Formation of the Wrinkle Structure on a Styrene-Butadiene-Styrene Block Copolymer Surface by Surface Chemical Reformation via Ion-Beam Irradiation

A styrene-butadiene-styrene (SBS) block copolymer was utilized to fabricate the wrinkle pattern in accordance with the buckling theory via ion-beam (IB) irradiation that induced surface reformation resulting in modulus mismatch and compressive strain. Using several analyses, different wrinkle patterns on the SBS surface were observed as the IB incidence angle was increased. After IB irradiation, a random labyrinth pattern was achieved at all IB incidence angles except for 15 degrees, with which a less-formed wrinkle pattern was observed. Chemical analysis revealed that IB irradiation induced reformation of the surface chemical composition resulting in a stiff surface skin layer on the wrinkle pattern. The morphology of the wrinkle pattern was numerically and visually investigated, the results of which indicate that large wavelength and amplitude were achieved at high IB incidence angles. Through the buckling theory and the results of the surface analyses, the reason for this phenomenon was established: the IB incidence angle was the most important factor for determining the size of the wrinkle pattern on the SBS substrate. Consequently, it was verified that the wavelength and amplitude of the wrinkle pattern can be controlled by varying the IB incidence angle to the SBS substrate.