Lamella phase

Fig. 1 Phase diagram of self-assembled structures in AB diblock copolymer melt, predicted by self-consistent mean field theory [31] and confirmed experimentally [33]. The MesoDyn simulations [34, 35] demonstrate morphologies that are predicted theoretically and observed experimentally in thin films of cylinder-forming block copolymers under surface fields or thickness constraints dis disordered phase with no distinct morphology, C perpendicular-oriented and Cy parallel-oriented cylinders, L lamella, PS polystyrene, PL hexagonally perforated lamella phase. Dots with related labels within the areal of the cylinder phase indicate the bulk parameters of the model AB and ABA block copolymers discussed in this work (Table 1). Reprinted from [36], with permission. Copyright 2008 American Chemical Society...

As shown in Figure 32, the sector column phase can also be considered as the distortion of the vertical lamellae phase in the flat plates system, which is a counterpart to the above parallel lamellae. With the assumption of the repeated number of basic A-B unit in the cylinder, and the interval angle of basic unit, 6 = 2jt/M, M is the number of sectors, the interfacial contribution per copolymer chain can be expressed as ... 

Ohtsuru et al. (25) have recently investigated the behavior of phosphatidylcholine in a model system that simulated soy milk. They used spin-labelled phosphatidylcholine (PC ) synthesized from egg lysolecithin and 12-nitroxide stearic acid anhydride. The ESR spectrum of a mixture of PC (250 yg) and native soy protein (20 mg) homogenized in water by sonication resembled that observed for PC alone before sonication. However, when PC (250 yg) was sonicated in the presence of heat-denatured soy protein (20 mg), splitting of the ESR signal occurred. On this basis, they postulated the existence of two phases PC making up a fluid lamella phase and PC immobilized probably due to the hydrophobic interaction with the denatured protein. In a study of a soy-milk model, Ohtsuru et al. (25) reported that a ternary protein-oil-PC complex occurred when the three materials were subjected to sonication under the proper condition. Based on data from the ESR study, a schematic model has been proposed for the reversible formation-deformation of the ternary complex in soy milk (Figure 2). 

Figure 3. Phase diagram including the hockey puck and lamellae phases. The phases are (I) bilayer lamellae, (II) monolayer lamellae, (III) bilayer hockey pucks, (IV) mono-layer hockey pucks, and (V) incomplete monolayer lamellae. Log(v3x) is plotted against X. X = <-/>/( 1 — ) where is the volume fraction of the coil, v = k/X and k = Na -ZL2 where the coil part is assumed to consist of Nsegments with a mean-square separation between adjacent segments of 6a2, and L is the rod length. % is the Flory—Huggins interaction parameter.

Liquid crystallinity and block microphase separation both compete during the minimization of free energy of the system. As we will show later in this review, in the case of a rod-coil diblock copolymer, liquid crystallinity plays a very important role in the microphase separation process and leads to morphologies distinctly different from the conventional spheres, cylinders and lamellar microstructures and include the arrow head, zig-zag, and wavy lamellae phases [40, 41], In the case of SGLC-coil... 

G glassy state, Dl discotic lamella phase, Nd discotic nematic phase, Colhi hexagonal columnar phase, I isotropic phase... 

Eccleston [19] reviewed the emulsion stability factors on the basis of the HLB and of the DLVO theory. He emphasized the Friberg school results which show that the presence of liquid crystals stabilizes the emulsions by delaying the film-thinning process and, consequently, by reducing the rate of coalescence. He also mentioned stabilization by the formation of a gel network (surfactant-fatty alcohol-water system). Dahms [20] explained the role of fatty alcohol as a viscosity modifier on the basis of lamella-phase generation. 

Rharbi, Y. and Winnik, M.A. (2001) Interface thickness of a styrene-methyl methacrylate block copolymer in the lamella phase by direct norrradiative energy... 

At diblock concentrations above bicontinuous microemulsion ( tE) and of lamella ordered phases were identified [46]. While the lamella phase was predicted by mean field theory, the observation of a microemulsion phase was unexpected. Polymer microemulsion phases are presently the subject of active research both from theory [85] and experiment [52] and, in addition, seem to generate interest for industrial application because of its homogeneous structiue on the pm length scale. 

Composite Strengthening. An alternative strengthening method which holds great promise for producing advanced high temperature aUoys involves the incorporation of fibers or lamellae of a strong, often brittle phase, in a relatively weak, ductile, metallic matrix. This technique has been... 

Iron carbide (3 1), Fe C mol wt 179.56 carbon 6.69 wt % density 7.64 g/cm mp 1650°C is obtained from high carbon iron melts as a dark gray air-sensitive powder by anodic isolation with hydrochloric acid. In the microstmcture of steels, cementite appears in the form of etch-resistant grain borders, needles, or lamellae. Fe C powder cannot be sintered with binder metals to produce cemented carbides because Fe C reacts with the binder phase. The hard components in alloy steels, such as chromium steels, are double carbides of the formulas (Cr,Fe)23Cg, (Fe,Cr)2C3, or (Fe,Cr)3C2, that derive from the binary chromium carbides, and can also contain tungsten or molybdenum. These double carbides are related to Tj-carbides, ternary compounds of the general formula M M C where M = iron metal M = refractory transition metal. 

When one starts with a liquid of concentration Cg at a high temperature, and cools it down to a temperature slightly below Tg, a solid will grow which consists of two phases, which appear alternatively as lamellae or as fibers of one phase in a matrix of the other phase. 

Multiphase gold or palladium-based alloys never show dissolution of Au or Pd but often exhibit progressive surface ennoblement due to selective dissolution of copper or silver from the outer 2-3 atomic layers Heat treatment often decomposes multicomponent alloys into a Pd-Cu rich compound and an Ag-rich matrix with corrosion of the latter phase in deaerated artificial saliva and S -containing media . Au-Cu-rich lamellae have similarly been observed, again with preferential attack on Ag-rich phases or matrix. These effects presumably arise from the ability of the noble alloy phases to catalyse the cathodic reduction of oxygen . 

---