Morphology bicontinuous

It is well known that block copolymers and graft copolymers composed of incompatible sequences form the self-assemblies (the microphase separations). These morphologies of the microphase separation are governed by Molau s law [1] in the solid state. Nowadays, not only the three basic morphologies but also novel morphologies, such as ordered bicontinuous double diamond structure, are reported [2-6]. The applications of the microphase separation are also investigated [7-12]. As one of the applications of the microphase separation of AB diblock copolymers, it is possible to synthesize coreshell type polymer microspheres upon crosslinking the spherical microdomains [13-16]. 

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. 

The mechanism of formation of morphology structures in iPP-E-plastomers blends via shear-dependent mixing and demixing was investigated by optical microscopy and electron microscopy. A single-phase stmcture is formed under high shear condition in injection machine after injection, namely under zero-shear environments, spinodal decomposition proceeds and leads to the formation of a bicontinuous phase stmcture. The velocity of spinodal decomposition and the phase separation depend on the molecular stmcture of iPP and E-plastomer components. 

In what follows we will discuss systems with internal surfaces, ordered surfaces, topological transformations, and dynamical scaling. In Section II we shall show specific examples of mesoscopic systems with special attention devoted to the surfaces in the system—that is, periodic surfaces in surfactant systems, periodic surfaces in diblock copolymers, bicontinuous disordered interfaces in spinodally decomposing blends, ordered charge density wave patterns in electron liquids, and dissipative structures in reaction-diffusion systems. In Section III we will present the detailed theory of morphological measures the Euler characteristic, the Gaussian and mean curvatures, and so on. In fact, Sections II and III can be read independently because Section II shows specific models while Section III is devoted to the numerical and analytical computations of the surface characteristics. In a sense, Section III is robust that is, the methods presented in Section III apply to a variety of systems, not only the systems shown as examples in Section II. Brief conclusions are presented in Section IV. 

The topological transformations in an incompatible blend can be described by the dynamic phase diagram that is usually determined experimentally at a constant shear rate. For equal viscosities, a bicontinuous morphology is observed within a broad interval of the volume fractions. When the viscosity ratio increases, the bicontinuous region of the phase diagram shrinks. At large viscosity ratios, the droplets of a more viscous component in a continuous matrix of a less viscous component are observed practically for all allowed geometrically volume fractions. 

Figure 18. Different stages of the spinodal decomposition in an asymmetric mixture (0 = 0.5) t is the dimensionless time. The Euler characteristic is initially negative, which indicates that morphology is bicontinuous. After a certain time the Euler characteristic becomes positive, which indicates that the transition to dispersed morphology occurred. For a dispersed morphology the Euler characteristic equals twice the droplet number.

Figure 40. Time evolution of the Euler characteristic density for different average volume fractions, 4)0 — 0.5, 0.4, 0.375, 0.36, 0.35, and 0.3, quenched from the homogeneous state binary mixture. The negative Euler characteristic corresponds to the bicontinuous morphology, while the... 

Figure 41. The percolation threshold determination for polymer blends undergoing the phase separation. Minority phase volume fraction, fm, is plotted versus the Euler characteristic density for several simulation runs at different quench conditions, /meq- = 0.225,..., 0.5. The bicontinuous morphology (%Euier < 0) has not been observed for fm < 0.29, nor has the droplet morphology (/(Euler > 0) been observed for/m > 0.31. This observation suggests that the percolation occurs at fm = 0.3 0.01.

Figure 3.20 Model for the morphology formation during curing of thermoplastic/thermoset blend via (a) NG only (b) NG followed by SD dispersed thermoplastic rich phase (c) NG followed by SD bicontinuous, and (d) NG followed by SD dispersed thermoset rich phase (e) SD only...

Fig. 6.11 TEM images showing a sequence of morphologies on increasing PS homopolymer (M = 5.9kgmor ) concentration (wt%) in blends with a PS-PI diblock (Mr = 48.7kgmol-1,/PS = 0.51) (Winey et al. 1991c). The blends were annealed at 125 °C. (a) 10% PS, lamellae, (b) 30% PS, bicontinuous cubic, (c) 50% PS, hexagonal-packed cylinders, (d) 70% PS, cubic-packed spheres.

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