Web Release Date: January 30,
Anisotropic Optical Properties and Structures of Block Copolymer/Silica Thin Films Containing Aligned Porphyrin J-Aggregates
and
Department of Chemical Engineering, University of California, Santa Barbara, California 93106, and Laboratory of Physical Chemistry, Swiss Federal Institute of Technology (ETH), ETH-Hönggerberg, 8093 Zürich, Switzerland
Received: July 8, 2007
In Final Form: October 22, 2007
Abstract:
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 (TPPS4) guest species in the form of J-aggregates.
Amorphous silica prepared similarly and containing TPPS4 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 1H{1H} and 13C{1H} 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.
Download the full text: PDF | HTML
