Phase Behavior in Thin Films of A2B and A4B type Miktoarm Star Copolymers
- Phase Behavior in Thin Films of A2B and A4B type Miktoarm Star Copolymers
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- Block copolymer materials are used in many areas and play important roles in industry. To study the property and mechanism of block copolymer is very valuable. In this research, thin films of miktoarm star copolymer were investigated depending on type of miktoarm and film thickness. In Chapters 3 and 4 of this thesis, A2B and A4B type miktoarm star copolymer composed two poly(styrene) and polylactide are studied in thin films.
Chapter 1 details the fundamentals and examples of block copolymer, such as composition, physical factors of phase behavior. And block copolymer thin film is intoroduced. Also, other types of block copolymers are introduced like miktoarm or blanch or Y shape molecules.
In Chapter 2, Synthesis of miktoarm star copolymers, preparation of thin film and grazing incidence small angle X-ray scattering (GISAXS) technique used in this research are introduced.
In Chapter 3, the A2B miktoarm star copolymer composed poly(styrene) and polylactide are investigated in thin film. As determined by a small angle X-ray scattering (SAXS) technique, the prepared (PS)2-b-PLA miktoarm star copolymer showed a 2-D hexagonal cylinder structure in the bulk state. In thin film, (PS)2-b-PLA showed the different phase behavior depending on the thickness. The thickness of thin film affected their phase behavior. The chain end effect is introduced the reason of phase in thin film.
Another molecules, (PS)4-b-PLA, is introduced in Chapter 4. We envisioned that the degree of branching would be an important structural parameter to affect the thin film morphology. To this end, (PS)4-b-PLA consisting of a tetra-branched PS and linear PLA is investigated. As compared to previous (PS)2-b-PLA, the PS and PLA blocks have almost identical molecular weight, but the PS block is tetra-branched. Therefore, it can be considered that a thin film morphological difference between the two examples may be attributed to the degree of branching in the PS block.
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