Cubic sphere phase spherical domains

UsingTEM to identify blend morphology, two diblocks with/ps 0.8 that form cubic-packed spherical phases and cylindrical phases respectively in the pure copolymer were found not to macrophase separate in a blend with d = 2.2, but to form single domain structures (cylinders or spheres) in the blend (Koizumi et al. 1994c). Similarly, blending a diblock with fK = 0.26 with one with fK = 0.64 (d = 1.2) led to uniform microphase-separated structures, with a lamellar phase induced in the 50 50 blend. Vilesov et al. (1994) also observed that blending two PS-PB diblocks with approximately inverse compositions (i.e. 22wt% PS and 72 wt% PS) induces a lamellar phase in the 50 50 blend. These examples all correspond to case (i). 

Asymmetric block copolymers which form hexagonal or cubic-packed spherical morphologies in the bulk, form stripe or circular domain patterns in two dimensions, as illustrated in Figure 5. The stripe pattern results from cylinders lying parallel to the substrate, and a circular domain surface pattern occurs when cylinders are oriented perpendicular to the substrate, or for spheres at the surface. Bicontinuous structures cannot exist in two dimensions therefore the gy-roid phase is suppressed in thin films. More complex multiple stripe and multiple circular domain structures can be formed at the surface of ABC triblocks (83). Nanostructures in block copolymer films can be oriented using electric fields (if the difference in dielectric permittivity is sufficient), which will be important in applications where parallel stripe (84) or perpendicular cylinder configurations (85) are desired. 

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