Development of Sub-5 nm Patterning by Directed Self-Assembly using Multiblock Copolymers

Polystyrene-b-poly(4-hydroxystyrene) (SH) with narrow molecular weight distribution (M-w/M-n<1.1) has been successfully synthesized by living anionic polymerization technique. It was confirmed that the SH diblock copolymer with molecular weight of 27k and with volume fraction of S of 0.68 showed the definite alternative lamellar structure with domain spacing of 20.8 nm (the half pitch (HP) of 10.4 nm). Furthermore, monodisperse SHSH tetrablock copolymers with molecular weight of 27k and 23k have been also synthesized, and from these copolymers formations of lamellar structure with the HP of 5.4nm and 4.9nm, respectively, were observed by TEM and SAXS measurements. Moreover, not only the synthesis of the block copolymers by anionic polymerization in experimental lab scale up to 25 g, but a preparation of well-defined block copolymers by large-scale anionic polymerization over 3 kg was also developed.