Interpenetrating network, defined

Simultaneous Interpenetrating Networks. An interpenetrating polymer network, IPN, can be defined as a combination of two polymers in network form, at least one of which was polymerized or synthesized in the presence of the other (23). These networks are synthesized sequentially in time. A simultaneous interpenetrating network, SIN, is an IPN in which both networks are synthesized simultaneously in time, or both monomers or prepolymers mixed prior to gelation. The two polymerizations are independent and non-interfering in an SIN, so that grafting or internetwork crosslinking is minimized (23-26). 

Interpenetrating polymer networks are defined in their broadest sense as an intimate mixture of two or more pol)Mners in network form [1,2]. Ideally, they can be synthesized by either swelling the first crosslinked polymer with the second monomer and crosslinker, followed by in-situ polymerization of the second component (sequential IPN s) or by reacting a pair of monomers and crosslinkers at the same time through different, non-interfering reaction mechanisms, simultaneous interpenetrating networks, SIN s. In fact, many variations of these ideas exist in both the scientific and the patent literature. In any case, at least one of the two components must have a network structure, as an IPN prerequisite. ... 

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. 

Interpenetration is not limited to ordered crystalline materials. The polymeric interpenetrating networks are frequently believed to contain mechanically trapped polymer chainsJ" Inteipenetration has effects on the properties of the polymers when compared to their noninterpenetrating counterparts and is important in their applications. It is extremely difficult to define the exact topology of many of these systems, due to their polymeric nature, and the interested reader is recommended to read... 

An interpenetrating network (IPN) can be defined as a mixture of two crosslinked polymers when at least one of them is synthesized and (or) crosslinked with another [114]. The components that make up an IPN are thermodynamically incompatible and a transition region of two phases is formed in such a system. The whole complex of IPN properties is determined by the availability and features of this region. 

A fourth class of colloids often encountered is that of the network colloids. Such systems are difficult to define exactly because they consist of two interpenetrating networks, which make it hard to specify exactly which is the dispersed phase and which is the continuous phase. Classic examples of network colloids would be porous glass (air-glass), opal glass (solid-solid dispersion), and many gels. Practical examples of many of the colloids mentioned above are given in Table 10.2. 

An Interpenetrating network is defined as a blend in which one or more polymers are intimately cross-linked and one or more polymers are linear or branched. In this field, recent studies indicate that hyperbranched polymers (HBPs) may... 

In these two Ni-functionalized CNT materials, the Ni-molecular catalyst is located at the crossroads of the three interpenetrated networks allowing percolation of protons (the Nafion membrane), hydrogen (the pores in the gas diffusion layer), and electrons (the carbon fibers of the gas diffusion layer relayed by the conducting CNTs). In a way and even if it is not as well defined as in the protein, the catalyst environment in this membrane-electrode assembly reproduces that found in the active sites of hydrogenases buried into the polypeptidic framework but connected to the surfece of the protein via a gas diffusion channel, a network of hydrogen-bonded amino acids for proton transport and the array of electrontransferring iron-sulfur clusters. 

In this section, pure MOF systems as well as composites comprising MOF-encapsulated redox-active materials or interpenetrated networks are considered (see Interpenetration and Entanglement in Coordination Polymers and Patterning Techniques for Metal-Organic Frameworks). The reversibility and stability of their electrochemical response are discussed. Stability may be defined as a retained electrochemical response on repeated cycling, whereas electrochemical reversibility is linked to the concept of fast electron transfer at the... 

An interpenetrating polymer network, IPN, is defined as a combination of two polymers, both of which are crosslinked. Most IPN s are formed by synthesizing and/or crosslinking one network in the immediate presence of the other. Formed with covalent crosslinks, IPN s are thermoset, and do not flow or dissolve in ordinary solvents. Two main synthesis paths are illustrated in Figure 1 (a) polymer network I is synthesized, and monomer II plus crosslinker and activator are swollen in and polymerized in situ. This is called a sequential IPN (b) if both monomers or prepolymers are synthesized simultaneously by independent but non-interfering routes, the product is called a simultaneous interpenetrating network, SIN. ... 

An interpenetrating polymer network (IPN) is defined as a material comprising two or more networks which are at least partly interlaced on a molecular scale, hut not covalently bonded to each other. These networks caimot he separated unless chemical bonds are broken. Two possible methods exist for preparing them, as follows ... 

The 4,4 -bipy and bpe derivatives display a similar crystal structure to that of Cd(4,4 -bipy)2[Ag(CN)2]2 reported by Iwamoto et al. [89]. It consists of the interpenetration of two identical 3D networks. The knots of the networks are defined by the iron(II) and silver(I) atoms. Each iron(II) atom located on an inversion centre defines an elongated octahedron whose axial positions are occupied by the nitrogen atoms of two 4,4 -bipy ligands. In addition, each 4,4 -bipy ligand binds a silver atom so that it is three-coordinated. This is the reason why the [Ag(CN)2] group is bent (see Fig. 18). 

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