Silica-based mesostructured and mesoporous materials have sparked much interest among researchers over the last decade [1][2][3][4][5] expanding their functionality by the incorporation of functional organic compounds, [6][7][8] substitution or addition of other inorganic materials, [9] or templating into carbonbased materials.[10] Here we will focus on magnetic mesoporous materials. Although research has been performed on surfactant-based templating and sonochemical approaches to layered iron oxide/oxyhydroxide mesophases, [11,12] polymerderived magnetic bulk ceramics, [13] and bulk iron oxide silicates prepared through sol-gel techniques, [14][15][16][17] research on mesostructured iron-containing silicates is scarce and limited to surfactant-based systems where the iron compound was loaded after synthesis. [18,19] Backfilling the pores is a common technique to functionalize mesoporous materials, [20] but it requires more synthesis and characterization steps and, more importantly, risks clogging the pore structure. We present a simple block-copolymer-based "one-pot" selfassembly approach to multifunctional g-iron oxide aluminosilicates that are mesoporous and exhibit superparamagnetic behavior. Nanoscopic iron oxide particles are incorporated in the walls of the aluminosilicate matrix. Therefore, the blocking of the pores, as observed in earlier studies on backfilled materials, is overcome, even for high iron loadings.[19] We anticipate that this simple and versatile block-copolymerdirected approach to large-pore structures will lead to new techniques for the separation of magnetically labeled biological macromolecules that combine size exclusion as well as magnetic interactions. Also, the robust matrix has thick walls (> 10 nm) which give the material good thermal stability (as high as 800 8C) allowing for catalytic applications at elevated temperatures.The synthesis is unique in allowing for precise control over the structure and composition of the final materials. Although only the inverse-hexagonal cylinder morphology is described (cylindrical pores in a aluminosilicate matrix), several morphologies were observed in our laboratories, similar to those seen for diblock copolymers and their mixtures with homopolymers. [21,22] These morphologies include the hexagonal cylinder (inorganic cylinders in a polymer matrix) and the lamellar phases. The approach can also be extended to other transition-metal oxide systems. Iron oxide was used in our study for its potential magnetic properties, but also serves as an example of what should be possible from a wide range of commercially available metal alkoxides. The actual composition of the resulting materials can be tailored according to the application, which becomes particularly important in catalyst technology.The amphiphilic diblock copolymer, poly(isoprene-blockethylene oxide) (PI-b-PEO), served as a structure-directing agent. Two polymers of different molecular weight and PEO fraction were used (P5: M W = 22 400, 15 wt % PEO; P7: M W = 38 600, 32 wt % PEO). The po...

The routine formation of nanometer-sized structures remains a challenge that limits advances in many fields of nanotechnology. Increasingly ªbottom±upº self-assembly approaches for the nanometer-scale patterning of surfaces are competing with traditional ªtop±downº lithographic processes such as scanned-probe lithography or high-resolution electron-beam (e-beam) lithography. Block copolymer thin films (< 100 nm) are among the more promising materials being examined as they offer ease of processing combined with phase separation induced structure formation on the nanometer scale.Recent work in block copolymer thin film pattern formation has included the use of poly(styrene-block-isoprene) to form periodic structures combined with ozonolysis to remove the isoprene phase, thereby creating arrays of holes in the polymer thin film.[1] In another case, poly(styrene-blockmethyl methacrylate) has been processed in electric fields to align a cylinder phase perpendicular to the film surface, and subsequently exposed to UV light to both mildly crosslink the styrene phase and degrade the methyl methacrylate domains.[2] Similar strategies have been employed to process other block copolymer systems that contain a variety of chemical structures and architectures.[3] Examples of desirable target applications of such porous thin films include photonic bandgap materials, structures to serve as molecular sieves, or templates for magnetic structures.[4]A typical means for improving the processing of bulk polymers is through the use of small-molecule additives.[5] While such additives in bulk polymer structures are ubiquitous, their application in block copolymer thin film processing has not been substantially explored to date. Given the enormous numbers of property variations possible this is surprising. Here we will show several strategies for the use of additivedriven chemistries that take place in only one type of the nanosized domains of block copolymer thin films. We then use such an approach to examine the convergence of ªtop± downº with ªbottom±upº fabrication through light-driven processes.In Figure 1, the structures of the three polymer systems and their respective phase selective additives are introduced. They are: (system 1) poly(a-methyl styrene-b-4-hydroxystyrene) (P(aMS-b-HOST)) and tetramethoxymethyl glycuril (TMMU) with photoacid generator; (system 2) poly(a-methyl styrene-b-isoprene) (P(aMS-b-I)) and 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO); and (system 3) poly(isoprene-b-ethylene oxide), (P(I-b-EO)) and 3-glycidoxypropyltrimethoxysilane/aluminum sec-butoxide (GLYMO)/ Al(O s Bu) 3 . While the first two systems are all-organic, in the case of P(I-b-EO) inorganic additives were used. All polymers were produced using living anionic polymerization, because of its excellent control of architecture and molecular weight (Fig. 1). Films of various controlled thicknesses down to monolayer (see below) were obtained by spin-coating from dilute solution onto silicon wafers.Selection of the appropriate chemistry makes...

In the present study, a poly(isoprene-block-dimethylamino ethyl methacrylate) diblock copolymer (PI-b-PDMAEMA) is used to structure-direct a polysilazane pre-ceramic polymer, commercially known as Ceraset. To the polymer was added a 2-fold excess in weight of the silazane oligomer (Ceraset). The resulting composite was cast into films, and after cooperative self-assembly of block copolymer and Ceraset, the structure was permanently set in the hexagonal columnar morphology, as evidenced by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Cross-linking of the silazane oligomer was achieved with a radical initiator at 120 degrees C. Upon heating of the composite to 1500 degrees C under nitrogen, the structure is preserved and a mesoporous ceramic material is obtained, as demonstrated by SAXS and TEM. The pores are open and accessible, as evidenced by nitrogen sorption/desorption measurements indicating a surface area of about 51 m2 g-1 and a pore diameter of 13 nm, consistent with TEM analysis. These results suggest that the use of block copolymer mesophases may provide a simple, easily controlled pathway for the preparation of various high-temperature ceramic mesostructures.

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Pipe‐dream realized: The as‐made nanocomposite derived from a block‐copolymer‐directed sol–gel synthesis consists of silica networks embedded in an organic matrix. Calcination of the structure at high temperatures gives a final skeletal silica network consistent with the morphology called plumber's nightmare (point group Im$\bar 3$m; see small‐angle X‐ray scattering (SAXS) pattern of an inverse form of this morphology).

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In the present study poly(isoprene-block-ethylene oxide), PI-b-PEO, block copolymers are used to structure iron oxide and silica precursors into reverse mesophases, which upon dissolution of the organic matrix lead to well-defined nanoparticles of spheres, cylinders, and plates based on the original structure of the mesophase prepared. The hybrid mesophases with sphere, cylinder, and lamellar morphologies containing the inorganic components in the minority phases are characterized through a combination of small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and electron energy loss spectroscopy (EELS). After heat treatments the respective nanoparticles on mica surfaces are characterized by scanning force microscopy (SFM). X-ray diffraction (XRD) and superconducting quantum interference device (SQUID) magnetometer measurements are performed to demonstrate that the heat treatment leads to the formation of a magnetic gamma-Fe2O3 crystalline phase within the amorphous aluminosilicate. The results pave the way to functional, i.e., magnetic nanoparticles where the size, shape, and iron oxide concentration can be controlled opening a range of possible applications.

The amphiphilic block copolymer poly(isoprene‐block‐ethylene oxide) was used as a structure‐directing agent for a polysilazane preceramic polymer commercially known as Ceraset. Two block copolymers of different molecular weights and poly(ethylene oxide) weight fractions with body‐centered cubic sphere and hexagonal cylinder morphologies were used. To both polymers, 50 wt % of the silazane oligomer (Ceraset) was added. The resulting composites were cast into films and characterized by small‐angle X‐ray scattering and transmission electron microscopy. The silazane was chemically compatible with the poly(ethylene oxide) microdomains of the block copolymer, and this resulted in a swelling of those domains. After the cooperative self‐assembly of the block copolymer and Ceraset, for both systems the structure was permanently set in the lamellar morphology by the crosslinking of the silazane oligomer with a radical initiator at 120 °C. These results suggest that the use of block copolymer mesophases may provide a simple and easily controlled pathway for the preparation of various high‐temperature SiCN‐type ceramic mesostructures. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3346–3350, 2003