Highly Ordered Nanoporous Thin Films from Photocleavable Block Copolymers

Poly(styrene-block-ethylene oxide) with an o-nitrobenzyl ester photocleavable junction (PS-hv-PEO) was synthesized by a combined RAFT polymerization and click chemistry approach and represents the first report utilizing this method for the synthesis of photocleavable block copolymers. After solvent annealing, highly ordered thin films were prepared from PS-hv-PEO. Following a very mild UV exposure and successive washing with water, PS-hv-PEO thin films were transformed into highly ordered nanoporous thin PS films with pore diameters of 15-20 nm and long range ordering (over 2 mu m x 2 mu m). Afterwards the pores were filled with PDMS by spin-coating in combination with capillary forces. After treatment with oxygen plasma to remove the PS templates, highly ordered arrays of silica nanodots were obtained. This represents the first template application example from highly ordered nanoporous thin films derived from block copolymers featuring a photocleavable junction.