Photoinduced disorder in strongly segregated block copolymer composite films for hierarchical pattern formation.

Submicrometer patterns of adjacent, well-ordered and disordered domains were obtained using optical lithography by area-selective, photoinduced disordering transitions within block copolymer composite films. Enantiopure tartaric acid was blended with poly(ethylene oxide-block-tert-butyl acrylate), PEO-b-PtBA, copolymers to yield well-ordered films. In the presence of triphenylsulfonium triflate, a photoacid generator, photoinduced disorder was achieved upon UV-exposure by deprotection of the PtBA block to yield poly(acrylic acid). Poly(acrylic acid) is compatible with both PEO and tartaric acid and deprotection yields a phase mixed material and disorder within seconds. Tartaric acid performs two additional functions in this system. First, it increases segregation strength in PEO-b-PtBA, enabling well-ordered systems at low BCP molecular weights, small domain sizes, and rapid disordering kinetics. Second, the presence of tartaric acid suppresses PEO crystallization, resulting in smooth films and eliminating the influence of PEO crystallization on film morphology.