Two-phase domain structure

Dynamic viscoelastic and stress-optical measurements are reported for blends of crosslinked random copolymers of butadiene and styrene prepared by anionic polymerization. Binary blends in which the components differ in composition by at least 20 percentage units give 2 resolvable loss maxima, indicative of a two-phase domain structure. Multiple transitions are also observed in multicomponent blends. AU blends display an elevation of the stress-optical coefficient relative to simple copolymers of equivalent over-all composition. This elevation is shown to be consistent with a multiphase structure in which the domains have different elastic moduli. The different moduli arise from increased reactivity of the peroxide crosslinking agent used toward components of higher butadiene content. 

So-called underpotential deposited species arise when an electrochemical reaction produces first, on a suitable substrate adsorbent metal, a two-dimensional array or in some cases two-dimensional domain structures (cf. Ref 100) at potentials lower than that for the thermodynamically reversible process of bulk crystal or gas formation of the same element. The latter often requires an overpotential for initial nucleation of the bulk phase. The thermodynamic condition for underpotential deposition is that the Gibbs energy for two-dimensional adatom chemisorption on an appropriate substrate must be more negative than that for the corresponding three-dimensional bulk-phase formation. Underpotential electrochemisorption processes commonly involve deposition of adatoms of metals, adatoms of H, and adspecies of OH and O. 

In the two phase domains (S < Sx and S > S2), we were able to dilute the microemulsion phases. This led us to picture the microemulsions phases as a dispersion of droplets of oil (resp. water) in water (resp. oil). These droplets are surrounded by a layer of surfactant and co-surfactant. This dilution procedure allows us to define the composition of the continuous phase (1) (2). No dilution procedure was found in the three phase domain Sx< S < S2, thus supporting the idea that the structure of the middle-phase mieroemulsion is more complicated than a mere dispersion of droplets. 

At this point, we had the first four of the seven characteristic features of A-B-A thermoplastic elastomers, as shown in the box. That is, we were completely confident that we had a three-block polymer, rubbery behavior with high tensile strength in the unvulcanized state, and also complete solubility. We concluded from these properties that these polymers were two-phase systems. We then generated the essentials of the two-phase, domain theory and visualized the physical structure illustrated schematically in Figure 1. We also visualized applications in footwear, in injection-molded items, and in solution-based adhesives. Positive confirmation of the two-phase structure quickly followed, by detection of two separate glass transition temperatures, as well as observation of the thermoplasticlike reversibility of bulk- and... 

As discussed above, lipid membranes are dynamic structures with heterogeneous structure involving different lipid domains. The coexistence of different kinds of domains implies that boundaries must exist. The appearance of leaky interfacial regions, or defects, has been suggested to play a role in abrupt changes in solute permeabilities in the two-phase coexistence regions [91,92]. 

Figure 10.2 Adsorbed sulfur structures on Cu(lll). (a) Model of the (x/7 x x/7) R19° phase showing the Cu4S tetramers large grey circles are added coppers, smaller circles represent S. (b) Filtered 50 x 50 nm STM image of coexisting ( /l x y 7) R19° and complex structures, (c) 5 x 5nm STM image of domain boundary between the two phases. (Reproduced from Refs. 6 and 7).

Equations. For a ID two-phase structure Porod s law is easily deduced. Then the corresponding relations for 2D- and 3D-structures follow from the result. The ID structure is of practical relevance in the study of fibers [16,139], because it reflects size and correlation of domains in fiber direction . Therefore this basic relation is presented here. Let er be50 the direction of interest (e.g., the fiber direction), then the linear series expansion of the slice r7(r)]er of the corresponding correlation function is considered. After double derivation the ID Fourier transform converts the slice into a projection / Cr of the scattering intensity and Porod s law... 

D Structural Entities. In materials science, stmctural entities which can satisfactorily be represented by layer stacks are ubiquitous. In the field of polymers they have been known for a long time [156], Similar is the microfibrillar [157] structure. Compared to the microfibrils, the layer stacks are distinguished by the large lateral extension of their constituting domains. Both entities share the property that their two-phase structure is predominantly described by a ID density function, Ap (r3), which is varying along the principal axis, r3, of the structural entity. 

Figure 8.24. Demonstration of the edge-enhancement principle built into the chord length distribution, (a) Two-phase structure intersected by a straight line, (b) The density along the line, (c) The derivative of the density is a sequence of 5-functions which are marking the positions of the domain edges...

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