Accelerated lattice transition of sphere-forming block copolymer in thin films under solvent vapor
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초록
내용
Block copolymers (BCPs) are versatile materials that can be used as self-assembled or as templates to fabricate metallic or inorganic nanostructures. When fabricating BCPs, solvent vigorously influences the final morphologies by the degree of solvent uptake, solubility parameters for each block, and so on. In this study, we discover the accelerated lattice transition of sphere-forming BCPs under solvent vapor. Under solvent vapor, spheres dynamically split into several layers according to the swelling ratio (SR), changing their stable hexagonal lattice structure at lower SR to a face-centered orthorhombic (FCO) lattice at higher SR. Our in-situ and ex-situ analysis found that BCPs respond to the swelling ratio to maintain their equilibrium chain length, described with L0. Furthermore, their transition pathway resembles thickness-dependent lattice transition behavior, which means lattice structure is only determined by the number of layers.