Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500°C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35° to 80°C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140°C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water.

Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores

http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

Nanostructured materials: basic concepts and microstructure☆

https://is.muni.cz/el/1431/podzim2006/C7780/um/Read/2711172/SAM_str_grwth_ProgSurfSci00_151.pdf

Structure and growth of self-assembling monolayers

On the Controllable Soft-Templating Approach to Mesoporous Silicates

Living organisms construct various forms of laminated nanocomposites through directed nucleation and growth of inorganics at self-assembled organic templates at temperatures below 100°C and in aqueous solutions. Recent research has focused on the use of functionalized organic surfaces to form continuous thin films of single-phase ceramics. Continuous thin films of mesostructured silicates have also been formed on hydrophobic and hydrophilic surfaces through a two-step mechanism. First, under acidic conditions, surfactant micellar structures are self-assembled at the solid/liquid interface, and second, inorganic precursors condense to form an inorganic-organic nanocomposite. Epitaxial coordination of adsorbed surfactant tubules is observed on mica and graphite substrates, whereas a random arrangement is observed on amorphous silica. The ability to process ceramic-organic nanocomposite films by these methods provides new technological opportunities.

https://science.sciencemag.org/content/sci/273/5277/892.full.pdf

Biomimetic Pathways for Assembling Inorganic Thin Films

We use grazing incidence x-ray scattering to study the molecular structure and morphology of thin (70 ML) crystalline films of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Au(111) surfaces as a function of film thickness, substrate temperature, and growth rate. Although the first two PTCDA monolayers grow in a layer-by-layer fashion, the film evolution beyond the second monolayer depends strongly upon the growth conditions resulting in low-temperature [i.e., nonequilibrium (NEQ)] and high-temperature [equilibrium (EQ)] growth regimes. In the NEQ regime, the films roughen monotonically with increasing film thickness, but retain a well-defined film thickness. Furthermore, we find that these films have a lattice strain which is independent of film thickness. In the EQ regime, the film acquires a three-dimensional morphology for thicknesses g2 ML, and the lattice strain decreases rapidly with increasing thickness. We also show that the transition between the NEQ and EQ regimes is sharp and depends upon the balance between the growth rate and substrate temperature. These results suggest that the PTCDA/Au(111) system is thermodynamically described by incomplete wetting, and that strain and kinetics play an important role in determining molecular organic film characteristics.

L. Zhou

Papers

Biomimetic Pathways for Assembling Inorganic Thin Films

In situ studies of morphology, strain, and growth modes of a molecular organic thin film