Interpenetrating networks example

Another area of recent interest is covulcanization in block copolymers, thermoplastic rubbers, and elasto-plastic blends by developing an interpenetrating network (IPN). A classical example for IPN formation is in polyurethane elastomer blended acrylic copolymers [7]. 

In the simultaneous interpenetrating networks (SIN), the two reactions are run simultaneously. This reaction will be emphasized in the present paper. One reaction, for example, can be a polyesterification or a polyurethane stepwise reaction, while the other is an addition reaction using styrene to make polystyrene via free radical chemistry. 

Network colloids have two phases forming an interpenetrating network, for example, a polymer matrix. 

Figure 6.57 Ten connectivity patterns for a diphasic solid. Each phase has zero-, one-, two-, or three-dimensional connectivity to itself. In the 3-1 composite, for example, the shaded phase is three-dimensionally connected and the unshaded phase is one-dimensionally connected. Arrows are used to indicate the connected directions. Two views of the 3-3 and 3-2 patterns are given because the two interpenetrating networks are difficult to visualize on paper. The views are related by 90° counterclockwise rotation about Z. (After Newnham Cross, 1981.)...

Some general points about interpenetrating networks can be illustrated by the example of Zn(CN)2, which was structurally characterized over half a century ago [3]. It consists of two independent diamond-like nets with the 66-a topology, in which zinc provides the tetrahedral nodes and cyanide provides linear connections between nodes. These two equivalent but independent nets interpenetrate as shown in Figure 4, such that the nodes of one net are located at the centers of the... 

These reactions can also be used to form networks that interpenetrate,18,237,261-267 as illustrated in Figure 4.10.237 For example, one network could be formed by a condensation end-linking of hydroxyl-terminated short chains and the other by a simultaneous but independent addition end-linking of vinyl-terminated long chains. Interpenetrating networks are of interest because they can be unusually tough, and could have unusual dynamic mechanical properties. 

Supramolecular isomerism Supramolecular isomerism has been defined by Zaworotko64 as the existence of more than one type of network superstructure for the same molecular building blocks, and hence he adds that it is therefore related to structural isomerism at the molecular level. In cases where the molecular building blocks are capable of forming more than one type of supramolecular synthon then supramolecular isomerism is identical to polymorphism. Zaworotko defines another kind of supramolecular isomerism, however, in which the same building blocks exhibit different network architectures or superstructures. We will see examples of this phenomenon in chapter 9, particularly regarding interpenetrated networks. 

Continuity can also be reached by polymerizing one of the components within the other. In such a case the blend is called an IPN, an interpenetrating network it is, in most cases formed by a thermoset in a thermoplastic polymer. An example is a compound built-up from 50% of a thermoplast (polycarbonate or polysulphone), and 50% of a cross-linked polymer on the basis of dicyanate bisphenol-A. The skeleton... 

In other cases, it may be important to indicate that the mixing or reactions were carried out simultaneously. This will be indicated, where necessary, by brackets. See example in Equation 18. This indicates a simultaneous interpenetrating network, where Cu was formed by one... 

IPN s and related materials) in fact) have a long history. For example) IPN s were first synthesized to produce smooth sheets of bulk polymerized homopolymers (11), IPN s were next used as solution polymerized ion exchange resins. (12) 13) Further development of IPN s included the syntheses oT interpenetrating elastomer networks (lEN s) and simultaneous interpenetrating networks (SIN s) (14). lEN s consist of a mixture of different emulsion polymerized elastomers which are both crosslinked after coagulation. SIN s are formed by the simultaneous polymerization of mixed monomers by two noninterfering reactions (3 ) 16). 

In addition, aUcynyl groups not only inhibit thermally inducted depolymerization, they can also be functionalized by, for example, hydroboration, hydro-silylation, or by attaching transition metal complex fragments. Accordingly, nnits provide an access to multicomponent ceramics. For example, Corriu et al. reported that [SiR2C=C-C=C] are precursors with interpenetrating networks to... 

The plot of i as a function of Xe exhibits a maximum in the electroactive fraction i /(i Xm) of catalyst particles (normalized to the metal content). For the specified percolation parameters of the layer, the catalyst utilization corresponding to this maximum is 42%, as obtained at = 0.5 (and Xrn = 0.3). This example illustrates the limitations imposed on the catalyst utilization by the percolation properties of the interpenetrating networks. 

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