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New Epitaxial Phase Transition between DG and HEX in PS-<i>b</i>-PI
Park, Hae-Woong,Jung, Jueun,Chang, Taihyun,Matsunaga, Kazuyuki,Jinnai, Hiroshi American Chemical Society 2009 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.131 No.1
<P>We investigated the epitaxial phase transition from double gyroid (DG) to hexagonally packed cylinder (HEX) phases of a polystyrene-b-polyisoprene diblock copolymer in a thin film on a Si wafer substrate. The internal structure of the thin film was investigated by grazing incidence small-angle X-ray scattering, transmission electron microscopy, and transmission electron microtomography (TEMT). TEMT allows observation of the 3D-image of coexisting DG and HEX directly. Good domain orientation in the thin film and direct 3D-imaging of TEMT made it possible to observe the coexisting phase of DG and HEX, and a new epitaxial transition path from DG to HEX was found.</P>
Effect of Film Thickness on the Phase Behaviors of Diblock Copolymer Thin Film
Jung, Jueun,Park, Hae-Woong,Lee, Sekyung,Lee, Hyojoon,Chang, Taihyun,Matsunaga, Kazuyuki,Jinnai, Hiroshi American Chemical Society 2010 ACS NANO Vol.4 No.6
<P>A phase diagram was constructed for a polystyrene-<I>block</I>-polyisoprene (PS-<I>b</I>-PI, <I>M</I><SUB>W</SUB> = 32 700, <I>f</I><SUB>PI</SUB> = 0.670) in thin films on Si wafer as a function of film thickness over the range of 150−2410 nm (7−107<I>L</I><SUB>0</SUB> (<I>L</I><SUB>0</SUB>: domain spacing)). The PS-<I>b</I>-PI exhibits a variety of ordered phases from hexagonally perforated lamellar (HPL) <I>via</I> double gyroid (DG) to hexagonally packed cylinder (HEX) before going to the disordered (DIS) phase upon heating. The morphology of the PS-<I>b</I>-PI in thin film was investigated by grazing incidence small-angle X-ray scattering, transmission electron microscopy, and transmission electron microtomography. In thin film, the phase transition temperature is difficult to be determined unequivocally with <I>in situ</I> heating processes since the phase transition is slow and two phases coexist over a wide temperature range. Therefore, in an effort to find an “equilibrium” phase, we determined the long-term stable phase formed after cooling the film from the DIS phase to a target temperature and annealing for 24 h at the temperature. The temperature windows of stable ordered phases are strongly influenced by the film thickness. As the film thickness decreases, the temperature window of layer-like structures such as HPL and HEX becomes wider, whereas that of the DG stable region decreases. For the films thinner than 160 nm (8<I>L</I><SUB>0</SUB>), only the HPL phase was found. In the films exhibiting DG phase, a perforated layer structure at the free surface was found, which gradually converts to the internal DG structure. The relief of interfacial tension by preferential wetting appears to play an important role in controlling the morphology in very thin films.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-6/nn1003309/production/images/medium/nn-2010-003309_0003.gif'></P>