Photon Factory Activity Report 2004 #22 Part B (2005)
Materials Science

9C, 15A/2003G228

Effects of pressure on spontaneous orientation of hexagonally packed cylindricalmicrodomains in polystyrene-b-polybutadiene-b-polystyrene triblock copolymers
Megumi Akemura1), Hidekazu Yoshida1), Yusuke Sugino2), Shigeo Hara2), Katsuhiro Yamamoto2), and1)
Shinichi Sakurai
1)
Department of Polymer Science & Engineering,
Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan2)
Department of Material Science & Engineering,
Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555, Japan
hwhm/hwhm0 can be a measure of cylinder orientation,although it is inversely proportional.
Then, the following facts can be concluded fromthe results shown in Fig. 2. At 0.1MPa, or relatively
low pressure, the cylinder orientation was remained
constant below a certain temperature (around 100°C
for the case of 0.1MPa), and then it was improved
exponentially above this temperature. Suddenly around
160°C, this trend was turned over such that thecylinder orientation started to become worse abruptly
for the subsequent increase of temperature. On thecontrary, for 200MPa or relatively high pressure, thecylinder orientation was linearly improved withtemperature. Interestingly, it was found that the trend
was also turned over around 160°C. Close examination
reveals that the temperature of the turning point has
little dependence of pressure. However, there seems to
be discernible pressure dependence on the minimum
value of hwhm/hwhm0 at the turning point, such thatthe most improved cylinder orientation can be obtained
at high pressure, 200MPa (around 160°C).
* shin@kit.jp

1.2µ(a)q = 0.3nm -1µhwhm / hwhm0

Block copolymers consisting of two or morechemically different monomer units connected at theirchain ends form various types of microphase-separated
structures, and their morphologies depend oncomposition and molecular weight of block
copolymers. Numerous studies on the control of the
microphase-separated structure have been reported, but
so far the effect of pressure on microphase-separated
structure has not been studied. So in this study we haveinvestigated the effect of the pressure on cylindricalmicrodomains in polystyrene(PS)-b-polybutadiene(PB)-b-polystyrene(PS) triblock copolymers using thesmall-angle X-ray scattering (SAXS). The characteri4
zation of the sample is as follows: Mn = 6.07×10 , wPS(weight fraction of PS) = 0.183, the PB midblocks
were partially hydrogenated, by which polyethylenebutylene type chemical structure is resulted, and thefraction of 0.51 of the PB blocks was hydrogenated.
The sample was subjected to one-dimensional
flow with a load of 1065g at 150°C for 20 seconds toalign cylinders packed in a hexagonal lattice. After theload was completely removed, SAXS measurements
were conducted under 0.1, 50, 100, 150, and 200MPa
with increasing temperature from 40 to 180°C. The
two-dimensional (2d-) SAXS measurements wereperformed at BL45XU SAXS beamline of SPring-8.
Fig.1 shows the 2d-SAXS pattern obtained under0.1MPa at 40°C and that obtained under 0.1MPa at
180°C, indicating that orientation of the cylinders was
spontaneously improved without application of theflow. We evaluated sharpness of the hexagonal spots todiscuss the degree of orientation. In fact, an averagepeak width (hwhm; half width at half maximum) of thesix spots was evaluated when the scattering intensity
was plotted as a function of the azimuthal angle. Fig. 2shows changes in thus obtained value of hwhm whenincreasing temperature from 40 to 180°C at a given
pressure. For clear comparison of the changes atvarious pressures, the value of hwhm was normalized
by its initial value at 40°C (hwhm0). Therefore,

1.0

0.80.1MPa
50MPa
100MPa150MPa200MPa0.60.4306090120150180Temperature(°C)(b)q = 0.3nm -1

Fig.1 2d-SAXSpatterns obtained
under 0.1MPa at
40°C(a) and at
180°C (b).

Fig.2
Changeinthenormalized peak width of thefirst-orderhexagonal
diffraction spots as afunction of temperature forvarious values of pressure,
0.1 – 200 MPa.

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