Block copolymer permeable membrane with visualized high-density straight channels of poly(ethylene oxide)

A simple fabrication, scalable to centimeter scale, of a permeable membrane made of block copolymer containing molecular transport channels is demonstrated by coating photo-crosslinkable liquid-crystalline block copolymer, consisting of poly(ethylene oxide) (PEO) and poly(methacrylate) (PMA) bearing stilbene (Stb) mesogens in the side chains (PEO₁₁₄-b-PMA(Stb)₅₂), onto a sacrificial cellulose acetate film substrate. After thermal annealing, perpendicularly aligned and hexagonally arranged PEO cylindrical domains with a surface density of 10¹¹ cm^-2 were formed and then fixed efficiently by photo-crosslinking the stilbene moieties in the PMA(Stb) domains by [2 + 2] dimerization. The fully penetrating straight PEO cylindrical domains across the 480-nm-thick membrane were well-defined and visualized as molecule-transport channels. After exfoliated by removal of the cellulose acetate layer, the membrane could be transferred onto another substrate by either scooping or a horizontal lifting method. Throughout the processes, the fully penetrating PEO channels across the membrane are preserved to open at both ends. A simple permeation experiment demonstrates that rhodamine dyes permeate efficiently through the PEO cylindrical channels of the annealed membrane but not across a non-annealed one.