc. The potential advantages from the economic and functional viewpoints are unquestionable less often studied are the risks that these connections might... 

The tetrahedral open network is a specific characteristic not only of water and silica but also of covalent systems such as Si and Ge (group IV semiconductors) [254, 255], These substances share many characteristics with water, such as... 

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