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

9C, 10C/2003G229

Features of microphase - separated structures in S1BS2 triblock copolymers
having different lengths of end - block chains
Eiji Funai1), Kimiyuki Shirouchi1), Yoshihiro Tsuji1), Yusuke Sugino2), Shigeo Hara2), Katsuhiro
Yamamoto2), and Shinichi Sakurai1)
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, JapanExperimental
The SBS samples have Mn of about 4.7 × 104 forGroup 1 (six samples) and about 7.1 × 104 for Group 2(five samples). The values of Mw/Mn are about 1.05 andφPS of about 0.67 for all samples.
The solution cast of the SBS triblock copolymer using
a neutral solvent (toluene) was conducted to prepare
equilibrium microdomain structure. The as-cast samples
were then thermally annealed at 170˚C for 2 hours. The
SAXS measurements were conducted to reveal
microdomain morphology in the annealed samples.

References[1] M. W. Matsen, J. Chem. Phys. 113, 13 (2000)* shin@kit.jp
1011
1.158log [ I(q) / a. u. ]Introduction
We report experimental results on relationship between
primary (chemical) structures and morphology of
microdomains of block copolymers. For this purpose, we
prepared various asymmetric styrene-butadiene-styrene(SBS) triblock copolymers having different lengths of end
blocks. The morphology was examined by small-angle
X-ray scattering (SAXS) and transmission electron
microscopy (TEM).

¦46158Users' Reportτ = 0.50 G
τ = 0.47 C141.152110

τ = 0.40 G

22-2-4
00.2

0.4

0.6

0.8

1.0q / nm-1

τ = 0.27 PL
τ = 0.32 PL

101182log [ I(q) / a. u. ]Results and Discussion
Although total molecular weight, composition, andtemperature were kept constant, the morphology was
found to change with a degree of difference in length ofend blocks. One typical example exhibits a morphologicalchange as cylinder -> lamella -> cylinder with a decreaseof length of one polystyrene (PS) end block, while
keeping the total PS composition constant. This curious
morphological behavior exhibiting a re-entrant typechange is qualitatively in good accord with the theoreticalresult presented by Matsen [1]. Fig. 1 shows changes inSAXS profiles with τ where ones in red are for Group
1samples and ones in blue are for Group 2 samples. Here,the parameter τ denotes the degree of asymmetry, asdefined by MS / (ML + MS), where MS and ML stand forshorter and longer PS end-block chains, respectively.
Namely, τ = 0.5 for a symmetric triblock copolymer SBS,and τ = 0 for a diblock copolymer SB. Abbreviations L,G, C, and PL designate lamella, gyroid, cylinder andperforated lamella, respectively.

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4
1 14

τ = 0.25 L
τ = 0.24 L

2224

4
1 10

τ = 0.13 L
τ = 0.11 L

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-4
0

0.2

0.4

0.6
-1

0.8

1.0

τ=0C
τ=0Cq / nm
Fig. 1 Changes in SAXS profiles with τ where ones in
red are for larger molecular weight samples and onesin blue are for shorter molecular weight samples with asimilar degree of asymmetry, τ. Abbreviations L, G,C, and PL designate lamella, gyroid, cylinder andperforated lamella, respectively.