Ordered hydrophobic organosilicates templated by block copolymers

Hydrophobic organosilicates with controlled morphologies at the nanometer length scale have many potential applications in microelectronics and photonics. Here we report the use of block copolymers of poly(butadiene-b-ethylene oxide) (PB-b-PEO) as templates to create 10-20-nm periodic hexagonal arrays of cylinders in hydrophobic organosilicates. The self-assembly process of the block copolymers is monitored and studied by solid-state NMR, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). It is found that the microstructure and phase behavior of the nanocomposites are very sensitive to the polymer-matrix interface and the intrinsic properties of the block copolymers. When methyltriethoxysilane (MTES) is solely used as sol precursor to swell polymer domains, a disordered structure is always obtained, presumably because MTES changes its nature from hydrophilic to increasingly hydrophobic during curing, and block copolymers are repelled from the matrix. A hydrophilic silicate precursor, (3-glycidyoxypropyl)-trimethoxysilane (GPTS), is introduced as an amphiphilic organosilicate precursor and to preserve the polymer-silicate interface. A layered core-shell structure is formed with PEO and GPTS located at the interface, while PEO and GPTS are microphase separated. Understanding of the templating mechanism may provide a new route for nonlithographic nanopatterning and incorporating functionalities for photonic applications.