Amine-Borane Dehydropolymerisation for the Synthesis and Exploitation of Polyaminoboranes as Routes to New BN-Containing Materials

Polyaminoboranes, -(H2BNHR)n-, are polymers with main-chain B-N backbones that are closely related to polyolefins, -(H2CCHR)n-. However, their fundamental materials and chemical properties are essentially unexplored, despite potential applications as processable precursors to high-performance boron-based ceramics and hex-boron nitride. This is because the challenging combination of efficient and robust organometallic catalyst systems that give polymer of controllable molecular weight and dispersity is missing. However, recent results from the Weller lab have demonstrated a significant advance in understanding and harnessing both organometallic catalyst design and mechanism, and the controlled amine-borane dehydropolymerisation "to order" is now a possibility. The ambitious objectives of this PhD are to develop robust, scalable, routes to bespoke polyaminoboranes, that allows for their wider materials exploitation. New group 9 (Co, Rh, Ir) transition metal catalyst systems will be synthesised and explored for polymer synthesis of exciting new "BN" polymeric materials, through a mechanism-led design strategy. By targeting the desirable metrics of control of polymer chain length and dispersity and cost and practicality of use, catalyst systems that operate on larger scale will be developed. Taking these forward into materials discovery, user friendly methods that allow for the use of these polymers as molecular precursors to new materials will be explored. Low temperature processing will lead to a variety of exciting new "BN" materials where the polymer characteristics (using the catalysts developed) will help define the materials properties of the resulting technologically important materials, especially 3D BN materials: hexagonal boron nitride and boron carbon nitride have very interesting optical, electronic, thermal and chemical properties. There will be a cycle of innovation, with promising leads in materials chemistry leading to the refinement of new and known catalyst systems. The project is collaborative between the groups of Andrew Weller (York, catalysis) and Dr Richard Douthwaite (York, inorganic materials synthesis and characterisation). The PhD student will become expert in a wide range of techniques, that will allow them to develop new organometallic catalyst systems (synthesis), detailed kinetics and mechanism studies, and then take these through to materials synthesis and characterisation. In particular skills will be developed in: organometallic synthesis, elucidation of mechanism in catalysis, NMR spectroscopy, x-ray crystallography and materials synthesis and characterisation techniques. At the end of the PhD the candidate will have broad and deep expertise in a wide range of fundamental, and more applied, organometallic/inorganic materials chemistry techniques.