Interpenetrating phases

Consequently, interpenetrating phase-separated D/A network composites, i.e. bulk heterojunction , would appear to be ideal photovoltaic materials [5]. By controlling the morphology of the phase separation into an interpenetrating network, one can achieve a high interfacial area within a bulk material. Since any point in the composite is within a few nanometers of a D/A interface, such a composite is a bulk D/A heterojunction material. If the network in a device is bicontinuous, as shown in Figure 15-26, the collection efficiency can be equally efficient. 

Fig. 7 Creep-resistance of the eutectic fiber consisting of interpenetrating phases of alpha-alumina and yttrium-aluminum-garnet (YAG) up to very high temperatures compared with other types of oxide fibers... 

These results demonstrated the usefulness of 13C NMR in studies of molecular structure and dynamics for the polymeric constituents of plant cuticle. Although these materials are insoluble and sometimes present as interpenetrating phases, CPMAS and spin relaxation techniques helped identify important carbon types and provided structural clues to the protective functions of cutin and suberin in terrestrial plants. 

A variety of catalysts work well in the typical hydrolyses reactions used, including acids, bases, and salts.29 Basic catalysts give precipitated phases that are generally well-defined particles, whereas the acidic catalysts give more poorly defined, diffuse particles.4,30 In some cases, particles are not formed at all, and bicontinuous (interpenetrating) phases result.17,31... 

Highly phase separated IPNs may very well have interpenetration only at the interface of the separate domains, and/or have interpenetrating phases. However, to the extent that interpenetration exists, adhesion between domains must still be affected and therefore, mechanical properties are altered as well. 

Davies model (see Equation 20.3 [20,21]) can be used for materials with co-continuous interpenetrating phases (as in interpenetrating networks), such as certain types of reaction injection molded elastomers [22], at all volume fractions. Equation 11.7 can then be used if (as is usually the case) one is interested in Young s modulus E rather than the shear modulus G. 

Craig B.D. 1997. Interpenetrating Phase Ceramic/Polymer Composite Coatings. [LFF] Daniels M. 1999. Colloidal Ceramic Coatings with Silane Coupling Agents. [LFF]... 

At the early development of polymer solar cells, a planar p-n junction structure represented the mainstream in mimicking conventional silicon-based solar cells. However, the obtained devices demonstrated poor photovoltaic performances due to the long distance between the exciton and junction interface and insufficient light absorption due to the thin light absorber. It was not until 1995 that the dilemma was overcome with the discovery of a novel bulk heterojunction in which donor and acceptor form interpenetrated phases. Poly[2-methoxy-5-(2 -ethylhexyloxy)-p-phenylene vinylene] was blended with Ceo or its derivatives to form the bulk heterojunction. A much improved power conversion efficiency of 2.9% was thus achieved under the illumination of 20 mW/cm. (Yu et al., 1995). The emergence of the donor/acceptor bulk-heterojunction structure had boosted the photovoltaic performances of polymer solar cells. Currently, a maximal power conversion efficiency of 10.6% had been reported on the basis of synthesizing appropriate polymer materials and designing a tandem structure (You et al., 2013). The detailed discussions are provided in Chapter 5. 

For convenience, we can regard an isotropic semicrystalline polymer as being made up of an isotropic polycrystalline phase and an isotropic amorphous phase, as shown in Fig. 6, which is purely diagrammatic (it shows the classical fringed micelle model for simplicity). From a geometrical standpoint, we cannot discriminate a priori between two continuous interpenetrating phases, a dispersion of a crystalline phase in an amorphous phase, or of an amorphous phase in a crystalline phase. The distinction may depend upon the volume fractions. 

Although materials with an interpenetrating phase microstmcture are relatively common in nature (forexample mammals bones andtmnks and branches in plants), they are still a novelty as synthetic materials. A complete review of composite materials with interpenetrating microstmctures was published by Clarke, emphasising on materials characterisation and models for property prediction [1]. 

Consequently, interpenetrating phase-separated D/A network composites, that is, bulk heterojunctions, appear to be ideal photovoltaic composites. The fundamental... 

Systems involving granular metal particles and polymers have been modeled in terms of mixtures of random voids and conductive particles. There is also an inverted random void model [15]. For CB in polymers, percolation is the process by which charge is transported through a system of interpenetrating phases. 

This, together with the above-mentioned phenomena such as crystallization or vitrification, may result in all kinds of particle morphologies, (co)continuous morphologies or interpenetration phase morphologies. The first results on epoxy and acrylic systems have already been published [58]. 

There is an instructive error in this paper which leads to an important safeguarding principle in making balances. Namely, when a sub-region of a process has been assumed to be uniform, balances that involve its properties must be taken over the whole of it. In simple situations there is little inclination to do otherwise, but in complex cases this may be the effect of a differential balance over another interpenetrating phase. See Aris for a full analysis [9]. We assume spherical particles of radius, R, and call the profile of concentration at time, a, c(r,a). If D is the diffusivity of the reactant and k the rate constant per unit volume of catalyst. 

---