Block copolymers have received great attention due to its unique self-assembled domains of lamellae, cylinders and spheres. Over the last few decades, block copolymer thin films have been studied as alternative non-lithographic tools for nano-scale patterning, which can be applicable to nano-electronics, biological assay, or high-density storage. Key to the use of block copolymers for such applications is controlling the orientation and lateral order of the microdomains in thin films. For instance, the preference of substrate surface to block copolymer and the gap between two substrates are dominant factors determining the orientation of lamellar structures. Moreover, for enhancing or controlling the lateral order of the microdomains in block copolymers, patterned substrates have been used as confined geometries. Recently, as two-dimensional confined geometries, the cylindrical pores in anodic alumina template were used for microphase separation of block copolymers. Theoretical studies were also conducted for the cylindrically confined system, and predicted various unusual morphologies such as single helices, double helices and hoops. Recently, three-dimensional confined geometry has been also studied by a few research groups. For instance, onion-like structures were produced by capillary infiltration of diblock copolymers into the inverted opals. Okubo and his colleagues reported microspheres with cylindrical, spherical and lamellar morphologies by simple evaporation-induced microphase separation inside droplets. Theoretically, such onion-like internal structures have been investigated by Monte Carlo simulation. However, the ratio of the sphere diameter (D) to the lamellar spacing (L0) was nearly one hundred in those experiments, which means that the curvature of the confined geometry was too small to affect the directional orientation of microdomains. For an appreciable confinement effect, the ratio (D/L0) should be lowered to order of 1 as in the theoretical investigation on cylindrical confinement, in which anomalous microphases were observed for 0.5展开▼
