Core-shell-type microspheres

These core-shell type microspheres have very interesting structural features in that the cores are hardly crosslinked and the shell chains are fixed on the core surface with one end of the shell chains. The other end of the shell chains is free in good solvents for the shell chains. As the result of such a specific structure, the solubilities of the core-shell type polymer microspheres are governed by, not the core, but by the shell sequences, and the core-shell structures do not break even in the dilute solution [9,10]. 

As described in the Introduction, because of the structural similarity of the core-shell type microspheres to the (AB)n type star block copolymers with many arms... 

The morphology obtained from the blend of the core-shell type microspheres and AB type block copolymers with spherical morphology is shown next [37]. Figure 12 shows the typical morphologies of the blend ob-... 

Composite core-shell type microspheres were prepared by in situ heterogeneous polymerization on monodispersed seed latex particles suspended in an aqueous magnetite dispersion stabilized with sodium oleate (58). 

Figure 1 Schematic presentation of synthesis routes on core-shell type microspheres.

Figure 3 Transmission electron micrograph of core-shell type microsphere SVl-M. (From Ref. 28.)...

In a previous work [35], we studied the morphological behavior of core-shell type microspheres prepared from casting solution onto a carbon substrate. The particles of core-shell type microspheres were well aligned in a hexagonal array on the carbon substrate from two-dimensional observation. It was expected that in the core-shell type microspheres, such crystalline order in solu-... 

Table 3 Characteristics of Core-Shell Type Microspheres...

The core-shell type microspheres can be considered the smallest units in the microphase-separated structure. The properties of the microsphere in the solvent area are governed not only by the core but also by the shell chains in a good solvent for the shell. Thus, the core-shell type microspheres can be thought of as one spherical molecule with multibranches in the solvent. Thus, core-shell type microspheres can be used as composite materials in blends for the introduction of spherical microdomains into a matrix. The effect of the ordering of microspheres on the morphology of the blend has not been investigated. 

We investigated the morphologies of blends of well-ordered core-shell type microsphere with AB diblock copolymers, which form lamellar or spherical microdomains in a matrix [45,46]. The poly(S-Z>-4VP) with lamellar morphology or poly(S-Z>-4VP), poly(S-Z>-2VP), and poly(S- -I) with spherical morphology, synthesized by anionic polymerization, were chosen as the blend materials. The results are listed in Table 7. The P4VP core-PS shell microsphere SV500-M used in this work easily forms an ordered structure on its own. Some characteristics of the microsphere SV500-V are shown in Table 8. 

The interest in star polymers arises from their compactness and from their enhanced segment density. Essentially, both the core-shell type microspheres and... 

The (AB) and star copol)miers were obtained by organized polymerization of diblock macromonomers. The (AB) star copolymers (volume fraction of B blockf= —0.2) formed a lattice with a BCC structure near the C. In bulk film, this structure changed to an FCC lattice. Not only the core-shell type microspheres but also star copolymers led to hierarchical structure transformation of cubic lattice in the film formation to minimize the thermodynamic energy. 

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