Synthesis and characterization of block copolymer/ceramic precursor nanocomposites based on a polysilazane

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     

Tuning Mechanical Properties of Block Copolymer/Aluminosilicate Hybrid Materials

In this work the primary mechanical property profiles of a specific class of nano‐structured polymer/inorganic hybrid materials are characterized. By utilizing sol‐gel aluminosilicate synthesis with amphiphilic polyisoprene‐block‐poly(ethylene oxide) block copolymers as structure‐directing agents, block copolymer/aluminosilicate hybrid materials are prepared with nanometer scale hexagonally packed cylinders and lamellae of the inorganic hybrid components, as evidenced by small‐angle X‐ray scattering. Systematic thermal and dynamic mechanical analyses are performed on these hybrids as well as on the constituting components. Results reveal two transitions from the low temperature, glassy state of the hybrids into high temperature elastic plateau regions, with moduli that vary over orders of magnitude as a function of composition and morphology. The first transition can be assigned to the glass transition of the PI domains while the second is ascribed to a temperature induced softening of the organic components within the PEO/hybrid domains. The results suggest that in the present nanostructured block copolymer/aluminosilicate hybrid materials composition and morphology provide a powerful tool to tailor mechanical property profiles.