Interconnected phases

The cl mg discovery process can be envisioned as four interconnected phases (see Figure 8.1). Generally, these are the acquisition of chemicals to be tested for biological activity, the determination of the activity of those chemicals on biological systems (pharmacodynamics), the formulation of the most active of these for therapeutic testing in humans (pharmaceutics), and the determination of adequate delivery of the active drug to diseased tissues (pharmacokinetics). Each of these collections of processes is interconnected with the others and failure in any one of them can halt the development process. It is worth considering each process separately, as well as the relationships between them. 

Schematic depiction of the structural evolution of polymer electrolyte membranes. The primary chemical structure of the Nafion-type ionomer on the left with hydrophobic backbone, side chains, and acid head groups evolves into polymeric aggregates with complex interfacial structure (middle). Randomly interconnected phases of these aggregates and water-filled voids between them form the heterogeneous membrane morphology at the macroscopic scale (right).

In general, we expect valuable insights for the advanced design of catalyst layers from understanding the microstructure of interconnected phases of... 

Similar arguments explaining the phase separation were employed by Chou et al. [44]. The dynamics of phase separation was observed using an optical microscope during the course of polyurethane-unsaturated polyester IPN formation at different temperature. Chou et al. suggested that an interconnected phase formed through the spinodal decomposition mechanism developed quickly and was followed by the coalescence of the periodic phase to form a droplet/matrix type of morphology. The secondary phase separation occurred within both the droplet and the matrix phases. Chou et al. did not explain, however, why secondary phase separation occurred. 

Several borosilicate glass compositions exhibit immiscibil-ity they separate into two interconnecting phases, one rich in... 

Formation of continuous interconnected phases if the proportional amounts of the two separating phases approach unity. This type of separation is called spinodal decomposition and takes place spontaneously without any energy barrier which would otherwise have to be overcome during nucleation. 

In retrospect, the pathway to discovery was not direct. We were looking for improved vulcanizable rubbers. Instead we discovered rubbers that did not require vulcanization (Figure 2). However, the events listed in Table II suggest that one could have found a more direct pathway to the discovery of the importance of two interconnecting phases in polymers. 

From a general point of view, the challenge in the case of reaction-induced phase separation is to create new morphologies (particle sizes at the nanometer scale, transparent two-phases materials, interconnected phases, etc.) and to control the properties of the interface (adhesion, and also the internal stress concentration). For size adjustment, it is possible to superimpose a thermal quench to the reaction-induced phase separation [144], In the case of thermoplastic blends the interfaces or interphases can be modified and modelled by the use of block copolymers, especially triblock terpolymers ABC [145]. A similar systematic approach can be developed in thermoset blends and the results are expected to be different to those obtained by the use of functionalized modifiers [71,138, 146-148]. 

Phase separation temperature goes down, goes up. Faster cure gives smaller particles. Interconnected phase separated globules of the PES. 

In this approach, all the materials are treated as separated (but interconnected) phases (e g. catalyst electrochemistry and carbon corrosion.All the chemical and electrochemical processes are modelled as series-parallel elemerrtary... 

A catalyst ink is prepared by mixing the catalyst powder that consists of primary Pt/C particles in dispersion media that are mixtures of water, alcohols, or other organic compounds (Xie et al., 2008). lonomer is added until a desired ionomer-to-carbon mass ratio is reached. For a review of catalyst layer fabrication approaches, see Chapter 19 in Zhang (2008). The added ionomer self-assembles into a separate interconnected phase in the pore space, primarily in secondary pores. The final CL structure depends on materials used, ink composition, dispersion medium, fabrication conditions, and the protocol of MEA fabrication and drying. 

Figure 8-2. Schematic examples of two-electron density systems, (a) A set of isolated objects with a constant electron density embedded in a homogeneous matrix, (b) Continuous and interconnected phases, both with a constant electron density.

Mechanical properties of IPNs will differ, depending on the mechanism of the phase separation. For the case of nucleation, the traditional models may be used, which have been discussed in Chapter 4 for filled polymers. These models allow one to predict the properties of two-phased systems of the matrix-inclusion type. For IPNs which are decomposed according to the spinodal mechanism, the appearance of two interconnected phases and dual-phase continuity should be taken as a basis for calculations. 

Experimental and microstructural studies of granitic rocks demonstrate that feldpars are stronger than quartz [286]. By contrast, plagioclase feldspar becomes a weak and interconnected phase controlling the rheology of more mafic gabbroic rocks [263], which are common in the lower continental crust and oceanic crust. 

Without disputing the general tendency of papers [25, 26], in which it is assumed that yield stress is defined by thermal stability of crystallites, it is necessary to note the narrowness of this approach. A semi-crystalline polymer represents a complex dissipative system, consisting of two interconnected phases (amorphous and crystalline) and interfacial regions between them [27]. Therefore it is clear even intuitively that the structural changes in amorphous and interfacial regions cannot help influencing the behaviour and state of a crystalline phase. The experimental confirmation of such... 

The presence of co-continuous phase morphology, which consists of at least two coexisting, continuous, and interconnected phases throughout the whole blend volume, is the other important superstructural characteristic... 

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