Anisotropic Optical Properties and Structures of Block Copolymer/Silica Thin Films Containing Aligned Porphyrin J-Aggregates

Mesostructured silica−block copolymer thin films are demonstrated to provide orientationally ordered host matrixes for stable alignment of coassembled porphyrin J -aggregates with anisotropic optical properties. Visible light at 490 nm was absorbed anisotropically ( A ∥ / A ⊥ = 1.35) by aligned, hexagonally ordered (ethylene oxide) 20 −(propylene oxide) 70 −(ethylene oxide) 20 (P123) triblock copolymer/silica nanocomposite films containing 1−5 wt % tetrakis(4-sulfonatophenyl)porphyrin (TPPS 4 ) guest species in the form of J -aggregates. Amorphous silica prepared similarly and containing TPPS 4 J -aggregates, but without structure-directing block copolymer species, absorbed light isotropically ( A ∥ / A ⊥ = 1.00). The porphyrin guest species were determined to be preferentially associated with the hydrophilic ethylene oxide moieties of the triblock copolymer, by using two-dimensional (2D) solid-state 1 H{ 1 H} and 13 C{ 1 H} NMR correlation experiments, including under conditions of fast (45 kHz) magic-angle spinning. Interrelationships are shown and established among synthesis conditions, the molecular, mesoscopic, and orientational structural ordering in the porphyrin-containing nanocomposite thin films, and their macroscopic optical properties.