| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 92 === Microphase separation in self-assembled diblock copolymers may generate a series of long-range ordered microdomain morphology (1-D stacked lamellae, hexagonally packed cylinders, gyroid, and BCC packed spheres) depending on the strength of interblock repulsion and the composition of the constituting blocks. In the present research, we have investigated the morphologies of self-assembled blend system constituting of a diblock copolymer polystyrene-b-polyisoprene (PS-b-PI) and a homopolymer polystyrene (PS) exhibiting lamellae and bicontunious gyroid periodic microstructures as 1-D and 3-D photonic crystals materials. Through blending PS and PI homopolymer with a lamellae-forming PS-b-PI with short block length, we have systematically increased the lamella thickness, while effectively retaining the long-range order. The resultant blends exhibits excellent visible light (350~600 nm) reflectance with wavelength tunable by the lamellar thickness. Further a bicontinuous gyroid morphology has been successfully generated in PS-b-PI/PS blend. The PI phase in these blends were selectively degraded using ozone to yield thin films containing bicontinuous nano-channels. The nanoporous film thus produced is expected to display high refractive index contrast useful for 3-D photonic crystal applications. In addition, the hierarchical structures of polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) and dodecylbenzene sulfonic acid (DBSA) complex systems were investigated by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The ionic ally bonded diblock copolymer-surfactant complex was observed to form supramolecules exhabiting structure-within-structure morphology at two length scales. A new morphology of square-packed cylinder-within-lamellae has been observed in the PS-b-P4VP(DBSA)0.5/0.75 system which could be ascribe to the homogeneous binding between P4VP chain and DBSA. The more stretched P4VP chains can reach to fill the corner of the Wigner-Seitz cell of square lattice to relieve the higher packing frustration so that the stability of square-packed cylinder-within-lamellae is enhanced. This interesting morphology is quit different from the usually observed hexagonally packed cylinder morphology and could be useful for 2-D pattern nanomaterial applications.
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