Ordered nanoceramics via block copolymer self-assembly

PMSE 33

Patrick R. L. Malenfant, malenfan@crd.ge.com, Julin Wan, julin.wan@research.ge.com, Seth Taylor, and Mohan Manoharan. Nanotechnology, GE Global Research, K1-4D45, 1 Research Circle, Niskayuna, NY 12309
Self-assembly is a promising method to achieve controlled nanoscale architectures in hybrid materials and ceramics. Here we report the facile synthesis and processing of a new class of block copolymers based on polynorbornene-decaborane. These polymers form ordered organic/inorganic hybrid materials with controlled morphologies via self-assembly while also serving as the ceramic precursor. An interesting solvent dependence on morphology is observed, in which Poly[(norbornene)0.77-b-(norbornenedecaborane)0.3] cast from chloroform solutions led to a lamellar morphology where as polymer cast from tetrahydrofuran provided a cylindrical morphology (polynorbornene-decaborane matrix; polynorbornene cylinders). Moreover, these hybrid materials enable the formation of ordered nanostructured non-oxide ceramics; e.g. pyrolysis of lamellar ordered hybrid block copolymer in nitrogen leads to a layered ceramic nanocomposite of boron carbonitride and carbon. Pyrolysis of ordered hybrid block copolymer with a cylindrical morphology in ammonia yields highly ordered, mesoporous boron nitride having 20 nm diameter pores and surface areas ranging from 700-950 m2/g.