Domain boundary thickness

In contrast to measurements of the interfacial tension coefficient, only few measurements of the interphase thickness have been reported [Wlochowicz and Janicki, 1989 Janicki et al, 1986]. For example, domain boundary thickness were measured in PS/PMMA blends [Foster et al, 1990 Fernandez et al, 1988 Russel et al, 1991 Perrin and Prud homme, 1994]. Generally, values in the range of 2-6 nm were reported for the interface thickness. 

PS/PMMA P(S-b-MMA) Neutron reflectivity using blends with high copolymer content and an equal amount of homopolymers. The micro-domain boundary thickness was found to increase by 25% from the pure copolymer to a mixture containing 17% homopolymer A1 = 2 nm. Russel et al., 1991b... 

Cakmak M. and Wang M.D., Structure development in the tubular blown film of PP/EPDM thermoplastic elastomer, Antec 89, 47th Annual Tech. Conference of SPE, New York, May 1, 1989, 1756. Hashimoto T., Todo A., Itoi H., and Kawai H. Domain boundary structure of styrene-isoprene block copolymer films cast from solution. 2. Quantitative estimation of the interfacial thickness of lamellar microphase systems. Macromolecules, 10, 377, 1977. 

C.2.1. PdlAl20s Preparation and Structural Properties. To prepare a thin well-ordered AI2O3 model support, a NiAl(l 10) alloy single crystal was oxidized in 10 mbar of O2 at 523 K (290). The structure of the alumina film was examined by a variety of techniques (see Reference (101) and references cited therein), and recently it was even possible to image its atomic structure by STM at 4K (Fig. 19) (215). The alumina film was only approximately 0.5 nm thick and hydroxyl-free, and one should also keep in mind that its exact structure may deviate from those of bulk aluminas (101,215,292,293). Its properties are certainly influenced by the observed line defects (antiphase domain boundaries and reflection domain boundaries). 

Most of the surface was found covered by a thick coke film (ca. 2 nm to 6 tun) in the form of individual clusters, which fiised into a "flower" type pattern (agglomerates). Note the clear domain boundaries around each carbon "flower pattern. Regarding the shape of the observed carbon features it could be concluded that during formation, carbon coke clusters possess some kind of limited mobility. These coke deposits possibly grow by spreading over the catalysts surface via a branching mechanism. Fig. 4e shows an AFM image recorded at the... 

Ajji and Utracki [1996, 1997] and in Chapter 2 Thermodynamics of Polymer Blends in this handbook. The interface thickness of A/A-B mixtures was not theoretically calculated, but experimental measurements indicate that the presence of the homopolymer leaves the domain boundary unchanged [Bates et al., 1983 Hashimoto et al., 1990 Tanaka et al., 1991 Zin and Roe, 1984 Green et al., 1989]. On the other hand, the part of the phase diagram where the concentration of the block copolymer in the mixture is low, was studied in detail [Whitmore and Noolandi, 1985b Leibler et al., 1983 Leibler, 1988]. The proposed models were similar. In both, the conditions for the formation of spherical micelles were investigated and expressions of the critical micelle concentration, were derived. For example... 

The normal state of a ferroelectric crystal is one in which the microstructure consists of a set of coherent domains, each of which has the internal electric dipoles parallel to each other, but not aligned with those of neighbouring domains. Domain walls are not atomically smooth but have a thickness of between 0.5 and 1 nm. Polarisation builds up at domain boundaries and a single domain can have surface charges of the order of 1.5 x lO electrons cm which can generate an internal electric field of 300MV or more. 

It should be remembered that it was necessary, in order to derive (9), to assume that the Boltzmann equation (1), (la) holds throughout the whole space. If this is not the case (9) will not hold even in that part of the sphere where (1), (1 a) does. In particular, if the whole space contains two different media, (9) will not hold in either medium in the neighborhood of their boundary. It is clear, however, that the deviations will be restricted in both media to a domain the thickness of which is of the order of the mean free path 1/a. 

In summary, Helfands NIA theory predicts molecular weight dependencies of domain size, separation and other parameters of the phase separated copolymers with the presumption of an interface of constant thickness at the-domain boundary. 

Solution-grown single lamellar crystals of, eg, PEO (147), POM (148), PE (149,150), syndiotactic PP, poly(dimethyl silane) (151), poly(4-methyl-pentene) (152), and poly[(i )-3-hydroxybutyrate] (153) deposited onto solid substrates have been studied by SFM. The habit and thickness of the lamellae in flat-on projection are directly accessible and in addition to these data, which have previously been typically provided by TEM in conjunction with shadow evaporation techniques (4), more subtle details of domain boundaries and fold direction orientation have been revealed. In Figure 14, the habit of a collapsed PE lamellae is depicted, as well as the anisotropic lateral force recorded in the different fold sectors (154). 

Block copolymers composed of incompatible components of A and B form in general a "pseudo two-phase" structure in solid state as a consequence of microphase separation in solidification process. There exists interfacial domain boundary region of a certain thickness where the incompatible components are mixed in between the regions composed of pure A and B segments. Origin of such interphase has recently been studied intensively on the basis of statistical thermodynamics by Meier(l), Helfand(2), and others. Number of works on the mechanical properties of block and graft copolymers have also proposed the existence of the interphase(3-9). 

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