Photon Factory Activity Report 2005 #23 Part B (2006)
Materials Science

9C, 10C/2005G186

Control of surface ordering of spherical microdomains of block copolymers byutilizing the order-disorder transition in bulk
Shinichi Sakurai*, Hidekazu Yoshida, Yoshihiro Tsuji
Department of Polymer Science & Engineering,
Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, JAPANSurface ordering of spherical microdomains were
thoroughly examined by atomic force microscopic (AFM)
observations using polystyrene-b-polyethylenebutyleneb-polystyrene (SEBS) triblock copolymers with glassy
polystyrene (PS) spheres embedded in the rubbery
polyethylenebutylene (PEB) matrix. It was found that PS
spheres regularly order to form a hexagonal array on thefree surface when they regularly order in bulk, andviceversa. We quantitatively confirmed that the sphereordering in bulk affects regularity of sphere ordering on
the free surface.
The SEBS sample has a number-avergae molecular4
weight (Mn) of 6.7 × 10 , volume fraction of PS blocks(φPS) of 0.084 and polydispersity index (Mw / Mn) of 1.04.
The PEB mid-blocks were obtained by conductinghydrogenation of polybutadiene midblocks in a
precursory
polystyrene-b-polybutadiene-b-polystyrene(SBS) triblock copolymers. The content of a butylene
moiety in the PEB block is 50 mol%. The film sample
was obtained by evaporating the solvent (toluene) from a
5 wt% polymer solution at room temperature. After thesolvent was completely removed, an as-cast film obtained
was further annealed for 10 hours at 140˚C and 150˚C
that are above the glass transition temperature (Tg) of thePS blocks, followed by quenching into ice water.
Fig. 1 displays small-angle X-ray scattering (SAXS)
profiles for SEBS samples cast from 5-wt% polymer
solutions in toluene; (a) as-cast sample, (b) sample
annealed at 140˚C for 10 hours, and (c) sample annealed
at 150˚C for 10 hours. The profile (b) exhibits multiple
diffraction peaks from the bcc lattice, as indicated by
1/2
1/2
arrows with 1, 2 , 3 , while profile (a) or (c) shows asingle main peak with a shoulder, which is a signature ofdisordered arrangement of spherical microdomains. TheSEBS sample has been found to undergo the order-todisorder transition (ODT) at 150˚C. In the present work,
we have utilized these characteristic samples with andwithout regularity of spherical arrangement in bulk toexamine effects of bulk structure on surface ordering ofspherical microdomains.
The results of the AFM observation to examine thesurface morphology and the surface ordering arepresented together in Fig. 1. The brighter region specifies
a higher altitude and the extent of height is expressed by142

Users' Report

Fig.1 1d-SAXS profiles for SEBS samples cast from 5wt% polymer solutions in toluene; (a) as-cast sample,(b) sample annealed at 140˚C for 10 hours, and (c)sample annealed at 150˚C for 10 hours.
Fig.1 1d-SAXS profiles and corresponding AFM
height images on the free surface of SEBS samples
cast from 5-wt% polymer solutions in toluene; (a) ascast sample, (b) sample annealed at 140˚C for 10hours, and (c) sample annealed at 150˚C for 10 hours.
the brightness. Thus, it was found that round-shaped
domains consist of PS blocks and they are protrudent at
the free surface of the sample film. Panels (a), (b) and (c)are images of the free surface for an as-cast sample, asample annealed at 140˚C for 10 hours, and a sample
annealed at 150˚C for 10 hours, respectively. Note herethat those films were all obtained by casting 5-wt%
polymer solutions in toluene, and then the thermal
annealing was conducted with the condition specified.
The thickness of the films is in the range of 0.3~0.5 mm.
It is clearly seen that regularly arranged spheres wereonly observed in panel (b), whereas disorder of thepacking of spheres was found in panel (a) or (c). These
results are well correlated to the SAXS results, indicatingthat spheres also regularly order on the free surface when
the spheres regularly order in bulk, and viceversa.
* shin@kit.jp