Photon Factory Activity Report 2017 #35 (2018)

BL-10C/2017G527

Orienting Cylindrical Microdomains in an SEBS Triblock Copolymer / Diluent Sheetby Application of Temperature Gradient
Ryo YAMANAKA1, Nobutaka SHIMIZU2, Noriyuki IGARASHI2,Hideaki TAKAGI2, Shinichi SAKURAI1,*
1

Department of Biobased Materials Science, Graduate School of Science and Technology, Kyoto
Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan2
Photon Factory, Institute of Materials Structure Science, High Energy Accelerator ResearchOrganization, Oho 1-1, Tsukuba, Ibaraki 305-0801, Japan

1 Introduction
Control of orientation of nanostructures in polymericmaterials has been attracting interests from academic andtechnological viewpoints because of demands ofproducing functional materials having anisotropic
properties. Applying temperature gradient is one of themost promising tactics for controlling orientation inpolymer systems. Perpendicular orientation was achievedfor cylindrical microdomains in block copolymer thinfilms by the application of temperature gradient. It wasalso reported that the crystalline lamellae were formed
parallel to the applied temperature gradient for acrystalline polymer. These examples of the experimental
studies clearly indicate the significance and thesuperiority of the application of the temperature gradient.
2 Experiment
The sample used in this study is an polystyrene-blockpoly(ethylene-co-butylene)-block-polystyrene(SEBS)
4
triblock copolymer with Mn = 6.60 ×10 and Mw/Mn = 1.03
(Mn: number-average molecular weight, Mw: weightaverage molecular weight). The total volume fraction ofPS (polystyrene) end-blocks is 0.16. Dioctylphthalate(DOP) was used as the diluent. Note that DOP has
selectivity in solubility for the SEBS; good solubility forPS while poor solubility for PEB. The composition ofSEBS/DOP was 6/4.
To impose temperature gradient to a specimen, wefabricated a set up such that the specimen was filled in the3-mm gap space (36 mm × 3 mm) in an aluminum platewith thickness of 1 mm. After the specimen was filled,
the top and bottom of the specimen were covered with thepolyimide film (25 µm thickness; Du Pont-TORAY Co,Ltd., Japan) and cover slip (0.12 - 0.17 mm thickness;
Matsunami Glass Ind., Ltd., Japan), respectively. The
reason of using the polyimide film is to minimize theabsorption of X-ray due to such window materials when
conducting measurements of the two-dimensional smallangle X-ray scattering (2d-SAXS) for the nanostructures
analyses, noting that the polyimide film is thinner thanthe cover slip so that the absorption is lesser. The sample
cell filled with the specimen was then fabricated so as toimpose the temperature gradient, where the right and left
sides of the sample cell were sandwiched by the metal
blocks of which temperatures were relatively lower andhigher, respectively. The high temperature block wasmaintained by the electric heater, while the cold

temperature by the water circulation supplied from areservoir.
Thermosensors(theadhesive-type
thermocouple(Chromel-Alumel),
ST-50,RKC
Instrument, Inc., Tokyo, Japan) were attached on thesurface of the sample cell at positions very close to thespecimen space to check their temperatures of both hotand cold sides.
The 2d-SAXS measurements were carried out at room
for the specimen after the application of the temperature
gradient to analyze nanostructures and their orientation.
The sample cell (the alminum plate) was picked up fromthe set-up and was subjected to the 2d-SAXS
measurements without removing the cover slip and thepolyimide film. The 2d-SAXS measurements wereconducted at the BL–10C beamline of the Photon Factory,
High Energy Accelerator Research Organization,
Tsukuba, Japan, using X-ray with a wavelength of 0.1488
nm. The sample-to-detector distance was 2.0 m. A
PILATUS-2M (DECTRIS Ltd., Baden, Switzerland) wasused as a two-dimensional detector.
3 Results and Discussion

Fig. 1 shows a schematic illustration of the revealedorientation of cylinders in the specimen thermallyannealed under the temperature gradient with 86 °C /143 °C for 3 h. Closer to the cold temperature side, theoverall orientation
is random, while
the cylinders areperpendicularlyoriented near thehigh temperatureside. Furthermore,
the result of thealmost
perfect
hexagonal spots inthe2d-SAXS
Fig. 1 Schematic illustration
pattern indicatesof the revealed orientation ofan orientation acylinders in the specimen
single grain state.
thermally annealed under thetemperature gradient with* shin@kit.ac.jp
86 °C / 143 °C for 3 h.